diff mbox

linux_nat.c: Mark new thread running even if momentarily pausing

Message ID 1427376746-31596-1-git-send-email-palves@redhat.com
State New, archived
Headers

Commit Message

Pedro Alves March 26, 2015, 1:32 p.m. UTC 
  My all-stop-on-top-of-non-stop series manages to trip on a bug in the
linux-nat.c backend while running the testsuite.  If a thread is
discovered while threads are being momentarily paused (without the
core's intervention), the thread ends up stuck in THREAD_STOPPED
state, even though from the user's perspective, the thread is running
even while it is paused.

From inspection, in the current sources, this can happen if we call
stop_and_resume_callback, though there's no way to test that with
current Linux kernels.

(While trying to come up with test to exercise this, I stumbled on:
  https://sourceware.org/ml/gdb-patches/2015-03/msg00850.html

... which does include a non-trivial test, so I think I can still
claim I come out net positive. :-) )

Tested on x86_64 Fedora 20.

gdb/ChangeLog:
2015-03-26  Pedro Alves  <palves@redhat.com>

	* linux-nat.c (linux_handle_extended_wait): Always call set_running.
---
 gdb/linux-nat.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Pedro Alves April 1, 2015, 1:26 p.m. UTC | #1 
On 03/26/2015 01:32 PM, Pedro Alves wrote:
> My all-stop-on-top-of-non-stop series manages to trip on a bug in the
> linux-nat.c backend while running the testsuite.  If a thread is
> discovered while threads are being momentarily paused (without the
> core's intervention), the thread ends up stuck in THREAD_STOPPED
> state, even though from the user's perspective, the thread is running
> even while it is paused.
> 
> From inspection, in the current sources, this can happen if we call
> stop_and_resume_callback, though there's no way to test that with
> current Linux kernels.
> 
> (While trying to come up with test to exercise this, I stumbled on:
>   https://sourceware.org/ml/gdb-patches/2015-03/msg00850.html
> 
> ... which does include a non-trivial test, so I think I can still
> claim I come out net positive. :-) )
> 
> Tested on x86_64 Fedora 20.
> 
> gdb/ChangeLog:
> 2015-03-26  Pedro Alves  <palves@redhat.com>
> 
> 	* linux-nat.c (linux_handle_extended_wait): Always call set_running.

Pushed.

Thanks,
Pedro Alves
diff mbox

Patch

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 0376299..04707dc 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -2109,9 +2109,12 @@  linux_handle_extended_wait (struct lwp_info *lp, int status,
 	      add_thread (new_lp->ptid);
 	    }
 
+	  /* Even if we're stopping the thread for some reason
+	     internal to this module, from the user/frontend's
+	     perspective, this new thread is running.  */
+	  set_running (new_lp->ptid, 1);
 	  if (!stopping)
 	    {
-	      set_running (new_lp->ptid, 1);
 	      set_executing (new_lp->ptid, 1);
 	      /* thread_db_attach_lwp -> lin_lwp_attach_lwp forced
 		 resume_stop.  */