diff mbox series

[v5,1/4] Make linux checkpoints work with multiple inferiors

Message ID 20241210020313.584564-2-kevinb@redhat.com
State New
Headers
Series Make linux checkpoints work with multiple inferiors |

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Commit Message

Kevin Buettner Dec. 10, 2024, 1:54 a.m. UTC 
  The current linux checkpoint code, most of which may be found in
linux-fork.c, is quite broken when attempting to use more than
one inferior.  Running GDB will show internal errors when starting
two inferiors, placing a checkpoint in one, then switching to
the other and doing one of the following commands, "restart",
"detach", "kill", or continue (to program exit).  Test cases
for two of those scenarios may be found in this bug:

    https://sourceware.org/bugzilla/show_bug.cgi?id=31065

I've tested for each of the scenarios and many more in the new
test case, gdb.multi/checkpoint-multi.exp.

I started off with the goal of fixing just those problems, and was
mostly successful with a much smaller patch, but doing "info
checkpoints" with more than one inferior didn't work correctly due to
some of the inferiors being in the wrong program space.  That led me
to making the linux-fork code fully inferior-aware.

Prior to this commit, the list of forks was being maintained in a
global named named 'fork_list'.  I turned this into a per-inferior
data structure.  There was also global named 'highest_fork_num' which
is also now part of the per-inferior struct.  A registry key named
'checkpoint_inferior_data_key' along with function
'get_checkpoint_inferior_data' is used to access the per-inferior
data.  This new function, get_checkpoint_inferior_data, is only
called by the new functions 'fork_list', 'reset_highest_fork_num',
and increment_highest_fork_num, each of which is passed a pointer to
the inferior.  Most occurrences referring to the (previously) global
'fork_list' have been replaced by 'fork_list (inf)'.  In some
functions, where the 'fork_list' is referenced multiple times, a local
named 'fork_list' is declared and initialized instead, like this:

    auto &fork_list = ::fork_list (inf);

The constructor for 'struct fork_info' has gained an additional
parameter.  In addition to passing the pid of the new fork, we now
also pass the fork identifier, fork_num, to the constructor.  This
integer is shown to the user in the "info checkpoints" command and
is provided by the user, perhaps in conjunction with the inferior
number, in commands which manipulate checkpoints, e.g. 'restart' and
'delete checkpoint'.

When checkpoints are used in only one inferior, this commit will
present information to the user and will accept checkpoint identifiers
to commands in much the same way as the code did before this commit.
Per Pedro Alves's recommendations, the "info checkpoints" command has
been changed somewhat.  "info checkpoints" used to display "(main
process)" for the first process in the checkpoint list.  This is no
longer done because it does not provide useful information.  It also
used to display "<running>", when the process is running and no useful
frame information may be displayed.  This has been changed to
"(running)" in order to be more consistent with the output of the
"info threads" command.  A new column has been added to the output for
showing the active process in the output from "info checkpoints".
This column will display 'y' for the active process and 'n' for the
others.  For the active inferior a '*' is also printed preceding the
checkpoint identifier.  Here's what things look(ed) like before and
after for just one inferior:

Before:

(gdb) info checkpoints
* 0 Thread 0x7ffff7cd3740 (LWP 84201) (main process) at 0x40114a, file hello.c, line 28
  1 process 84205 at 0x401199, file hello.c, line 51
  2 process 84206 at 0x4011a3, file hello.c, line 53

After:

(gdb) info checkpoints
  Id Active Target Id      Frame
*  0 y      process 551311 at 0x40114a, file hello.c, line 28
   1 n      process 551314 at 0x401199, file hello.c, line 51
   2 n      process 551315 at 0x4011a3, file hello.c, line 53

(The Thread versus process distinction is handled by another
patch - the "After" example assumes that patch is applied too.)

When there are multiple inferiors, the "info checkpoints" output looks
like this:

(gdb) info checkpoints
  Id  Active Target Id      Frame
  1.0 y      process 535276 at 0x401199, file hello.c, line 51
  1.1 n      process 535283 at 0x401199, file hello.c, line 51
  1.2 n      process 535288 at 0x401199, file hello.c, line 51
  2.1 n      process 535280 at 0x401258, file goodbye.c, line 62
  2.2 y      process 535284 at 0x401258, file goodbye.c, line 62
* 3.0 y      process 535285 at 0x40115c, file hangout.c, line 31
  3.2 n      process 535287 at 0x40115c, file hangout.c, line 31

A new function named 'parse_checkpoint_id' has been added.  As its
name suggests, it's responsible for parsing a string representing a
checkpoint identifier.  These identifiers may be either a decimal
number representing the checkpoint number in the current inferior or
two decimal numbers separated by '.', in which case the first is the
inferior number and the second is the checkpoint number in that
inferior.  It is called by delete_checkpoint_command,
detach_checkpoint_command, info_checkpoints_command, and
restart_command.  Calls to 'parse_checkpoint_id' replace calls to
'parse_and_eval_long', plus error checking and error reporting code
near the calls to 'parse_and_eval_long'.  As such, error checking and
reporting has been consolidated into a single function and the
messages output are more uniform, though this has necessitated changes
to the existing test case gdb.base/checkpoint.exp.

The functions 'find_fork_ptid' and 'find_fork_pid' used to return a
pointer to a fork_info struct.  They now return a pair consisting of
the pointer to a fork_info struct in addition to a pointer to the
inferior containing that checkpoint.

'find_fork_id' returns a pointer to a fork_info struct just as it did
before, but it's now gained a new parameter, 'inf', which is the
inferior in which to look.

info_checkpoints_command used to simply iterate over the list of
forks (checkpoints), printing each one out.  It now needs to iterate
over all inferiors and, for those which have checkpoints, it needs
to iterate over the list of checkpoints in that inferior.  As noted
earlier, the format of the output has been changed so that checkpoint
identifiers incorporating an inferior number may be printed.

linux_fork_context, called by restart_command, now contains code to
switch inferiors when the fork being restarted is in an inferior which
is different from the current one.  The scoped_switch_fork_info class
now also contains code for switching inferiors in both the constructor
and destructor.

gdb/linux-nat.c has a few changes.  All but one of them are related
to passing the inferior to one of the linux-fork functions.  But
one of the tests in linux_nat_target::detach has also changed in
a non-obvious way.  In attempting to determine whether to call
linux_fork_detach(), that code used to do:

  if (pid == inferior_ptid.pid () && forks_exist_p ())

It's been simplified to:

  if (forks_exist_p (inf))

I had added the 'pid == inferior_ptid.pid ()' condition in late 2023
while working on a detach bug.  It was kind of a hack to prevent
calling linux_fork_detach() when in a different inferior.  That's no
longer needed since the call to forks_exist_p does this directly -
i.e. it is now inferior-aware.

Finally, the header file 'linux-fork.h' has been updated to reflect
the fact that add_fork, linux_fork_killall, linux_fork_detach, and
forks_exist_p all now require that a pointer to an inferior be passed
to these functions.  Additionally (as mentioned earlier),
find_fork_pid now returns std::pair<fork_info *, inferior *> instead
'of fork_info *'.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31065
---
 gdb/linux-fork.c                             | 557 +++++++++----
 gdb/linux-fork.h                             |  15 +-
 gdb/linux-nat.c                              |  18 +-
 gdb/testsuite/gdb.base/checkpoint.exp        |  24 +-
 gdb/testsuite/gdb.multi/checkpoint-multi.exp | 800 +++++++++++++++++++
 5 files changed, 1230 insertions(+), 184 deletions(-)
 create mode 100644 gdb/testsuite/gdb.multi/checkpoint-multi.exp
diff mbox series

Patch

diff --git a/gdb/linux-fork.c b/gdb/linux-fork.c
index 7d3505b5948..49c2cf1ed84 100644
--- a/gdb/linux-fork.c
+++ b/gdb/linux-fork.c
@@ -29,6 +29,7 @@ 
 #include "linux-nat.h"
 #include "gdbthread.h"
 #include "source.h"
+#include "progspace-and-thread.h"
 
 #include "nat/gdb_ptrace.h"
 #include "gdbsupport/gdb_wait.h"
@@ -40,10 +41,11 @@ 
 #include <list>
 
