From: Peter Zijlstra <peterz@infradead.org>
To: Marco Elver <elver@google.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
kasan-dev@googlegroups.com, Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH] perf: Fix missing SIGTRAPs due to pending_disable abuse
Date: Tue, 4 Oct 2022 19:21:45 +0200 [thread overview]
Message-ID: <YzxrqUFBNy/kR6PZ@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <Yzxou9HB/1XjMXWI@hirez.programming.kicks-ass.net>
On Tue, Oct 04, 2022 at 07:09:15PM +0200, Peter Zijlstra wrote:
> On Wed, Sep 28, 2022 at 04:55:46PM +0200, Marco Elver wrote:
> > On Wed, Sep 28, 2022 at 12:06PM +0200, Marco Elver wrote:
> >
> > > My second idea about introducing something like irq_work_raw_sync().
> > > Maybe it's not that crazy if it is actually safe. I expect this case
> > > where we need the irq_work_raw_sync() to be very very rare.
> >
> > The previous irq_work_raw_sync() forgot about irq_work_queue_on(). Alas,
> > I might still be missing something obvious, because "it's never that
> > easy". ;-)
> >
> > And for completeness, the full perf patch of what it would look like
> > together with irq_work_raw_sync() (consider it v1.5). It's already
> > survived some shorter stress tests and fuzzing.
>
> So.... I don't like it. But I cooked up the below, which _almost_ works :-/
>
> For some raisin it sometimes fails with 14999 out of 15000 events
> delivered and I've not yet figured out where it goes sideways. I'm
> currently thinking it's that sigtrap clear on OFF.
Oh Urgh, this is ofcourse the case where an IPI races with a migration
and we loose the race with return to use. Effectively giving the signal
skid vs the hardware event.
Bah.. I really hate having one CPU wait for another... Let me see if I
can find another way to close that hole.
next prev parent reply other threads:[~2022-10-04 17:22 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-27 12:13 [PATCH] perf: Fix missing SIGTRAPs due to pending_disable abuse Marco Elver
2022-09-27 12:30 ` Marco Elver
2022-09-27 18:20 ` Peter Zijlstra
2022-09-27 21:45 ` Marco Elver
2022-09-28 10:06 ` Marco Elver
2022-09-28 14:55 ` Marco Elver
2022-10-04 17:09 ` Peter Zijlstra
2022-10-04 17:21 ` Peter Zijlstra [this message]
2022-10-04 17:33 ` Marco Elver
2022-10-05 7:37 ` Peter Zijlstra
2022-10-05 7:49 ` Marco Elver
2022-10-05 8:23 ` Peter Zijlstra
2022-10-06 13:33 ` [PATCH] perf: Fix missing SIGTRAPs Peter Zijlstra
2022-10-06 13:59 ` Marco Elver
2022-10-06 16:02 ` Peter Zijlstra
2022-10-07 9:37 ` Marco Elver
2022-10-07 13:09 ` Peter Zijlstra
2022-10-07 13:58 ` Marco Elver
2022-10-07 16:14 ` Marco Elver
2022-10-08 8:41 ` Marco Elver
2022-10-08 12:41 ` Peter Zijlstra
2022-10-10 20:52 ` Marco Elver
2022-10-08 13:51 ` Peter Zijlstra
2022-10-08 14:08 ` Peter Zijlstra
2022-10-11 7:44 ` [PATCH v2] " Peter Zijlstra
2022-10-11 12:58 ` Marco Elver
2022-10-11 13:06 ` Peter Zijlstra
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