[02/31] linux-nat: introduce pending_status_str

  I noticed that some debug log output printing an lwp's pending status
wasn't considering lp->waitstatus.  This fixes it, by introducing a
new pending_status_str function.

Change-Id: I66e5c7a363d30a925b093b195d72925ce5b6b980
---
 gdb/linux-nat.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)
  

Pedro Alves <pedro@palves.net> writes:

> I noticed that some debug log output printing an lwp's pending status
> wasn't considering lp->waitstatus.  This fixes it, by introducing a
> new pending_status_str function.

This patch looks fine.  I had one slightly related question:  I took a
look at the comment on lwp_info::waitstatus in linux-nat.h, which says:

  /* If WAITSTATUS->KIND != TARGET_WAITKIND_SPURIOUS, the waitstatus
     for this LWP's last event.  This may correspond to STATUS above,
     or to a local variable in lin_lwp_wait.  */
  struct target_waitstatus waitstatus;

Am I right in thinking that this comment is wrong; it should say
TARGET_WAITKIND_IGNORE, not TARGET_WAITKIND_SPURIOUS, right?

Thanks,
Andrew


>
> Change-Id: I66e5c7a363d30a925b093b195d72925ce5b6b980
> ---
>  gdb/linux-nat.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
> index 17e5dce08c3..9b78fd1f8e8 100644
> --- a/gdb/linux-nat.c
> +++ b/gdb/linux-nat.c
> @@ -256,6 +256,19 @@ is_leader (lwp_info *lp)
>    return lp->ptid.pid () == lp->ptid.lwp ();
>  }
>  
> +/* Convert an LWP's pending status to a std::string.  */
> +
> +static std::string
> +pending_status_str (lwp_info *lp)
> +{
> +  gdb_assert (lwp_status_pending_p (lp));
> +
> +  if (lp->waitstatus.kind () != TARGET_WAITKIND_IGNORE)
> +    return lp->waitstatus.to_string ();
> +  else
> +    return status_to_str (lp->status);
> +}
> +
>  
>  /* LWP accessors.  */
>  
> @@ -1647,8 +1660,8 @@ linux_nat_target::resume (ptid_t scope_ptid, int step, enum gdb_signal signo)
>  	 this thread with a signal?  */
>        gdb_assert (signo == GDB_SIGNAL_0);
>  
> -      linux_nat_debug_printf ("Short circuiting for status 0x%x",
> -			      lp->status);
> +      linux_nat_debug_printf ("Short circuiting for status %s",
> +			      pending_status_str (lp).c_str ());
>  
>        if (target_can_async_p ())
>  	{
> @@ -3137,7 +3150,7 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
>    if (lp != NULL)
>      {
>        linux_nat_debug_printf ("Using pending wait status %s for %s.",
> -			      status_to_str (lp->status).c_str (),
> +			      pending_status_str (lp).c_str (),
>  			      lp->ptid.to_string ().c_str ());
>      }
>  
> -- 
> 2.36.0
  

On 2023-02-03 12:00 p.m., Andrew Burgess wrote:
> Pedro Alves <pedro@palves.net> writes:
> 
>> I noticed that some debug log output printing an lwp's pending status
>> wasn't considering lp->waitstatus.  This fixes it, by introducing a
>> new pending_status_str function.
> 
> This patch looks fine.  I had one slightly related question:  I took a
> look at the comment on lwp_info::waitstatus in linux-nat.h, which says:
> 
>   /* If WAITSTATUS->KIND != TARGET_WAITKIND_SPURIOUS, the waitstatus
>      for this LWP's last event.  This may correspond to STATUS above,
>      or to a local variable in lin_lwp_wait.  */
>   struct target_waitstatus waitstatus;
> 
> Am I right in thinking that this comment is wrong; it should say
> TARGET_WAITKIND_IGNORE, not TARGET_WAITKIND_SPURIOUS, right?

You're right.

I tweaked the comments in linux-nat.h in this new version.  Let me know what
you think.

From 10f88baff2e25fb87f37d1665bf283206171dd42 Mon Sep 17 00:00:00 2001
From: Pedro Alves <pedro@palves.net>
Date: Fri, 12 Nov 2021 20:50:29 +0000
Subject: [PATCH] linux-nat: introduce pending_status_str

I noticed that some debug log output printing an lwp's pending status
wasn't considering lp->waitstatus.  This fixes it, by introducing a
new pending_status_str function.

Also fix the comment in gdb/linux-nat.h describing
lwp_info::waitstatus and details the description of lwp_info::status
while at it.