 /* Fork list data structure:  */
+
 struct fork_info
 {
-  explicit fork_info (pid_t pid)
-    : ptid (pid, pid)
+  explicit fork_info (pid_t pid, int fork_num)
+    : ptid (pid, pid), num (fork_num)
   {
   }
 
@@ -71,7 +73,7 @@  struct fork_info
   ptid_t parent_ptid = null_ptid;
 
   /* Convenient handle (GDB fork id).  */
-  int num = 0;
+  int num;
 
   /* Convenient for info fork, saves having to actually switch
      contexts.  */
@@ -85,115 +87,247 @@  struct fork_info
   int maxfd = 0;
 };
 
-static std::list<fork_info> fork_list;
-static int highest_fork_num;
+/* Per-inferior checkpoint data.  */
+
+struct checkpoint_inferior_data
+{
+  /* List of forks (checkpoints) in particular inferior.  Once a
+     checkpoint has been created, fork_list will contain at least two
+     items, the first in the list will be the original (or, if not
+     original, then the oldest) fork.  */
+  std::list<fork_info> fork_list;
+
+  /* Most recently assigned fork number; when 0, no checkpoints have
+     been created yet.  */
+  int highest_fork_num = 0;
+};
+
+/* Per-inferior data key.  */
+
+static const registry<inferior>::key<checkpoint_inferior_data>
+  checkpoint_inferior_data_key;
+
+/* Fetch per-inferior checkpoint data.  It always returns a valid pointer
+   to a checkpoint_inferior_info struct.  */
+
+static struct checkpoint_inferior_data *
+get_checkpoint_inferior_data (struct inferior *inf)
+{
+  struct checkpoint_inferior_data *data;
+
+  data = checkpoint_inferior_data_key.get (inf);
+  if (data == nullptr)
+    data = checkpoint_inferior_data_key.emplace (inf);
+
+  return data;
+}
+
+/* Return a reference to the per-inferior fork list.  */
+
+static std::list<fork_info> &
+fork_list (inferior *inf)
+{
+  return get_checkpoint_inferior_data (inf)->fork_list;
+}
+
+/* Increment the highest fork number for inferior INF, returning
+   the new value.  */
+
+static int
+increment_highest_fork_num (inferior *inf)
+{
+  return ++get_checkpoint_inferior_data (inf)->highest_fork_num;
+}
+
+/* Reset the highest fork number for inferior INF.  */
+
+static void
+reset_highest_fork_num (inferior *inf)
+{
+  get_checkpoint_inferior_data (inf)->highest_fork_num = 0;
+}
 
 /* Fork list methods:  */
 
-int
-forks_exist_p (void)
+/* Predicate which returns true if checkpoint(s) exist in the inferior
+   INF, false otherwise.  */
+
+bool
+forks_exist_p (inferior *inf)
 {
-  return !fork_list.empty ();
+  /* Avoid allocating checkpoint_inferior_data storage by checking
+     to see if such storage exists prior to calling fork_list.
+     If we just call fork_list alone, then that call will create
+     this storage, even for inferiors which don't need it.  */
+  return (checkpoint_inferior_data_key.get (inf) != nullptr
+	  && !fork_list (inf).empty ());
 }
 
-/* Return the last fork in the list.  */
+/* Return the last fork in the list for inferior INF.  */
 
 static struct fork_info *
-find_last_fork (void)
+find_last_fork (inferior *inf)
 {
+  auto &fork_list = ::fork_list (inf);
+
   if (fork_list.empty ())
     return NULL;
 
   return &fork_list.back ();
 }
 
-/* Return true iff there's one fork in the list.  */
+/* Return true iff there's one fork in the list for inferior INF.  */
 
 static bool
-one_fork_p ()
+one_fork_p (inferior *inf)
 {
-  return fork_list.size () == 1;
+  return fork_list (inf).size () == 1;
 }
 
 /* Add a new fork to the internal fork list.  */
 
 void
-add_fork (pid_t pid)
+add_fork (pid_t pid, inferior *inf)
 {
-  fork_list.emplace_back (pid);
-
-  if (one_fork_p ())
-    highest_fork_num = 0;
-
-  fork_info *fp = &fork_list.back ();
-  fp->num = ++highest_fork_num;
+  fork_list (inf).emplace_back (pid, increment_highest_fork_num (inf));
 }
 
+/* Delete a fork for PTID in inferior INF.  When the last fork is
+   deleted, HIGHEST_FORK_NUM for the given inferior is reset to 0.
+   The fork list may also be made to be empty when only one fork
+   remains.  */
+
 static void
-delete_fork (ptid_t ptid)
+delete_fork (ptid_t ptid, inferior *inf)
 {
   linux_target->low_forget_process (ptid.pid ());
 
+  auto &fork_list = ::fork_list (inf);
   for (auto it = fork_list.begin (); it != fork_list.end (); ++it)
     if (it->ptid == ptid)
       {
 	fork_list.erase (it);
 
+	if (fork_list.empty ())
+	  reset_highest_fork_num (inf);
+
 	/* Special case: if there is now only one process in the list,
 	   and if it is (hopefully!) the current inferior_ptid, then
 	   remove it, leaving the list empty -- we're now down to the
 	   default case of debugging a single process.  */
-	if (one_fork_p () && fork_list.front ().ptid == inferior_ptid)
+	if (one_fork_p (inf) && fork_list.front ().ptid == inferior_ptid)
 	  {
 	    /* Last fork -- delete from list and handle as solo
 	       process (should be a safe recursion).  */
-	    delete_fork (inferior_ptid);
+	    delete_fork (inferior_ptid, inf);
 	  }
 	return;
       }
 }
 
-/* Find a fork_info by matching PTID.  */
-static struct fork_info *
+/* Find a fork_info and inferior by matching PTID.  */
+
+static std::pair<fork_info *, inferior *>
 find_fork_ptid (ptid_t ptid)
 {
-  for (fork_info &fi : fork_list)
-    if (fi.ptid == ptid)
-      return &fi;
+  for (inferior *inf : all_inferiors (linux_target))
+    {
+      for (fork_info &fi : fork_list (inf))
+	if (fi.ptid == ptid)
+	  return { &fi, inf };
+    }
 
-  return NULL;
+  return { nullptr, nullptr };
 }
 
-/* Find a fork_info by matching ID.  */
-static struct fork_info *
-find_fork_id (int num)
+/* Find a fork_info by matching NUM in inferior INF.  */
+
+static fork_info *
+find_fork_id (inferior *inf, int num)
 {
-  for (fork_info &fi : fork_list)
+  for (fork_info &fi : fork_list (inf))
     if (fi.num == num)
       return &fi;
 
-  return NULL;
+  return nullptr;
 }
 
-/* Find a fork_info by matching pid.  */
-extern struct fork_info *
+/* Find a fork_info and inferior by matching pid.  */
+
+extern std::pair<fork_info *, inferior *>
 find_fork_pid (pid_t pid)
 {
-  for (fork_info &fi : fork_list)
-    if (pid == fi.ptid.pid ())
-      return &fi;
+  for (inferior *inf : all_inferiors (linux_target))
+    {
+      for (fork_info &fi : fork_list (inf))
+	if (pid == fi.ptid.pid ())
+	  return { &fi, inf };
+    }
 
