From: Pedro Alves <palves@redhat.com>
To: "Metzger, Markus T" <markus.t.metzger@intel.com>
Cc: "jan.kratochvil@redhat.com" <jan.kratochvil@redhat.com>,
"gdb-patches@sourceware.org" <gdb-patches@sourceware.org>,
Eli Zaretskii <eliz@gnu.org>
Subject: Re: [patch v8 24/24] record-btrace: add (reverse-)stepping support
Date: Tue, 17 Dec 2013 20:07:00 -0000 [thread overview]
Message-ID: <52B0AEEE.7030803@redhat.com> (raw)
In-Reply-To: <A78C989F6D9628469189715575E55B230AA39796@IRSMSX104.ger.corp.intel.com>
On 12/17/2013 02:14 PM, Metzger, Markus T wrote:
> Does scheduler locking set inferior_ptid?
> If it does, we should already get the desired behaviour.
It does, but only by chance. The thread to resume will
be in ptid passed to target_resume. But I confirm
the code already does the right thing.
>
>
>>>>> + /* Find the thread to move. */
>>>>> + if (ptid_equal (minus_one_ptid, ptid) || ptid_is_pid (ptid))
>>>>> + {
>>>>> + ALL_THREADS (tp)
>>>>> + record_btrace_resume_thread (tp, flag);
>>>>
>>>> Seems like this steps all threads, when gdb only wants to
>>>> step inferior_ptid and continue others?
>>>
>>> Only if gdb passes -1 or the ptid of the process.
>>
>> Yes, but -1 or "ptid of the process" means "step inferior_ptid
>> and let others run free".
>
> See below.
>
>
>>> In the end, we will move exactly one thread and keep all
>>> others where they are. This one thread will hit a breakpoint
>>> or run out of execution history.
>>
>> Some of the other threads can hit a breakpoint before the
>> current thread hits one too.
>
> That depends on thread interleaving. There is no guarantee that
> the other threads make progress. The way it is currently
> implemented, we step the chosen thread until the next event.
> This event is either a breakpoint, step completed, or out of
> execution history.
>
> We're effectively only stepping a single thread. I believe this
> is also how the s/w record target works.
I'd understand that if the code looked obviously like but,
how the quoted code above seems to be resuming/stepping all
threads?
/* Find the thread to move. */
if (ptid_equal (minus_one_ptid, ptid) || ptid_is_pid (ptid))
{
ALL_THREADS (tp)
record_btrace_resume_thread (tp, flag);
> But this means that I would rely on inferior_ptid in to_resume
> if -1 or the process id is passed.
That's fine. target_resume is telling the target "resume _this_",
albeit getting what "this" is has a weird interface. It's
target_wait that's the problem. The user can have e.g., thread 3
selected (meaning inferior_ptid points at thread 3), while
target_wait returns an event for some other thread. There's
really no connection here.
--
Pedro Alves
next prev parent reply other threads:[~2013-12-17 20:07 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-12 9:15 [patch v8 00/24] record-btrace: reverse Markus Metzger
2013-12-12 9:15 ` [patch v8 03/24] gdbarch: add instruction predicate methods Markus Metzger
2013-12-12 9:15 ` [patch v8 01/24] btrace, linux: fix memory leak when reading branch trace Markus Metzger
2013-12-12 9:15 ` [patch v8 14/24] record-btrace: supply register target methods Markus Metzger
2013-12-12 9:15 ` [patch v8 16/24] record-btrace, frame: supply target-specific unwinder Markus Metzger
2013-12-12 9:16 ` [patch v8 24/24] record-btrace: add (reverse-)stepping support Markus Metzger
2013-12-12 16:36 ` Eli Zaretskii
2013-12-13 19:22 ` Pedro Alves
2013-12-16 15:56 ` Metzger, Markus T