Change-Id: I66e5c7a363d30a925b093b195d72925ce5b6b980
---
 gdb/linux-nat.c | 19 ++++++++++++++++---
 gdb/linux-nat.h | 11 +++++++----
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index e5391b9ce35..9d811bbf3ff 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -255,6 +255,19 @@ is_leader (lwp_info *lp)
   return lp->ptid.pid () == lp->ptid.lwp ();
 }
 
+/* Convert an LWP's pending status to a std::string.  */
+
+static std::string
+pending_status_str (lwp_info *lp)
+{
+  gdb_assert (lwp_status_pending_p (lp));
+
+  if (lp->waitstatus.kind () != TARGET_WAITKIND_IGNORE)
+    return lp->waitstatus.to_string ();
+  else
+    return status_to_str (lp->status);
+}
+
 
 /* LWP accessors.  */
 
@@ -1647,8 +1660,8 @@ linux_nat_target::resume (ptid_t scope_ptid, int step, enum gdb_signal signo)
 	 this thread with a signal?  */
       gdb_assert (signo == GDB_SIGNAL_0);
 
-      linux_nat_debug_printf ("Short circuiting for status 0x%x",
-			      lp->status);
+      linux_nat_debug_printf ("Short circuiting for status %s",
+			      pending_status_str (lp).c_str ());
 
       if (target_can_async_p ())
 	{
@@ -3137,7 +3150,7 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
   if (lp != NULL)
     {
       linux_nat_debug_printf ("Using pending wait status %s for %s.",
-			      status_to_str (lp->status).c_str (),
+			      pending_status_str (lp).c_str (),
 			      lp->ptid.to_string ().c_str ());
     }
 
diff --git a/gdb/linux-nat.h b/gdb/linux-nat.h
index 45534c92386..770fe924427 100644
--- a/gdb/linux-nat.h
+++ b/gdb/linux-nat.h
@@ -232,7 +232,9 @@ struct lwp_info : intrusive_list_node<lwp_info>
   /* The last resume GDB requested on this thread.  */
   resume_kind last_resume_kind = resume_continue;
 
-  /* If non-zero, a pending wait status.  */
+  /* If non-zero, a pending wait status.  A pending process exit is
+     recorded in WAITSTATUS, because W_EXITCODE(0,0) happens to be
+     0.  */
   int status = 0;
 
   /* When 'stopped' is set, this is where the lwp last stopped, with
@@ -260,9 +262,10 @@ struct lwp_info : intrusive_list_node<lwp_info>
   /* Non-zero if we expect a duplicated SIGINT.  */
   int ignore_sigint = 0;
 
-  /* If WAITSTATUS->KIND != TARGET_WAITKIND_SPURIOUS, the waitstatus
-     for this LWP's last event.  This may correspond to STATUS above,
-     or to a local variable in lin_lwp_wait.  */
+  /* If WAITSTATUS->KIND != TARGET_WAITKIND_IGNORE, the waitstatus for
+     this LWP's last event.  This usually corresponds to STATUS above,
+     however because W_EXITCODE(0,0) happens to be 0, a process exit
+     will be recorded here, while 'status == 0' is ambiguous.  */
   struct target_waitstatus waitstatus;
 
   /* Signal whether we are in a SYSCALL_ENTRY or

base-commit: 2562954ede66f32bff7d985e752b8052c2ae5775
prerequisite-patch-id: bbc9918ac5f79de07a29f34ec072794d270f942d
  

Pedro Alves <pedro@palves.net> writes:

> On 2023-02-03 12:00 p.m., Andrew Burgess wrote:
>> Pedro Alves <pedro@palves.net> writes:
>> 
>>> I noticed that some debug log output printing an lwp's pending status
>>> wasn't considering lp->waitstatus.  This fixes it, by introducing a
>>> new pending_status_str function.
>> 
>> This patch looks fine.  I had one slightly related question:  I took a
>> look at the comment on lwp_info::waitstatus in linux-nat.h, which says:
>> 
>>   /* If WAITSTATUS->KIND != TARGET_WAITKIND_SPURIOUS, the waitstatus
>>      for this LWP's last event.  This may correspond to STATUS above,
>>      or to a local variable in lin_lwp_wait.  */
>>   struct target_waitstatus waitstatus;
>> 
>> Am I right in thinking that this comment is wrong; it should say
>> TARGET_WAITKIND_IGNORE, not TARGET_WAITKIND_SPURIOUS, right?
>
> You're right.
>
> I tweaked the comments in linux-nat.h in this new version.  Let me know what
> you think.
>
> From 10f88baff2e25fb87f37d1665bf283206171dd42 Mon Sep 17 00:00:00 2001
> From: Pedro Alves <pedro@palves.net>
> Date: Fri, 12 Nov 2021 20:50:29 +0000
> Subject: [PATCH] linux-nat: introduce pending_status_str
>
> I noticed that some debug log output printing an lwp's pending status
> wasn't considering lp->waitstatus.  This fixes it, by introducing a
> new pending_status_str function.
>
> Also fix the comment in gdb/linux-nat.h describing
> lwp_info::waitstatus and details the description of lwp_info::status
> while at it.
>
> Change-Id: I66e5c7a363d30a925b093b195d72925ce5b6b980
> ---
>  gdb/linux-nat.c | 19 ++++++++++++++++---
>  gdb/linux-nat.h | 11 +++++++----
>  2 files changed, 23 insertions(+), 7 deletions(-)