-  return NULL;
+  return { nullptr, nullptr };
 }
 
-static ptid_t
-fork_id_to_ptid (int num)
+/* Parse a command argument representing a checkpoint id.  This
+   can take one of two forms:
+
+   Num
+
+   -or-
+
+   Inf.Num
+
+   where Num is a non-negative decimal integer and Inf, if present, is
+   a positive decimal integer.
+
+   Return a pair with a pointer to the fork_info struct and pointer
+   to the inferior.  This function will throw an error if there's
+   a problem with the parsing or if either the inferior or checkpoint
+   id does not exist. */
+
+static std::pair<fork_info *, inferior *>
+parse_checkpoint_id (const char *ckptstr)
 {
-  struct fork_info *fork = find_fork_id (num);
-  if (fork)
-    return fork->ptid;
+  const char *number = ckptstr;
+  const char *p1;
+  struct inferior *inf;
+
+  const char *dot = strchr (number, '.');
+
+  if (dot != nullptr)
+    {
+      /* Parse number to the left of the dot.  */
+      int inf_num;
+
+      p1 = number;
+      inf_num = get_number_trailer (&p1, '.');
+      if (inf_num <= 0)
+	error (_("Inferior number must be a positive integer"));
+
+      inf = find_inferior_id (inf_num);
+      if (inf == NULL)
+	error (_("No inferior number '%d'"), inf_num);
+
+      p1 = dot + 1;
+    }
   else
-    return ptid_t (-1);
+    {
+      inf = current_inferior ();
+      p1 = number;
+    }
+
+  int fork_num = get_number_trailer (&p1, 0);
+  if (fork_num < 0)
+    error (_("Checkpoint number must be a non-negative integer"));
+
+  if (!forks_exist_p (inf))
+    error (_("Inferior %d has no checkpoints"), inf->num);
+
+  fork_info *fork_ptr = find_fork_id (inf, fork_num);
+  if (fork_ptr == nullptr)
+    error (_("Invalid checkpoint number %d for inferior %d"),
+	   fork_num, inf->num);
+
+  return { fork_ptr, inf };
 }
 
 /* Fork list <-> gdb interface.  */
@@ -298,7 +432,7 @@  fork_save_infrun_state (struct fork_info *fp)
 /* Kill 'em all, let God sort 'em out...  */
 
 void
-linux_fork_killall (void)
+linux_fork_killall (inferior *inf)
 {
   /* Walk list and kill every pid.  No need to treat the
      current inferior_ptid as special (we do not return a
@@ -306,6 +440,7 @@  linux_fork_killall (void)
      or a parent, so may get a SIGCHLD from a previously
      killed child.  Wait them all out.  */
 
+  auto &fork_list = ::fork_list (inf);
   for (fork_info &fi : fork_list)
     {
       pid_t pid = fi.ptid.pid ();
@@ -324,6 +459,7 @@  linux_fork_killall (void)
 
   /* Clear list, prepare to start fresh.  */
   fork_list.clear ();
+  reset_highest_fork_num (inf);
 }
 
 /* The current inferior_ptid has exited, but there are other viable
@@ -331,10 +467,11 @@  linux_fork_killall (void)
    first available.  */
 
 void
-linux_fork_mourn_inferior (void)
+linux_fork_mourn_inferior ()
 {
   struct fork_info *last;
   int status;
+  inferior *inf = current_inferior ();
 
   /* Wait just one more time to collect the inferior's exit status.
      Do not check whether this succeeds though, since we may be
@@ -343,23 +480,23 @@  linux_fork_mourn_inferior (void)
   gdb::waitpid (inferior_ptid.pid (), &status, 0);
 
   /* OK, presumably inferior_ptid is the one who has exited.
-     We need to delete that one from the fork_list, and switch
+     We need to delete that one from the fork list, and switch
      to the next available fork.  */
-  delete_fork (inferior_ptid);
+  delete_fork (inferior_ptid, inf);
 
   /* There should still be a fork - if there's only one left,
      delete_fork won't remove it, because we haven't updated
      inferior_ptid yet.  */
-  gdb_assert (!fork_list.empty ());
+  gdb_assert (!fork_list (inf).empty ());
 
-  last = find_last_fork ();
+  last = find_last_fork (inf);
   fork_load_infrun_state (last);
   gdb_printf (_("[Switching to %s]\n"),
 	      target_pid_to_str (inferior_ptid).c_str ());
 
   /* If there's only one fork, switch back to non-fork mode.  */
-  if (one_fork_p ())
-    delete_fork (inferior_ptid);
+  if (one_fork_p (inf))
+    delete_fork (inferior_ptid, inf);
 }
 
 /* The current inferior_ptid is being detached, but there are other
@@ -367,13 +504,13 @@  linux_fork_mourn_inferior (void)
    the first available.  */
 
 void
-linux_fork_detach (int from_tty, lwp_info *lp)
+linux_fork_detach (int from_tty, lwp_info *lp, inferior *inf)
 {
   gdb_assert (lp != nullptr);
   gdb_assert (lp->ptid == inferior_ptid);
 
   /* OK, inferior_ptid is the one we are detaching from.  We need to
-     delete it from the fork_list, and switch to the next available
+     delete it from the fork list, and switch to the next available
      fork.  But before doing the detach, do make sure that the lwp
      hasn't exited or been terminated first.  */
 
@@ -386,11 +523,12 @@  linux_fork_detach (int from_tty, lwp_info *lp)
 	       target_pid_to_str (inferior_ptid).c_str ());
     }
 
-  delete_fork (inferior_ptid);
+  delete_fork (inferior_ptid, inf);
 
   /* There should still be a fork - if there's only one left,
      delete_fork won't remove it, because we haven't updated
      inferior_ptid yet.  */
+  auto &fork_list = ::fork_list (inf);
   gdb_assert (!fork_list.empty ());
 
   fork_load_infrun_state (&fork_list.front ());
@@ -400,8 +538,8 @@  linux_fork_detach (int from_tty, lwp_info *lp)
 		target_pid_to_str (inferior_ptid).c_str ());
 
   /* If there's only one fork, switch back to non-fork mode.  */
-  if (one_fork_p ())
-    delete_fork (inferior_ptid);
+  if (one_fork_p (inf))
+    delete_fork (inferior_ptid, inf);
 }
 
 /* Temporarily switch to the infrun state stored on the fork_info
@@ -414,19 +552,26 @@  class scoped_switch_fork_info
   /* Switch to the infrun state held on the fork_info identified by
      PPTID.  If PPTID is the current inferior then no switch is done.  */
   explicit scoped_switch_fork_info (ptid_t pptid)
-    : m_oldfp (nullptr)
+    : m_oldfp (nullptr), m_oldinf (nullptr)
   {
     if (pptid != inferior_ptid)
       {
-	struct fork_info *newfp = nullptr;
-
 	/* Switch to pptid.  */
-	m_oldfp = find_fork_ptid (inferior_ptid);
+	auto [oldfp, oldinf] = find_fork_ptid (inferior_ptid);
+	m_oldfp = oldfp;
 	gdb_assert (m_oldfp != nullptr);
-	newfp = find_fork_ptid (pptid);
+	auto [newfp, newinf]  = find_fork_ptid (pptid);
 	gdb_assert (newfp != nullptr);
 	fork_save_infrun_state (m_oldfp);
 	remove_breakpoints ();
+
+	if (oldinf != newinf)
+	  {
+	    thread_info *tp = any_thread_of_inferior (newinf);
+	    switch_to_thread (tp);
+	    m_oldinf = oldinf;
+	  }
+
 	fork_load_infrun_state (newfp);
 	insert_breakpoints ();
       }
@@ -436,12 +581,17 @@  class scoped_switch_fork_info
      didn't need to switch states, then nothing is done here either.  */
   ~scoped_switch_fork_info ()
   {
-    if (m_oldfp != nullptr)
+    if (m_oldinf != nullptr || m_oldfp != nullptr)
       {
 	/* Switch back to inferior_ptid.  */
 	try
 	  {
 	    remove_breakpoints ();
+	    if (m_oldinf != nullptr)
+	      {
+		thread_info *tp = any_thread_of_inferior (m_oldinf);
+		switch_to_thread (tp);
+	      }
 	    fork_load_infrun_state (m_oldfp);
 	    insert_breakpoints ();
 	  }
@@ -473,8 +623,16 @@  class scoped_switch_fork_info
      we were already in the desired state, and nothing needs to be
      restored.  */
   struct fork_info *m_oldfp;
+
+  /* When switching to a different fork, this is the inferior for the
+     fork that we're switching from, and to which we'll switch back once
+     end-of-scope is reached.  It may also be nullptr if no switching
+     is required.  */
+  inferior *m_oldinf;
 };
 
+/* Call waitpid() by making an inferior function call.  */
+
 static int
 inferior_call_waitpid (ptid_t pptid, int pid)
 {
@@ -517,30 +675,25 @@  static void
 delete_checkpoint_command (const char *args, int from_tty)
 {
   ptid_t ptid, pptid;
-  struct fork_info *fi;
 
   if (!args || !*args)
     error (_("Requires argument (checkpoint id to delete)"));
 
