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[PING]Re: [PATCH v2 3/3] PR remote/19496, timeout in forking-threads-plus-bkpt
- From: Don Breazeal <donb at codesourcery dot com>
- To: <gdb-patches at sourceware dot org>, <palves at redhat dot com>
- Date: Thu, 25 Feb 2016 09:29:33 -0800
- Subject: [PING]Re: [PATCH v2 3/3] PR remote/19496, timeout in forking-threads-plus-bkpt
- Authentication-results: sourceware.org; auth=none
- References: <1455150506-12760-1-git-send-email-donb at codesourcery dot com>
Ping
Thanks,
--Don
On 2/10/2016 4:28 PM, Don Breazeal wrote:
> On 2/1/2016 12:09 PM, Pedro Alves wrote:
>> On 02/01/2016 07:29 PM, Don Breazeal wrote:
>>> On 2/1/2016 4:05 AM, Pedro Alves wrote:
>>
>>> Hi Pedro,
> ---snip---
>>> A fork event was reported to GDB before GDB knew about the parent thread,
>>> followed immediately by a breakpoint event in a different thread. The
>>> parent thread was subsequently added via remote_notice_new_inferior in
>>> process_stop_reply, but when the thread was added the thread_info.state
>>> was set to THREAD_STOPPED. The fork event was then handled correctly,
>>> but when the fork parent was resumed via a call to keep_going, the state
>>> was unchanged.
>>
>> Since this is non-stop, then it sounds to me like the bug is that the
>> thread should have been added in THREAD_RUNNING state.
>>
>> Consider that infrun may be pulling target events out of the target_ops
>> backend into its own event queue, but, not process them immediately.
>>
>> E.g., infrun may be stopping all threads temporarily for a step-over-breakpoint
>> operation for thread A (stop_all_threads). The waitstatus of all threads
>> is thus left pending in the thread structure (save_status), including the
>> fork event of thread B. Right at this point, if the user
>> does "info threads", that should show thread B (the fork parent) running,
>> not stopped, even if internally, gdb is holding it paused for a little bit.
>>
>
> Hi Pedro,
> Here is a new patch that adds the threads with the state set to
> THREAD_RUNNING for fork events.
> Thanks!
> --Don
>
> This patch addresses a failure in
> gdb.threads/forking-threads-plus-breakpoint.exp:
>
> FAIL: gdb.threads/forking-threads-plus-breakpoint.exp: cond_bp_target=1:
> detach_on_fork=on: inferior 1 exited (timeout)
>
> Cause:
> A fork event was reported to GDB before GDB knew about the parent thread,
> followed immediately by a breakpoint event in a different thread. The
> parent thread was subsequently added via remote_notice_new_inferior in
> process_stop_reply, but when the thread was added the thread_info.state
> was set to THREAD_STOPPED. The fork event was then handled correctly,
> but when the fork parent was resumed via a call to keep_going, the state
> was unchanged.
>
> The breakpoint event was then handled, which caused all the non-breakpoint
> threads to be stopped. When the breakpoint thread was resumed, all the
> non-breakpoint threads were resumed via infrun.c:restart_threads. Our old
> fork parent wasn't restarted, because it still had thread_info.state set to
> THREAD_STOPPED. Ultimately the program under debug hung waiting for a
> pthread_join while the old fork parent was stopped forever by GDB.
>
> Fix:
> Make sure to add the fork parent thread in the THREAD_RUNNING state by
> calling remote_notice_new_inferior with RUNNING set to 1 when processing
> a fork stop reply.
>
> Tested on x86_64 Linux and Nios II Linux target with x86 Linux host.
>
> gdb/ChangeLog:
> 2016-02-10 Don Breazeal <donb@codesourcery.com>
>
> * remote.c (process_stop_reply): Call remote_notice_new_inferior
> with RUNNING set to 1 when handling fork events.
>
> ---
> gdb/remote.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/remote.c b/gdb/remote.c
> index f09a06e..ab750a7 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -6818,7 +6818,14 @@ process_stop_reply (struct stop_reply *stop_reply,
> VEC_free (cached_reg_t, stop_reply->regcache);
> }
>
> - remote_notice_new_inferior (ptid, 0);
> + /* If a fork event arrived before we knew about the parent thread,
> + make sure to mark it as running when it is created. */
> + if (status->kind == TARGET_WAITKIND_FORKED
> + || status->kind == TARGET_WAITKIND_VFORKED)
> + remote_notice_new_inferior (ptid, 1);
> + else
> + remote_notice_new_inferior (ptid, 0);
> +
> remote_thr = demand_private_info (ptid);
> remote_thr->core = stop_reply->core;
> remote_thr->stop_reason = stop_reply->stop_reason;
>