LGTM.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>
> diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
> index e5391b9ce35..9d811bbf3ff 100644
> --- a/gdb/linux-nat.c
> +++ b/gdb/linux-nat.c
> @@ -255,6 +255,19 @@ is_leader (lwp_info *lp)
>    return lp->ptid.pid () == lp->ptid.lwp ();
>  }
>  
> +/* Convert an LWP's pending status to a std::string.  */
> +
> +static std::string
> +pending_status_str (lwp_info *lp)
> +{
> +  gdb_assert (lwp_status_pending_p (lp));
> +
> +  if (lp->waitstatus.kind () != TARGET_WAITKIND_IGNORE)
> +    return lp->waitstatus.to_string ();
> +  else
> +    return status_to_str (lp->status);
> +}
> +
>  
>  /* LWP accessors.  */
>  
> @@ -1647,8 +1660,8 @@ linux_nat_target::resume (ptid_t scope_ptid, int step, enum gdb_signal signo)
>  	 this thread with a signal?  */
>        gdb_assert (signo == GDB_SIGNAL_0);
>  
> -      linux_nat_debug_printf ("Short circuiting for status 0x%x",
> -			      lp->status);
> +      linux_nat_debug_printf ("Short circuiting for status %s",
> +			      pending_status_str (lp).c_str ());
>  
>        if (target_can_async_p ())
>  	{
> @@ -3137,7 +3150,7 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
>    if (lp != NULL)
>      {
>        linux_nat_debug_printf ("Using pending wait status %s for %s.",
> -			      status_to_str (lp->status).c_str (),
> +			      pending_status_str (lp).c_str (),
>  			      lp->ptid.to_string ().c_str ());
>      }
>  
> diff --git a/gdb/linux-nat.h b/gdb/linux-nat.h
> index 45534c92386..770fe924427 100644
> --- a/gdb/linux-nat.h
> +++ b/gdb/linux-nat.h
> @@ -232,7 +232,9 @@ struct lwp_info : intrusive_list_node<lwp_info>
>    /* The last resume GDB requested on this thread.  */
>    resume_kind last_resume_kind = resume_continue;
>  
> -  /* If non-zero, a pending wait status.  */
> +  /* If non-zero, a pending wait status.  A pending process exit is
> +     recorded in WAITSTATUS, because W_EXITCODE(0,0) happens to be
> +     0.  */
>    int status = 0;
>  
>    /* When 'stopped' is set, this is where the lwp last stopped, with
> @@ -260,9 +262,10 @@ struct lwp_info : intrusive_list_node<lwp_info>
>    /* Non-zero if we expect a duplicated SIGINT.  */
>    int ignore_sigint = 0;
>  
> -  /* If WAITSTATUS->KIND != TARGET_WAITKIND_SPURIOUS, the waitstatus
> -     for this LWP's last event.  This may correspond to STATUS above,
> -     or to a local variable in lin_lwp_wait.  */
> +  /* If WAITSTATUS->KIND != TARGET_WAITKIND_IGNORE, the waitstatus for
> +     this LWP's last event.  This usually corresponds to STATUS above,
> +     however because W_EXITCODE(0,0) happens to be 0, a process exit
> +     will be recorded here, while 'status == 0' is ambiguous.  */
>    struct target_waitstatus waitstatus;
>  
>    /* Signal whether we are in a SYSCALL_ENTRY or
>
> base-commit: 2562954ede66f32bff7d985e752b8052c2ae5775
> prerequisite-patch-id: bbc9918ac5f79de07a29f34ec072794d270f942d
> -- 
> 2.36.0
  

On 2023-03-16 4:19 p.m., Andrew Burgess wrote:
> Pedro Alves <pedro@palves.net> writes:

>> I tweaked the comments in linux-nat.h in this new version.  Let me know what
>> you think.
>>
>> From 10f88baff2e25fb87f37d1665bf283206171dd42 Mon Sep 17 00:00:00 2001
>> From: Pedro Alves <pedro@palves.net>
>> Date: Fri, 12 Nov 2021 20:50:29 +0000
>> Subject: [PATCH] linux-nat: introduce pending_status_str
>>
>> I noticed that some debug log output printing an lwp's pending status
>> wasn't considering lp->waitstatus.  This fixes it, by introducing a
>> new pending_status_str function.
>>
>> Also fix the comment in gdb/linux-nat.h describing
>> lwp_info::waitstatus and details the description of lwp_info::status
>> while at it.
>>
>> Change-Id: I66e5c7a363d30a925b093b195d72925ce5b6b980
>> ---
>>  gdb/linux-nat.c | 19 ++++++++++++++++---
>>  gdb/linux-nat.h | 11 +++++++----
>>  2 files changed, 23 insertions(+), 7 deletions(-)
> 
> LGTM.
> 
> Reviewed-By: Andrew Burgess <aburgess@redhat.com>
> 

Thanks, I've merged this one as well, as it's pretty much independent/standalone.