-  ptid = fork_id_to_ptid (parse_and_eval_long (args));
-  if (ptid == minus_one_ptid)
-    error (_("No such checkpoint id, %s"), args);
+  auto [fi, inf] = parse_checkpoint_id (args);
+  ptid = fi->ptid;
+  gdb_assert (fi != nullptr);
+  pptid = fi->parent_ptid;
 
-  if (ptid == inferior_ptid)
-    error (_("\
-Please switch to another checkpoint before deleting the current one"));
+  if (ptid.pid () == inf->pid)
+    error (_("Cannot delete active checkpoint"));
 
   if (ptrace (PTRACE_KILL, ptid.pid (), 0, 0))
     error (_("Unable to kill pid %s"), target_pid_to_str (ptid).c_str ());
 
-  fi = find_fork_ptid (ptid);
-  gdb_assert (fi);
-  pptid = fi->parent_ptid;
-
   if (from_tty)
     gdb_printf (_("Killed %s\n"), target_pid_to_str (ptid).c_str ());
 
-  delete_fork (ptid);
+  delete_fork (ptid, inf);
 
   if (pptid == null_ptid)
     {
@@ -558,7 +711,7 @@  Please switch to another checkpoint before deleting the current one"));
      If fi->parent_ptid is a part of lwp and it is stopped, waitpid the
      ptid.  */
   thread_info *parent = linux_target->find_thread (pptid);
-  if ((parent == NULL && find_fork_ptid (pptid))
+  if ((parent == NULL && find_fork_ptid (pptid).first != nullptr)
       || (parent != NULL && parent->state == THREAD_STOPPED))
     {
       if (inferior_call_waitpid (pptid, ptid.pid ()))
@@ -575,9 +728,8 @@  detach_checkpoint_command (const char *args, int from_tty)
   if (!args || !*args)
     error (_("Requires argument (checkpoint id to detach)"));
 
-  ptid = fork_id_to_ptid (parse_and_eval_long (args));
-  if (ptid == minus_one_ptid)
-    error (_("No such checkpoint id, %s"), args);
+  auto [fi, inf] = parse_checkpoint_id (args);
+  ptid = fi->ptid;
 
   if (ptid == inferior_ptid)
     error (_("\
@@ -589,7 +741,7 @@  Please switch to another checkpoint before detaching the current one"));
   if (from_tty)
     gdb_printf (_("Detached %s\n"), target_pid_to_str (ptid).c_str ());
 
-  delete_fork (ptid);
+  delete_fork (ptid, current_inferior ());
 }
 
 /* Print information about currently known checkpoints.  */
@@ -598,70 +750,139 @@  static void
 info_checkpoints_command (const char *arg, int from_tty)
 {
   struct gdbarch *gdbarch = get_current_arch ();
-  int requested = -1;
-  bool printed = false;
+  struct inferior *cur_inf = current_inferior ();
+  inferior *req_inf = nullptr;
+  fork_info *req_fi = nullptr;
+  bool will_print_something = false;
 
   if (arg && *arg)
-    requested = (int) parse_and_eval_long (arg);
+    std::tie (req_fi, req_inf) = parse_checkpoint_id (arg);
+
+  /* Figure out whether to print the inferior number in the
+     checkpoint list.  */
+  bool print_inf = (number_of_inferiors () > 1);
 
-  for (const fork_info &fi : fork_list)
+  /* Compute widths of some of the table components.  */
+  size_t inf_width = 0;
+  size_t num_width = 0;
+  size_t targid_width = 0;
+  for (inferior *inf : all_inferiors (linux_target))
     {
-      if (requested > 0 && fi.num != requested)
+      if (req_inf != nullptr && req_inf != inf)
 	continue;
-      printed = true;
 
-      bool is_current = fi.ptid == inferior_ptid;
-      if (is_current)
-	gdb_printf ("* ");
-      else
-	gdb_printf ("  ");
+      scoped_restore_current_pspace_and_thread restore_pspace_thread;
+      switch_to_program_space_and_thread (inf->pspace);
 
-      gdb_printf ("%d %s", fi.num, target_pid_to_str (fi.ptid).c_str ());
-      if (fi.num == 0)
-	gdb_printf (_(" (main process)"));
-
-      if (is_current && inferior_thread ()->state == THREAD_RUNNING)
+      for (const fork_info &fi : fork_list (inf))
 	{
-	  gdb_printf (_(" <running>\n"));
-	  continue;
-	}
-
-      gdb_printf (_(" at "));
-      ULONGEST pc
-	= (is_current
-	   ? regcache_read_pc (get_thread_regcache (inferior_thread ()))
-	   : fi.pc);
-      gdb_puts (paddress (gdbarch, pc));
-
-      symtab_and_line sal = find_pc_line (pc, 0);
-      if (sal.symtab)
-	gdb_printf (_(", file %s"),
-		    symtab_to_filename_for_display (sal.symtab));
-      if (sal.line)
-	gdb_printf (_(", line %d"), sal.line);
-      if (!sal.symtab && !sal.line)
-	{
-	  bound_minimal_symbol msym = lookup_minimal_symbol_by_pc (pc);
-	  if (msym.minsym)
-	    gdb_printf (", <%s>", msym.minsym->linkage_name ());
+	  if (req_fi != nullptr && req_fi != &fi)
+	    continue;
+
+	  will_print_something = true;
+
+	  inf_width
+	    = std::max (inf_width,
+			string_printf ("%d", inf->num).size ());
+	  num_width
+	    = std::max (num_width,
+		        string_printf ("%d", fi.num).size ()
+			  + (print_inf ? 1 : 0));
+	  targid_width
+	    = std::max (targid_width,
+			target_pid_to_str (fi.ptid).size ());
 	}
+    }
 
-      gdb_putc ('\n');
+  /* Return early if there are no checkpoints to print.  */
+  if (!will_print_something)
+    {
+      gdb_printf (_("No checkpoints.\n"));
+      return;
     }
 
-  if (!printed)
+  /* Ensure that column header width doesn't exceed that of the column data
+     for the Id field.  */
+  if (!print_inf && num_width < 2)
+    num_width = 2;
+
+  /* Print column headers...  */
+  gdb_printf ("  ");
+  gdb_printf ("%-*s", (print_inf ? (int) inf_width : 0) 
+		      + (int) num_width + 1, "Id");
+  gdb_printf ("Active ");
+  gdb_printf ("%-*s", (int) targid_width + 1, "Target Id");
+  gdb_printf ("Frame\n");
+
+  /* Print each checkpoint padded, as needed, with spaces so that everything
+     lines up.  */
+  for (inferior *inf : all_inferiors (linux_target))
     {
-      if (requested > 0)
-	gdb_printf (_("No checkpoint number %d.\n"), requested);
-      else
-	gdb_printf (_("No checkpoints.\n"));
+      if (req_inf != nullptr && req_inf != inf)
+	continue;
+
+      scoped_restore_current_pspace_and_thread restore_pspace_thread;
+      switch_to_program_space_and_thread (inf->pspace);
+
+      for (const fork_info &fi : fork_list (inf))
+	{
+	  if (req_fi != nullptr && req_fi != &fi)
+	    continue;
+
+	  thread_info *t = any_thread_of_inferior (inf);
+	  bool is_current = fi.ptid.pid () == inf->pid;
+	  if (is_current && cur_inf == inf)
+	    gdb_printf ("* ");
+	  else
+	    gdb_printf ("  ");
+
+	  if (print_inf)
+	    gdb_printf ("%*d.%-*d", (int) inf_width, inf->num,
+				    (int) num_width, fi.num);
+	  else
+	    gdb_printf ("%*d ", (int) num_width, fi.num);
+
+	  /* Print out 'y' or 'n' for whether the checkpoint is current.  */
+	  gdb_printf ("%-7s", is_current ? "y" : "n");
+
+	  /* Print target id.  */
+	  gdb_printf ("%-*s", (int) targid_width,
+		      target_pid_to_str (fi.ptid).c_str ());
+
+	  if (t->state == THREAD_RUNNING && is_current)
+	    gdb_printf (_(" (running)"));
+	  else
+	    {
+	      gdb_printf (_(" at "));
+	      ULONGEST pc
+		= (is_current
+		   ? regcache_read_pc (get_thread_regcache (t))
+		   : fi.pc);
+	      gdb_puts (paddress (gdbarch, pc));
+
+	      symtab_and_line sal = find_pc_line (pc, 0);
+	      if (sal.symtab)
+		gdb_printf (_(", file %s"),
+			    symtab_to_filename_for_display (sal.symtab));
+	      if (sal.line)
+		gdb_printf (_(", line %d"), sal.line);
+	      if (!sal.symtab && !sal.line)
+		{
+		  bound_minimal_symbol msym = lookup_minimal_symbol_by_pc (pc);
+		  if (msym.minsym)
+		    gdb_printf (", <%s>", msym.minsym->linkage_name ());
+		}
+	    }
+
+	  gdb_putc ('\n');
+	}
     }
 }
 
