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Re: Inadvertently run inferior threads
- From: Eli Zaretskii <eliz at gnu dot org>
- To: Pedro Alves <palves at redhat dot com>
- Cc: gdb at sourceware dot org
- Date: Wed, 10 Jun 2015 18:15:10 +0300
- Subject: Re: Inadvertently run inferior threads
- Authentication-results: sourceware.org; auth=none
- References: <83h9tq3zu3 dot fsf at gnu dot org> <55043A63 dot 6020103 at redhat dot com> <8361a339xd dot fsf at gnu dot org> <5504555C dot 804 at redhat dot com> <550458E0 dot 10206 at redhat dot com> <55045AB9 dot 2000408 at redhat dot com>
- Reply-to: Eli Zaretskii <eliz at gnu dot org>
> Date: Sat, 14 Mar 2015 15:58:49 +0000
> From: Pedro Alves <palves@redhat.com>
> CC: gdb@sourceware.org
>
> On 03/14/2015 03:50 PM, Pedro Alves wrote:
>
> >> Calling a function that ends up starting new threads should
> >> work OK, but indeed that seems to be broken...
> >>
> >> On GNU/Linux, and a trivial program with:
> >>
> >> ~~~
> >> void
> >> start_thread (void)
> >> {
> >> pthread_t thread;
> >>
> >> pthread_create (&thread, NULL, thread_function, NULL);
> >> }
> >> ~~~
> >>
> >> results in:
> >>
> >> (gdb) p start_thread ()
> >> [New Thread 0x7ffff7fc1700 (LWP 9903)]
> >> $1 = void
> >> (gdb) info threads
> >> Id Target Id Frame
> >> 2 Thread 0x7ffff7fc1700 (LWP 9903) "start-thread-in" (running)
> >> * 1 Thread 0x7ffff7fc2740 (LWP 9899) "start-thread-in" main () at start-thread-infcall.c:35
> >>
> >
> > I see what's going on here:
> >
> > #1 - we suppress the *stopped -> *running transitions/notification when
> > doing an inferior function call (the in_infcall checks in infrun.c).
> >
> > #2 - new threads are spawned and given *running state, because well,
> > they're running.
> >
> > #3 - we suppress the running -> *stopped transition when doing
> > an infcall, like in #1. (The in_infcall check in normal_stop).
> >
> > #4 - result: _new_ threads end up in "running" state, even though they
> > are stopped.
> >
> > I don't know off hand what the best fix is.
>
> This is now: https://sourceware.org/bugzilla/show_bug.cgi?id=18127
I think I'm starting to understand why this happens. I will describe
my findings in the bug report.