2013-12-16 20:30 ` Pedro Alves
2013-12-17 14:14 ` Metzger, Markus T
2013-12-17 15:07 ` Metzger, Markus T
2013-12-17 15:48 ` Metzger, Markus T
2013-12-17 20:41 ` Pedro Alves
2013-12-17 20:34 ` Pedro Alves
2013-12-17 20:07 ` Pedro Alves [this message]
2013-12-18 9:44 ` Metzger, Markus T
2013-12-12 9:16 ` [patch v8 13/24] target: add ops parameter to to_prepare_to_store method Markus Metzger
2013-12-12 9:16 ` [patch v8 15/24] frame, backtrace: allow targets to supply a frame unwinder Markus Metzger
2013-12-13 18:27 ` Pedro Alves
2013-12-16 9:18 ` Metzger, Markus T
2013-12-16 19:02 ` Pedro Alves
2013-12-17 8:26 ` Metzger, Markus T
2013-12-17 9:48 ` Pedro Alves
2013-12-12 9:16 ` [patch v8 18/24] record-btrace: add to_wait and to_resume target methods Markus Metzger
2013-12-12 9:16 ` [patch v8 06/24] btrace: change branch trace data structure Markus Metzger
2013-12-12 9:16 ` [patch v8 08/24] record-btrace: start counting at one Markus Metzger
2013-12-12 9:16 ` [patch v8 02/24] btrace: uppercase btrace_read_type Markus Metzger
2013-12-12 9:16 ` [patch v8 09/24] btrace: increase buffer size Markus Metzger
2013-12-12 9:16 ` [patch v8 10/24] record-btrace: optionally indent function call history Markus Metzger
2013-12-12 9:16 ` [patch v8 21/24] record-btrace: extend unwinder Markus Metzger
2013-12-13 19:45 ` Pedro Alves
2013-12-16 12:42 ` Metzger, Markus T
2013-12-16 19:22 ` Pedro Alves
2013-12-17 12:56 ` Metzger, Markus T
2013-12-12 9:16 ` [patch v8 12/24] btrace: add replay position to btrace thread info Markus Metzger
2013-12-12 9:16 ` [patch v8 20/24] record-btrace: add record goto target methods Markus Metzger
2013-12-12 9:16 ` [patch v8 04/24] frame: add frame_is_tailcall function Markus Metzger
2013-12-12 9:16 ` [patch v8 11/24] record-btrace: make ranges include begin and end Markus Metzger
2013-12-13 17:56 ` Pedro Alves
2013-12-12 9:16 ` [patch v8 05/24] frame: artificial frame id's Markus Metzger
2013-12-12 19:39 ` Pedro Alves
2013-12-12 19:55 ` Jan Kratochvil
2013-12-13 8:04 ` Metzger, Markus T
2013-12-13 11:27 ` Jan Kratochvil
2013-12-13 11:42 ` Metzger, Markus T
2013-12-13 12:09 ` Pedro Alves
2013-12-13 13:01 ` Metzger, Markus T
2013-12-13 15:44 ` Pedro Alves
2013-12-13 17:51 ` Pedro Alves
2013-12-18 13:30 ` Metzger, Markus T
2013-12-12 9:16 ` [patch v8 23/24] record-btrace: show trace from enable location Markus Metzger
2013-12-13 19:50 ` Pedro Alves
2013-12-16 12:57 ` Metzger, Markus T
2013-12-16 19:41 ` Pedro Alves
2013-12-17 13:20 ` Metzger, Markus T
2013-12-17 16:59 ` Pedro Alves
2013-12-12 9:16 ` [patch v8 07/24] record-btrace: fix insn range in function call history Markus Metzger
2013-12-12 9:16 ` [patch v8 19/24] record-btrace: provide target_find_new_threads method Markus Metzger
2013-12-12 9:16 ` [patch v8 17/24] record-btrace: provide xfer_partial target method Markus Metzger
2013-12-13 18:43 ` Pedro Alves
2013-12-16 10:53 ` Metzger, Markus T
2013-12-16 19:16 ` Pedro Alves
2013-12-17 11:58 ` Metzger, Markus T
2013-12-17 16:56 ` Pedro Alves
2013-12-18 9:26 ` Metzger, Markus T
2013-12-18 10:39 ` Pedro Alves
2013-12-12 9:16 ` [patch v8 22/24] btrace, gdbserver: read branch trace incrementally Markus Metzger
2013-12-13 19:46 ` Pedro Alves
2013-12-16 12:47 ` Metzger, Markus T
2013-12-16 19:23 ` Pedro Alves
2013-12-12 14:07 ` [patch v8 00/24] record-btrace: reverse Jan Kratochvil
2013-12-12 14:19 ` Metzger, Markus T
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