 /* The PID of the process we're checkpointing.  */
 static int checkpointing_pid = 0;
 
-int
+bool
 linux_fork_checkpointing_p (int pid)
 {
   return (checkpointing_pid == pid);
@@ -691,17 +912,16 @@  checkpoint_command (const char *args, int from_tty)
   struct target_waitstatus last_target_waitstatus;
   ptid_t last_target_ptid;
   struct value *fork_fn = NULL, *ret;
-  struct fork_info *fp;
   pid_t retpid;
 
-  if (!target_has_execution ()) 
+  if (!target_has_execution ())
     error (_("The program is not being run."));
 
   /* Ensure that the inferior is not multithreaded.  */
   update_thread_list ();
   if (inf_has_multiple_threads ())
     error (_("checkpoint: can't checkpoint multiple threads."));
-  
+
   /* Make the inferior fork, record its (and gdb's) state.  */
 
   if (lookup_minimal_symbol (current_program_space, "fork").minsym != nullptr)
@@ -730,14 +950,21 @@  checkpoint_command (const char *args, int from_tty)
   retpid = value_as_long (ret);
   get_last_target_status (nullptr, &last_target_ptid, &last_target_waitstatus);
 
-  fp = find_fork_pid (retpid);
+  auto [fp, inf] = find_fork_pid (retpid);
+
+  if (!fp)
+    error (_("Failed to find new fork"));
 
   if (from_tty)
     {
       int parent_pid;
 
-      gdb_printf (_("checkpoint %d: fork returned pid %ld.\n"),
-		  fp != NULL ? fp->num : -1, (long) retpid);
+      gdb_printf (_("checkpoint %s: fork returned pid %ld.\n"),
+		  ((number_of_inferiors () > 1)
+		   ? string_printf ("%d.%d", inf->num, fp->num).c_str ()
+		   : string_printf ("%d", fp->num).c_str ()),
+		 (long) retpid);
+
       if (info_verbose)
 	{
 	  parent_pid = last_target_ptid.lwp ();
@@ -748,15 +975,12 @@  checkpoint_command (const char *args, int from_tty)
 	}
     }
 
-  if (!fp)
-    error (_("Failed to find new fork"));
-
-  if (one_fork_p ())
+  if (one_fork_p (inf))
     {
       /* Special case -- if this is the first fork in the list (the
-	 list was hitherto empty), then add inferior_ptid first, as a
-	 special zeroeth fork id.  */
-      fork_list.emplace_front (inferior_ptid.pid ());
+	 list was hitherto empty), then add inferior_ptid as a special
+	 zeroeth fork id.  */
+      fork_list (inf).emplace_front (inferior_ptid.pid (), 0);
     }
 
   fork_save_infrun_state (fp);
@@ -764,40 +988,57 @@  checkpoint_command (const char *args, int from_tty)
 }
 
 static void
-linux_fork_context (struct fork_info *newfp, int from_tty)
+linux_fork_context (struct fork_info *newfp, int from_tty, inferior *newinf)
 {
-  /* Now we attempt to switch processes.  */
-  struct fork_info *oldfp;
+  bool inferior_changed = false;
 
+  /* Now we attempt to switch processes.  */
   gdb_assert (newfp != NULL);
 
-  oldfp = find_fork_ptid (inferior_ptid);
-  gdb_assert (oldfp != NULL);
+  if (newinf != current_inferior ())
+    {
+      thread_info *tp = any_thread_of_inferior (newinf);
+      switch_to_thread (tp);
+      inferior_changed = true;
+    }
 
-  fork_save_infrun_state (oldfp);
-  remove_breakpoints ();
-  fork_load_infrun_state (newfp);
-  insert_breakpoints ();
+  auto [oldfp, oldinf] = find_fork_ptid (inferior_ptid);
+  gdb_assert (oldfp != NULL);
 
-  gdb_printf (_("Switching to %s\n"),
-	      target_pid_to_str (inferior_ptid).c_str ());
+  if (oldfp != newfp)
+    {
+      fork_save_infrun_state (oldfp);
+      remove_breakpoints ();
+      fork_load_infrun_state (newfp);
+      insert_breakpoints ();
+      if (!inferior_changed)
+	gdb_printf (_("Switching to %s\n"),
+		    target_pid_to_str (inferior_ptid).c_str ());
+    }
 
-  print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC, 1);
+  notify_user_selected_context_changed
+    (inferior_changed ? (USER_SELECTED_INFERIOR | USER_SELECTED_FRAME)
+		      : USER_SELECTED_FRAME);
 }
 
 /* Switch inferior process (checkpoint) context, by checkpoint id.  */
+
 static void
 restart_command (const char *args, int from_tty)
 {
-  struct fork_info *fp;
-
   if (!args || !*args)
     error (_("Requires argument (checkpoint id to restart)"));
 
-  if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
-    error (_("Not found: checkpoint id %s"), args);
+  auto [fp, inf] = parse_checkpoint_id (args);
+
+  /* Don't allow switching from a thread/fork that's running.  */
+  inferior *curinf = current_inferior ();
+  if (curinf->pid != 0
+      && any_thread_of_inferior (curinf)->state == THREAD_RUNNING)
+    error (_("Cannot execute this command while "
+	     "the selected thread is running."));
 
-  linux_fork_context (fp, from_tty);
+  linux_fork_context (fp, from_tty, inf);
 }
 
 void _initialize_linux_fork ();
diff --git a/gdb/linux-fork.h b/gdb/linux-fork.h
index c553aaf0740..0ed47eda15f 100644
--- a/gdb/linux-fork.h
+++ b/gdb/linux-fork.h
@@ -22,12 +22,13 @@ 
 
 struct fork_info;
 struct lwp_info;
-extern void add_fork (pid_t);
-extern struct fork_info *find_fork_pid (pid_t);
-extern void linux_fork_killall (void);
-extern void linux_fork_mourn_inferior (void);
-extern void linux_fork_detach (int, lwp_info *);
-extern int forks_exist_p (void);
-extern int linux_fork_checkpointing_p (int);
+class inferior;
+extern void add_fork (pid_t, inferior *inf);
+extern std::pair<fork_info *, inferior *> find_fork_pid (pid_t);
+extern void linux_fork_killall (inferior *inf);
+extern void linux_fork_mourn_inferior ();
+extern void linux_fork_detach (int, lwp_info *, inferior *inf);
+extern bool forks_exist_p (inferior *inf);
+extern bool linux_fork_checkpointing_p (int);
 
 #endif /* LINUX_FORK_H */
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 3f252370c7b..5b2cc8f2fb8 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1558,13 +1558,13 @@  linux_nat_target::detach (inferior *inf, int from_tty)
   gdb_assert (num_lwps (pid) == 1
 	      || (target_is_non_stop_p () && num_lwps (pid) == 0));
 
-  if (pid == inferior_ptid.pid () && forks_exist_p ())
+  if (forks_exist_p (inf))
     {
       /* Multi-fork case.  The current inferior_ptid is being detached
 	 from, but there are other viable forks to debug.  Detach from
 	 the current fork, and context-switch to the first
 	 available.  */
-      linux_fork_detach (from_tty, find_lwp_pid (ptid_t (pid)));
+      linux_fork_detach (from_tty, find_lwp_pid (ptid_t (pid)), inf);
     }
   else
     {
@@ -2082,8 +2082,12 @@  linux_handle_extended_wait (struct lwp_info *lp, int status)
 	  detach_breakpoints (ptid_t (new_pid, new_pid));
 
