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From: Ingo Molnar <mingo@kernel.org>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Ingo Molnar <mingo@redhat.com>, Jiri Olsa <jolsa@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Alexander Potapenko <glider@google.com>,
	Al Viro <viro@zeniv.linux.org.uk>, Arnd Bergmann <arnd@arndb.de>,
	Christian Brauner <christian@brauner.io>,
	Jann Horn <jannh@google.com>, Jens Axboe <axboe@kernel.dk>,
	Matt Morehouse <mascasa@google.com>,
	Peter Collingbourne <pcc@google.com>,
	Ian Rogers <irogers@google.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH v3 07/11] perf: Add breakpoint information to siginfo on SIGTRAP
Date: Thu, 25 Mar 2021 15:18:20 +0100	[thread overview]
Message-ID: <20210325141820.GA1456211@gmail.com> (raw)
In-Reply-To: <CACT4Y+aKmdsXhRZi2f3LsX3m=krdY4kPsEUcieSugO2wY=xA-Q@mail.gmail.com>


* Dmitry Vyukov <dvyukov@google.com> wrote:

> On Wed, Mar 24, 2021 at 3:05 PM Marco Elver <elver@google.com> wrote:
> >
> > On Wed, 24 Mar 2021 at 15:01, Peter Zijlstra <peterz@infradead.org> wrote:
> > >
> > > One last try, I'll leave it alone now, I promise :-)
> >
> > This looks like it does what you suggested, thanks! :-)
> >
> > I'll still need to think about it, because of the potential problem
> > with modify-signal-races and what the user's synchronization story
> > would look like then.
> 
> I agree that this looks inherently racy. The attr can't be allocated
> on stack, user synchronization may be tricky and expensive. The API
> may provoke bugs and some users may not even realize the race problem.

Yeah, so why cannot we allocate enough space from the signal handler 
user-space stack and put the attr there, and point to it from 
sig_info?

The idea would be to create a stable, per-signal snapshot of whatever 
the perf_attr state is at the moment the event happens and the signal 
is generated - which is roughly what user-space wants, right?

Thanks,

	Ingo

  parent reply	other threads:[~2021-03-25 14:19 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-24 11:24 [PATCH v3 00/11] Add support for synchronous signals on perf events Marco Elver
2021-03-24 11:24 ` [PATCH v3 01/11] perf: Rework perf_event_exit_event() Marco Elver
2021-03-25 10:17   ` Marco Elver
2021-03-25 16:17     ` Marco Elver
2021-03-25 19:10       ` Marco Elver
2021-03-29 11:50         ` Peter Zijlstra
2021-03-24 11:24 ` [PATCH v3 02/11] perf: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES to children Marco Elver
2021-03-24 11:24 ` [PATCH v3 03/11] perf: Support only inheriting events if cloned with CLONE_THREAD Marco Elver
2021-03-24 11:24 ` [PATCH v3 04/11] perf: Add support for event removal on exec Marco Elver
2021-03-24 11:24 ` [PATCH v3 05/11] signal: Introduce TRAP_PERF si_code and si_perf to siginfo Marco Elver
2021-03-24 11:24 ` [PATCH v3 06/11] perf: Add support for SIGTRAP on perf events Marco Elver
2021-03-25  8:14   ` Marco Elver
2021-03-29 12:07     ` Peter Zijlstra
2021-03-29 14:27       ` Oleg Nesterov
2021-03-29 14:32         ` Marco Elver
2021-03-30  7:04           ` Peter Zijlstra
2021-03-29 18:22         ` Marco Elver
2021-03-29 18:33           ` Oleg Nesterov
2021-03-31 12:32       ` Marco Elver
2021-03-31 14:51         ` Peter Zijlstra
2021-03-31 16:50           ` Marco Elver
2021-03-24 11:24 ` [PATCH v3 07/11] perf: Add breakpoint information to siginfo on SIGTRAP Marco Elver
2021-03-24 12:53   ` Peter Zijlstra
2021-03-24 13:01     ` Peter Zijlstra
2021-03-24 13:21       ` Peter Zijlstra
2021-03-24 13:43         ` Peter Zijlstra
2021-03-24 14:00           ` Peter Zijlstra
2021-03-24 14:05             ` Marco Elver
2021-03-24 14:12               ` Dmitry Vyukov
2021-03-24 14:15                 ` Dmitry Vyukov
2021-03-25  7:00                   ` Marco Elver
2021-03-25 14:18                 ` Ingo Molnar [this message]
2021-03-25 15:17                   ` Marco Elver
2021-03-25 15:35                     ` Ingo Molnar
2021-03-24 13:47         ` Marco Elver
2021-03-24 11:25 ` [PATCH v3 08/11] selftests/perf_events: Add kselftest for process-wide sigtrap handling Marco Elver
2021-03-24 11:25 ` [PATCH v3 09/11] selftests/perf_events: Add kselftest for remove_on_exec Marco Elver
2021-03-24 11:25 ` [PATCH v3 10/11] tools headers uapi: Sync tools/include/uapi/linux/perf_event.h Marco Elver
2021-03-24 11:25 ` [PATCH v3 11/11] perf test: Add basic stress test for sigtrap handling Marco Elver

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