From: Yao Qi <qiyaoltc@gmail.com>
To: Pedro Alves <palves@redhat.com>
Cc: gdb-patches@sourceware.org
Subject: Re: [PATCH 3/7] Force to insert software single step breakpoint
Date: Wed, 13 Apr 2016 16:21:00 -0000 [thread overview]
Message-ID: <86d1pto4xe.fsf@gmail.com> (raw)
In-Reply-To: <570BB52F.7@redhat.com>
Pedro Alves <palves@redhat.com> writes:
> Another scenario occurred to me:
>
> - Thread A is software single-stepping.
> - Thread B hits single-step breakpoint of thread A.
> - We pause all threads and set thread B stepping past the
> single-step breakpoint of thread A.
>
> But if the single-step breakpoint is for another thread, then
> we won't actually manage to have thread B step past it, resulting
> in spurious re-hits and no-guaranteed forward progress. See
> e.g., non-stop-fair-events.exp:
>
> # On software single-step targets that don't support displaced
> # stepping, threads keep hitting each others' single-step
> # breakpoints, and then GDB needs to pause all threads to step
> # past those. The end result is that progress in the main
> # thread will be slower and it may take a bit longer for the
> # signal to be queued; bump the timeout.
I finally managed to reproduce that thread id in step_over_info is
different from the thread id of the single-step breakpoint.
GDB now gives the high priority to finishing step over, to avoid
"threads keep hitting each others' single-step breakpoint". With my
patch applied, single-step breakpoint (of threads other than we are
stepping over) is still inserted even we try to step past the location,
so the step-over can't be finished.
>
> Sounds like we may need to look at the single-step breakpoint's thread
> id, and only insert it if it is for the thread that is going to be
> doing the step-over? We may need to record that in step_over_info and
> pass more info to stepping_past_instruction_at.
Yes, after I added a new field 'struct thread_info *thread' in
'struct step_over_info', I realize that IWBN to convert 'step_over_info'
to 'the thread we are stepping over', so the fields 'aspace' and 'address'
can be replaced by 'thread', like this,
struct step_over_info
{
struct thread_info *thread;
int nonsteppable_watchpoint_p;
};
Is it a good idea? If there is nothing obviously wrong, I'll post
patches to do this.
--
Yao (齐尧)
next prev parent reply other threads:[~2016-04-13 16:21 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-23 16:10 [PATCH 0/7 V2] Step over instruction branches to itself Yao Qi
2016-03-23 16:10 ` [PATCH 5/7] [GDBserver] Don't error in reinsert_raw_breakpoint if bp->inserted Yao Qi
2016-04-11 14:54 ` Pedro Alves
2016-03-23 16:10 ` [PATCH 1/7] New test case gdb.trace/signal.exp Yao Qi
2016-04-08 16:52 ` Pedro Alves
2016-04-11 8:41 ` Yao Qi
2016-04-11 14:04 ` Pedro Alves
2016-04-22 10:53 ` Yao Qi
2016-04-26 12:57 ` Pedro Alves
2016-04-11 14:08 ` Pedro Alves
2016-03-23 16:10 ` [PATCH 3/7] Force to insert software single step breakpoint Yao Qi
2016-04-11 14:31 ` Pedro Alves
2016-04-13 16:21 ` Yao Qi [this message]
2016-04-19 14:54 ` Yao Qi
2016-04-19 15:17 ` Pedro Alves
2016-04-20 7:50 ` Yao Qi
2016-04-22 16:36 ` Pedro Alves
2016-04-25 8:40 ` Yao Qi
2016-03-23 16:10 ` [PATCH 6/7] Resume the inferior with signal rather than stepping over Yao Qi
2016-04-11 15:29 ` Pedro Alves
2016-03-23 16:10 ` [PATCH 4/7] Insert breakpoint even when the raw breakpoint is found Yao Qi
2016-04-11 14:41 ` Pedro Alves
2016-04-12 9:04 ` Yao Qi
2016-04-12 9:41 ` Pedro Alves
2016-04-25 8:45 ` Yao Qi
2016-03-23 16:10 ` [PATCH 2/7] Deliver signal in hardware single step Yao Qi
2016-04-11 14:10 ` Pedro Alves
2016-04-22 10:54 ` Yao Qi
2016-03-23 16:26 ` [PATCH 7/7] New test case gdb.base/branch-to-self.exp Yao Qi
2016-04-11 15:34 ` Pedro Alves
2016-04-25 8:58 ` Yao Qi
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