 	  /* Retain child fork in ptrace (stopped) state.  */
-	  if (!find_fork_pid (new_pid))
-	    add_fork (new_pid);
+	  if (find_fork_pid (new_pid).first == nullptr)
+	    {
+	      struct inferior *inf = find_inferior_ptid (linux_target,
+	                                                 lp->ptid);
+	      add_fork (new_pid, inf);
+	    }
 
 	  /* Report as spurious, so that infrun doesn't want to follow
 	     this fork.  We're actually doing an infcall in
@@ -3729,8 +3733,8 @@  linux_nat_target::kill ()
      parent will be sleeping if this is a vfork.  */
   iterate_over_lwps (pid_ptid, kill_unfollowed_child_callback);
 
-  if (forks_exist_p ())
-    linux_fork_killall ();
+  if (forks_exist_p (current_inferior ()))
+    linux_fork_killall (current_inferior ());
   else
     {
       /* Stop all threads before killing them, since ptrace requires
@@ -3761,7 +3765,7 @@  linux_nat_target::mourn_inferior ()
 
   close_proc_mem_file (pid);
 
-  if (! forks_exist_p ())
+  if (! forks_exist_p (current_inferior ()))
     /* Normal case, no other forks available.  */
     inf_ptrace_target::mourn_inferior ();
   else
diff --git a/gdb/testsuite/gdb.base/checkpoint.exp b/gdb/testsuite/gdb.base/checkpoint.exp
index 31b5a13bb8f..4a8a9a8eb7f 100644
--- a/gdb/testsuite/gdb.base/checkpoint.exp
+++ b/gdb/testsuite/gdb.base/checkpoint.exp
@@ -274,17 +274,17 @@  gdb_test "kill" "" "kill all one" \
 # and confirm that all are gone
 #
 
-gdb_test "restart 0" "Not found.*" "no more checkpoint 0"
-gdb_test "restart 1" "Not found.*" "no more checkpoint 1"
-gdb_test "restart 2" "Not found.*" "no more checkpoint 2"
-gdb_test "restart 3" "Not found.*" "no more checkpoint 3"
-gdb_test "restart 4" "Not found.*" "no more checkpoint 4"
-gdb_test "restart 5" "Not found.*" "no more checkpoint 5"
-gdb_test "restart 6" "Not found.*" "no more checkpoint 6"
-gdb_test "restart 7" "Not found.*" "no more checkpoint 7"
-gdb_test "restart 8" "Not found.*" "no more checkpoint 8"
-gdb_test "restart 9" "Not found.*" "no more checkpoint 9"
-gdb_test "restart 10" "Not found.*" "no more checkpoint 10"
+gdb_test "restart 0" "has no checkpoints" "no more checkpoint 0"
+gdb_test "restart 1" "has no checkpoints" "no more checkpoint 1"
+gdb_test "restart 2" "has no checkpoints" "no more checkpoint 2"
+gdb_test "restart 3" "has no checkpoints" "no more checkpoint 3"
+gdb_test "restart 4" "has no checkpoints" "no more checkpoint 4"
+gdb_test "restart 5" "has no checkpoints" "no more checkpoint 5"
+gdb_test "restart 6" "has no checkpoints" "no more checkpoint 6"
+gdb_test "restart 7" "has no checkpoints" "no more checkpoint 7"
+gdb_test "restart 8" "has no checkpoints" "no more checkpoint 8"
+gdb_test "restart 9" "has no checkpoints" "no more checkpoint 9"
+gdb_test "restart 10" "has no checkpoints" "no more checkpoint 10"
 
