From: Pedro Alves <palves@redhat.com>
To: Yao Qi <qiyaoltc@gmail.com>
Cc: gdb-patches@sourceware.org
Subject: Re: [PATCH 11/12] Use reinsert_breakpoint for vCont;s
Date: Tue, 14 Jun 2016 15:48:00 -0000 [thread overview]
Message-ID: <1cec772e-a659-3f2f-1eae-67d27fdbd9e0@redhat.com> (raw)
In-Reply-To: <86h9cvud2z.fsf@gmail.com>
On 06/14/2016 02:14 PM, Yao Qi wrote:
> Pedro Alves <palves@redhat.com> writes:
>
>>> @@ -4293,7 +4313,7 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp,
>>>
>>> step = maybe_hw_step (thread);
>>> }
>>> - else
>>> + else if (lwp->resume != NULL && lwp->resume->kind != resume_step)
>>> {
>>> /* If the thread isn't doing step-over, there shouldn't be any
>>> reinsert breakpoints. */
>>
>> Consider (non-stop RSP):
>>
>> -> vCont;s:1
>> <- OK
>> -> vCont;s:2
>> <- OK
>>
>> The handling of the second vCont sets thread 1's lwp->resume to NULL.
>
> If so, the assert won't be called for thread 1.
>
>> The lwp->resume pointer is only meaningful within linux_resume
>> and its callees. (But this function is called in other contexts.)
>>
>
> When I wrote the patch, it took me a while to think about this condition
> check. I wanted to remove this condition and assert, but finally
> decided to leave it there, as it is not harmful. If lwp->resume is only
> meaningful within linux_resume and its callees, how about remove the
> condition check and assert here?
Yes, if it's only for the assert, then let's remove it.
>
>>> @@ -5009,12 +5033,52 @@ linux_resume (struct thread_resume *resume_info, size_t n)
>>> debug_printf ("Resuming, no pending status or step over needed\n");
>>> }
>>>
>>> + /* Before we resume the threads, if resume_step is requested by GDB,
>>> + stop all threads and install reinsert breakpoints. */
>>
>> Looking again, I think the rationale for stopping threads should
>> be mentioned here, as it's not obvious.
>>
>
> How about this,
>
> /* Before we resume the threads, if resume_step is requested by GDB,
> we need to access the inferior memory to install reinsert
> breakpoints, so stop all threads. */
That doesn't tell the reader why we need to stop _all_ threads. The
threads that are about to be resumed are obviously stopped, and
thus we could already _access_ inferior memory through them.
I guess this is about flushing instruction caches?
>>> @@ -5176,6 +5241,30 @@ proceed_all_lwps (void)
>>> if (debug_threads)
>>> debug_printf ("Proceeding, no step-over needed\n");
>>>
>>> + /* Re-install the reinsert breakpoints on software single step target
>>> + if the client wants it step. */
>>> + if (can_software_single_step ())
>>
>> Not immediately obvious to why is this necessary. Where were they
>> removed in the first place? I'm it must be necessary, but maybe
>> extending the comment helps.
>
> How about this
>
> /* On software single step target, we removed reinsert breakpoints
> after we get any events from the inferior.
Is that all events, even internal events? From the patch, it seemed
like it was only before reporting an event to gdb.
> If the client wants
> thread step, re-install these reinsert breakpoints. */
>
If we only remove before reporting an event to gdb, then I don't
understand this. We already insert single-step breakpoints when
we process the resume request from gdb, no?
Thanks,
Pedro Alves
next prev parent reply other threads:[~2016-06-14 15:48 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-02 9:31 [PATCH 00/12 V2] Use reinsert breakpoint " Yao Qi
2016-06-02 9:31 ` [PATCH 04/12] Delete reinsert breakpoints from forked child Yao Qi
2016-06-13 15:02 ` Pedro Alves
2016-06-13 16:53 ` Yao Qi
2016-06-13 17:29 ` Pedro Alves
2016-06-14 11:17 ` Yao Qi
2016-06-14 11:40 ` Pedro Alves
2016-06-17 9:53 ` Yao Qi
2016-06-02 9:31 ` [PATCH 08/12] Refactor clone_all_breakpoints Yao Qi
2016-06-13 15:14 ` Pedro Alves
2016-06-02 9:31 ` [PATCH 09/12] Make reinsert_breakpoint thread specific Yao Qi
2016-06-13 15:24 ` Pedro Alves
2016-06-14 12:52 ` Yao Qi
2016-06-14 12:57 ` Pedro Alves
2016-06-02 9:31 ` [PATCH 10/12] Switch current_thread to lwp's thread in install_software_single_step_breakpoints Yao Qi
2016-06-13 15:26 ` Pedro Alves
2016-06-02 9:31 ` [PATCH 05/12] Handle reinsert breakpoints for vforked child Yao Qi
2016-06-13 15:07 ` Pedro Alves
2016-06-02 9:31 ` [PATCH 11/12] Use reinsert_breakpoint for vCont;s Yao Qi
2016-06-13 15:55 ` Pedro Alves
2016-06-14 13:14 ` Yao Qi
2016-06-14 15:48 ` Pedro Alves [this message]
2016-06-15 16:41 ` Yao Qi
2016-06-17 15:10 ` Pedro Alves
2016-06-20 18:09 ` Antoine Tremblay
2016-06-02 9:31 ` [PATCH 12/12] Support vCont s and S actions with software single step Yao Qi
2016-06-13 15:56 ` Pedro Alves
2016-06-02 9:31 ` [PATCH 07/12] Create sub classes of 'struct breakpoint' Yao Qi
2016-06-13 15:09 ` Pedro Alves
2016-06-02 9:31 ` [PATCH 01/12] Switch to current thread in finish_step_over Yao Qi
2016-06-13 14:25 ` Pedro Alves
2016-06-02 9:31 ` [PATCH 03/12] Step over exit with reinsert breakpoints Yao Qi
2016-06-13 14:37 ` Pedro Alves
2016-06-13 14:52 ` Yao Qi
2016-06-13 15:01 ` Pedro Alves
2016-06-17 9:50 ` Yao Qi
2016-06-02 9:31 ` [PATCH 02/12] More assert checks on reinsert breakpoint Yao Qi
2016-06-13 14:25 ` Pedro Alves
2016-06-02 9:31 ` [PATCH 06/12] Pass breakpoint type in set_breakpoint_at Yao Qi
2016-06-13 15:07 ` Pedro Alves
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