 #
 # Now let's try setting a large number of checkpoints (>600)
@@ -331,7 +331,7 @@  gdb_assert { $nr_ok == 600 } "break1 with many checkpoints"
 set count 0
 set msg "info checkpoints with at least 600 checkpoints"
 gdb_test_multiple "info checkpoints" $msg {
-    -re "\r\n  $decimal process \[^\r\]*" {
+    -re "\r\n *$decimal n +process \[^\r\]*" {
 	incr count
 	exp_continue
     }
diff --git a/gdb/testsuite/gdb.multi/checkpoint-multi.exp b/gdb/testsuite/gdb.multi/checkpoint-multi.exp
new file mode 100644
index 00000000000..2bd654347b0
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/checkpoint-multi.exp
@@ -0,0 +1,800 @@ 
+# Copyright 2009-2024 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This file tests various scenarios involving multiple inferiors
+# and the checkpoint command.
+
+# Checkpoint support works only on Linux.
+require {istarget "*-*-linux*"}
+
+# Checkpoint support is implemented for the (Linux) native target.
+require gdb_protocol_is_native
+
+set checkpoints_header_re " +Id +Active Target Id +Frame.*?"
+set proc_re "(?:process $::decimal|Thread $::hex \\(LWP $::decimal\\))"
+set ckpt_re "checkpoint"
+set main_proc "\\(main process\\)"
+set hello_c "hello\\.c"
+set goodbye_c "goodbye\\.c"
+set hangout_c "hangout\\.c"
+
+set testfile "checkpoint-multi"
+
+set exec1 "hello"
+set srcfile1 ${exec1}.c
+set binfile1 [standard_output_file ${exec1}]
+
+set exec2 "goodbye"
+set srcfile2 ${exec2}.c
+set binfile2 [standard_output_file ${exec2}]
+
+set exec3 "hangout"
+set srcfile3 ${exec3}.c
+set binfile3 [standard_output_file ${exec3}]
+
+if { [build_executable ${testfile}.exp ${exec1} "${srcfile1}" {debug}] == -1 } {
+    return -1
+}
+
+if { [build_executable ${testfile}.exp ${exec2} "${srcfile2}" {debug}] == -1 } {
+    return -1
+}
+
+if { [build_executable ${testfile}.exp ${exec3} "${srcfile3}" {debug}] == -1 } {
+    return -1
+}
+
+# Start two inferiors, place a checkpoint on inferior 2, but switch
+# back to inferior 1.
+proc start_2_inferiors_checkpoint_on_inf_2 {} {
+    clean_restart $::exec1
+
+    # Start inferior 1.
+    if {[gdb_start_cmd] < 0} {
+	fail "start first inferior"
+    } else {
+	gdb_test "" "main.*" "start first inferior"
+    }
+
+    # Add a new inferior and exec into it.
+    gdb_test "add-inferior -exec $::binfile2" \
+	"Added inferior 2.*" \
+	"add inferior 2 with -exec $::exec2"
+
+    # Check that we have multiple inferiors.
+    gdb_test "info inferiors" \
+	"Executable.*$::exec1.*$::exec2.*"
+
+    # Switch to inferior 2.
+    gdb_test "inferior 2" \
+	"Switching to inferior 2.*$::exec2.*"
+
+    # Start inferior 2:
+    if {[gdb_start_cmd] < 0} {
+	fail "start second inferior"
+    } else {
+	gdb_test "" "main.*" "start second inferior"
+    }
+
+    # Set a checkpoint in inferior 2
+    gdb_test "checkpoint" "$::ckpt_re 2\\.1: fork returned pid $::decimal.*"
+
+    # Step one line in inferior 2.
+    gdb_test "step" "glob = 46;"
+
+    # Switch back to inferior 1.
+    gdb_test "inferior 1" "Switching to inferior 1.*$::exec1.*"
+}
+
+# Start two inferiors, place a checkpoint on inferior 2, but switch
+# back to inferior 1.  This is like the one above, except that it
+# swaps the executables loaded into inferior 1 and inferior 2.  This
+# is important for being able to test "continue to exit".  (Because...
+# hello.c has an infinite loop, but goodbye.c doesn't.  In order to
+# test "continue to exit", we need to continue in an executable which
+# will actually exit.)
+
+proc start_2_inferiors_checkpoint_on_inf_2_alt {} {
+    clean_restart $::exec2
+
+    # Start inferior 1.
+    if {[gdb_start_cmd] < 0} {
+	fail "start first inferior"
+    } else {
+	gdb_test "" "main.*" "start first inferior"
+    }
+
+    # Add a new inferior and exec exec1 into it.
+    gdb_test "add-inferior -exec $::binfile1" \
+	"Added inferior 2.*" \
+	"add inferior 2 with -exec $::exec1"
+
+    # Check that we have two inferiors.
+    gdb_test "info inferiors" \
+	"Executable.*$::exec2.*$::exec1.*"
+
+    # Switch to inferior 2.
+    gdb_test "inferior 2" \
+	"Switching to inferior 2.*$::exec1.*"
+
+    # Start inferior 2:
+    if {[gdb_start_cmd] < 0} {
+	fail "start second inferior"
+    } else {
+	gdb_test "" "main.*" "start second inferior"
+    }
+
+    # Set a checkpoint in inferior 2
+    gdb_test "checkpoint" "$::ckpt_re 2\\.1: fork returned pid $::decimal.*"
+
+    # next one line in inferior 2.
+    gdb_test "next" "bar\\(\\).*"
+
+    # Switch back to inferior 1.
+    gdb_test "inferior 1" "Switching to inferior 1.*$::exec2.*"
+}
+
+with_test_prefix "check detach on non-checkpointed inferior" {
+    start_2_inferiors_checkpoint_on_inf_2
+    gdb_test "detach" "Detaching from program.*$::exec1.*Inferior 1.*detached.*"
+}
+
+with_test_prefix "check kill on non-checkpointed inferior" {
+    start_2_inferiors_checkpoint_on_inf_2
+    gdb_test "kill" "" "kill non-checkpointed inferior" \
+	     "Kill the program being debugged.*y or n. $" "y"
+}
+
+with_test_prefix "check restart 0 on non-checkpointed inferior" {
+    start_2_inferiors_checkpoint_on_inf_2
+    gdb_test "restart 0" "Inferior 1 has no checkpoints"
+    gdb_test "restart 2.0" "Switching to inferior 2.*?goodbye.*?#0 +mailand .*?glob = 46;.*"
+}
+
+with_test_prefix "check restart 1 on non-checkpointed inferior" {
+    start_2_inferiors_checkpoint_on_inf_2
+    gdb_test "restart 1" "Inferior 1 has no checkpoints"
+    gdb_test "restart 2.1" "Switching to inferior 2.*?goodbye.*?#0 +main .*?mailand\\(\\);.*"
+}
+
+with_test_prefix "check continue to exit on non-checkpointed inferior" {
+    start_2_inferiors_checkpoint_on_inf_2_alt
+    gdb_test "continue" "Inferior 1.*? exited normally.*"
+}
+
+with_test_prefix "two inferiors with checkpoints" {
+    start_2_inferiors_checkpoint_on_inf_2
+    with_test_prefix "one checkpoint" {
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		" +2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		" +2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+    with_test_prefix "two checkpoints" {
+	gdb_test "checkpoint" "$ckpt_re 1\\.1: fork returned pid $::decimal.*" \
+		 "checkpoint in inferior 1"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"\\* 1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    # Note: No switching is done here since checkpoint 0 is the active one.
+    gdb_test "restart 0" "main.*?$hello_c.*?alarm \\(240\\);"
+
+    gdb_test "restart 2.0" \
+	     "\\\[Switching to inferior 2.*?mailand.*?glob = 46;.*"
+    gdb_test "next" "\}"
+
+    with_test_prefix "restart 1" {
+	gdb_test "restart 1" "^Switching to $proc_re.*?#0  main \\(\\) at.*?$goodbye_c.*mailand\\(\\);"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "info checkpoints twice in a row" {
+	# Doing "info_checkpoints" twice in a row might seem pointless,
+	# but during work on making the checkpoint code inferior aware,
+	# there was a point at which doing it twice in a row did not
+	# produce the same output.
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "restart 0" {
+	# Switch back to checkpoint 0; again, there should be no
+	# "Switching to inferior" message.
+	gdb_test "restart 0" \
+		 "^Switching to $proc_re.*?#0  mailand \\(\\) at.*?$goodbye_c.*\}"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"\\* 2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    # Try switching to invalid checkpoints:
+    with_test_prefix "invalid checkpoints" {
+	gdb_test "restart 3" "Invalid checkpoint number 3 for inferior 2"
+	gdb_test "restart 2" "Invalid checkpoint number 2 for inferior 2"
+	gdb_test "restart -1" "Checkpoint number must be a non-negative integer"
+	gdb_test "restart 2.3" "Invalid checkpoint number 3 for inferior 2"
+	gdb_test "restart 3.0" "No inferior number '3'"
+	gdb_test "restart 1.2" "Invalid checkpoint number 2 for inferior 1"
+	gdb_test "restart 1.3" "Invalid checkpoint number 3 for inferior 1"
+	gdb_test "restart 1.-1" "Checkpoint number must be a non-negative integer"
+	gdb_test "restart -1.0" "Inferior number must be a positive integer"
+    }
+
+    with_test_prefix "restart 1.1" {
+	# Switch to checkpoint 1.1; this time, we should see a "Switching to
+	# inferior" message.
+	gdb_test "restart 1.1" \
+		 "\\\[Switching to inferior 1.*?main.*?$hello_c.*?alarm \\(240\\);"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"\\* 1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "restart 2.1" {
+	gdb_test "restart 2.1" \
+		 "Switching to inferior 2.*?#0  main \\(\\) at.*?$goodbye_c.*mailand\\(\\);"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "second checkpoint in inferior 2" {
+	gdb_test "checkpoint" "$ckpt_re 2\\.2: fork returned pid $::decimal.*"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "third checkpoint in inferior 2" {
+	gdb_test "checkpoint" "$ckpt_re 2.3: fork returned pid $::decimal.*"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.3 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "continue to exit in checkpoint 2.1" {
+	gdb_test "continue" \
+		 "Inferior 2 \\(process $decimal\\) exited normally.*?Switching to $proc_re.*?"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.3 y +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "continue to exit in checkpoint 2.3" {
+	gdb_test "continue" \
+		 "Inferior 2 \\(process $decimal\\) exited normally.*?Switching to process $decimal.*?"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "continue to exit in checkpoint 2.2" {
+	gdb_test "continue" \
+		 "Inferior 2 \\(process $decimal\\) exited normally.*?Switching to process $decimal.*?"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?"]
+    }
+
+    with_test_prefix "new checkpoints in inferior 2" {
+	gdb_test "checkpoint" "$ckpt_re 2.1: fork returned pid $::decimal.*" \
+		 "checkpoint 2.1"
+
+	gdb_test "checkpoint" "$ckpt_re 2.2: fork returned pid $::decimal.*" \
+		 "checkpoint 2.2"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"\\* 2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "delete checkpoint 2.0" {
+	gdb_test "delete checkpoint 2.0" \
+		 "Cannot delete active checkpoint" \
+		 "failed attempt to delete active checkpoint 2.0"
+
+	gdb_test "restart 2.1" \
+		 "^Switching to process.*?#0  mailand \\(\\) at.*?$goodbye_c.*\}"
+
+	gdb_test "delete checkpoint 2.0" \
+		 "Killed process $::decimal"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "delete checkpoint 2.2" {
+	gdb_test "delete checkpoint 2.2" \
+		 "Killed process $::decimal"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?"]
+    }
+
+    with_test_prefix "new checkpoint in inferior 2" {
+	gdb_test "checkpoint" "$ckpt_re 2.1: fork returned pid $::decimal.*"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"\\* 2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "switch to inferior 1" {
+	gdb_test "inferior 1" "Switching to inferior 1.*?alarm \\(240\\);"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"\\* 1\\.1 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "kill inferior 1" {
+	gdb_test "kill" "\\\[Inferior 1 \\(process $::decimal\\) killed\\\]" \
+		 "kill inferior 1" \
+		 "Kill the program being debugged.*y or n. $" "y"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "start inferior 1 again" {
+	gdb_test "checkpoint" "The program is not being run\\." \
+		 "checkpoint in non-running inferior"
+
+	gdb_test "start" "Starting program.*?hello.*?alarm \\(240\\);"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "checkpoint 1.1" {
+	gdb_test "checkpoint" "$ckpt_re 1.1: fork returned pid $::decimal.*" \
+		 "second checkpoint in inferior 1"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"\\* 1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+}
+
+with_test_prefix "three inferiors with checkpoints" {
+    start_2_inferiors_checkpoint_on_inf_2
+
+    gdb_test "info checkpoints" \
+	[multi_line \
+	    "$checkpoints_header_re" \
+	    "  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+	    "  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+
+    with_test_prefix "add third inferior" {
+	# Add a third inferior and exec into it.
+	gdb_test "add-inferior -exec $::binfile3" \
+		 "Added inferior 3.*" \
+		 "add inferior 3 with -exec $::exec3"
+
+	# Check that we have three inferiors.
+	gdb_test "info inferiors" \
+		 "Executable.*?\\* 1 .*?$::exec1.*? 2 .*?$::exec2.*? 3 .*?$::exec3.*?" \
+		 "check for three inferiors"
+
+	# Switch to inferior 3.
+	gdb_test "inferior 3" \
+	    "Switching to inferior 3.*$::exec3.*"
+
+	# Start inferior 2:
+	if {[gdb_start_cmd] < 0} {
+	    fail "start third inferior"
+	} else {
+	    gdb_test "" "main.*" "start third inferior"
+	}
+
+	gdb_test "checkpoint" "$ckpt_re 3\\.1: fork returned pid $::decimal.*"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.1 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "make checkpoint in inferior 1" {
+	gdb_test "inferior 1" "Switching to inferior 1.*?alarm \\(240\\);"
+
+	gdb_test "checkpoint" "$ckpt_re 1\\.1: fork returned pid $::decimal.*"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"\\* 1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.1 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "restart 2.1" {
+	gdb_test "restart 2.1" \
+		 "Switching to inferior 2.*?#0  main \\(\\) at.*?$goodbye_c.*mailand\\(\\);"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.1 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "next and make new checkpoint" {
+	gdb_test "next" "foo\\(glob\\);"
+	gdb_test "checkpoint" "$ckpt_re 2\\.2: fork returned pid $::decimal.*"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.1 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "switch to inferior 3 for upcoming kill" {
+	gdb_test "inferior 3" "Switching to inferior 3.*?alarm \\(30\\);"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.1 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "kill inferior 3" {
+	gdb_test "kill" "\\\[Inferior 3 \\(process $::decimal\\) killed\\\]" \
+		 "kill inferior 3" \
+		 "Kill the program being debugged.*y or n. $" "y"
+
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" ]
+    }
+
+    with_test_prefix "delete checkpoint 2.0" {
+	gdb_test "delete checkpoint 0" \
+		 "Inferior 3 has no checkpoints"
+	gdb_test "delete checkpoint 2.0" \
+		 "Killed process $::decimal"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" ]
+    }
+
+    with_test_prefix "restart 2.2" {
+	gdb_test "restart 2.2" \
+		 "Switching to inferior 2.*?#0  main \\(\\) at.*?$goodbye_c.*foo\\(glob\\);"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" ]
+    }
+
+    with_test_prefix "switch to non-running inferior 3" {
+	gdb_test "inferior 3" "\\\[Switching to inferior 3 \\\[<null>\\\] \\(.*?$::exec3\\)\\\]"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" ]
+    }
+
+    with_test_prefix "restart inferior 3 and make new checkpoints" {
+	gdb_test "start" "Starting program.*?hangout.*?alarm \\(30\\);"
+	gdb_test "checkpoint" \
+		 "$ckpt_re 3\\.1: fork returned pid $::decimal.*" \
+		 "checkpoint 3.1"
+	gdb_test "checkpoint" \
+		 "$ckpt_re 3\\.2: fork returned pid $::decimal.*" \
+		 "checkpoint 3.2"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.1 n +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.2 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "delete checkpoint 3.1" {
+	gdb_test "delete checkpoint 1" \
+		 "Killed process $::decimal"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.2 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "attempt to delete active checkpoint in non-current inferior" {
+	# Switch to inferior 1, add another checkpoint - so that there
+	# are three of them in inferior 1 - then switch back to
+	# inferior 3 and delete active checkpoint in inferior 1.
+	# Then, switch to inferior 1 and attempt to add another
+	# checkpoint.  During development, a "Cannot access memory at
+	# address ..." message was seen.  This was a bug - there were
+	# several problems - but one of them was that the checkpoint in
+	# question was an "active" checkpoint.  The fix was to
+	# disallow this case.
+	gdb_test "inferior 1" "Switching to inferior 1.*?alarm \\(240\\);"
+	gdb_test "checkpoint" "$ckpt_re 1\\.2: fork returned pid $::decimal.*"
+	gdb_test "inferior 3" "Switching to inferior 3.*?alarm \\(30\\);"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.2 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.2 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+
+	# Check that deleting active checkpoints in other (non-current)
+	# inferiors is disallowed.
+	gdb_test "delete checkpoint 1.0" \
+		 "Cannot delete active checkpoint"
+    }
+
+    with_test_prefix "delete non-active checkpoint in non-current inferior" {
+	# But deleting non-active checkpoints, even in other inferiors,
+	# should work.
+	gdb_test "delete checkpoint 1.1" \
+		 "Killed process $::decimal"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.2 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.2 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "switch to inferior 1" {
+	gdb_test "inferior 1" "Switching to inferior 1.*?alarm \\(240\\);"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"\\* 1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.2 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.2 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "checkpoint 1.3" {
+	gdb_test "checkpoint" "$ckpt_re 1\\.3: fork returned pid $::decimal.*" \
+		 "third checkpoint in inferior 1"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"\\* 1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.2 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.3 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.2 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  3\\.0 y +$proc_re +at $::hex, file.*?$hangout_c.*?" \
+		"  3\\.2 n +$proc_re +at $::hex, file.*?$hangout_c.*?"]
+    }
+
+    with_test_prefix "attempt to remove active but not current inferior" {
+	gdb_test "x/i \$pc" "=> $::hex <main.*"
+	gdb_test "remove-inferior 3" \
+		 "warning: Can not remove active inferior 3\."
+    }
+}
+
+with_test_prefix "background execution" {
+    start_2_inferiors_checkpoint_on_inf_2
+    with_test_prefix "one checkpoint" {
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  2.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+    with_test_prefix "two checkpoints" {
+	gdb_test "checkpoint" "$ckpt_re 1\\.1: fork returned pid $::decimal.*" \
+		 "checkpoint in inferior 1"
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"\\* 1\\.0 y +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "background continue hello" {
+	gdb_test "continue &" "Continuing\."
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"\\* 1\\.0 y +$proc_re \\(running\\)" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "fail to switch to inferior 2 w/ 1 in background" {
+	gdb_test "restart 2.1" "Cannot execute this command while the selected thread is running."
+	# Should be no change from earlier output.
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"\\* 1\\.0 y +$proc_re \\(running\\)" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+
+    with_test_prefix "switch to inferior 2" {
+	set msg "stop thread"
+	gdb_test_multiple "interrupt" $msg {
+	    -re "$gdb_prompt " {
+		gdb_test_multiple "" $msg {
+		    -re "Thread 1\\.1 \"hello\" received signal SIGINT, Interrupt\\." {
+			pass $gdb_test_name
+		    }
+		}
+	    }
+	}
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"\\* 1\\.0 y +$proc_re +at $::hex,.*" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 y +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"  2\\.1 n +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+	gdb_test "restart 2.1" "Switching to inferior 2.*?goodbye.*?#0 +main .*?mailand\\(\\);.*"
+    }
+
+    with_test_prefix "after restart 2.1" {
+	gdb_test "info checkpoints" \
+	    [multi_line \
+		"$checkpoints_header_re" \
+		"  1\\.0 y +$proc_re +at $::hex,.*" \
+		"  1\\.1 n +$proc_re +at $::hex, file.*?$hello_c.*?" \
+		"  2\\.0 n +$proc_re +at $::hex, file.*?$goodbye_c.*?" \
+		"\\* 2\\.1 y +$proc_re +at $::hex, file.*?$goodbye_c.*?"]
+    }
+}