linux-kernel - Re: [PATCH v3 2/4] perf: Enqueue SIGTRAP always via task

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Message-ID: <20240410144821.bVdBdVOR@linutronix.de>
Date: Wed, 10 Apr 2024 16:48:21 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Frederic Weisbecker <frederic@...nel.org>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>, Ingo Molnar <mingo@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>, Marco Elver <elver@...gle.com>,
	Mark Rutland <mark.rutland@....com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH v3 2/4] perf: Enqueue SIGTRAP always via task_work.

On 2024-04-10 16:42:56 [+0200], Frederic Weisbecker wrote:
> > > Like this then?
> > > 
> > > https://lore.kernel.org/all/202403310406.TPrIela8-lkp@intel.com/T/#m63c28147d8ac06b21c64d7784d49f892e06c0e50
> > 
> > Kind of, yes. Do we have more than one waiter? If not, maybe that
> > rcuwait would work then.
> 
> Indeed there is only one waiter so that should work. Would
> that be something you can call while preemption is disabled?

rcuwait_wake_up() does only wake_up_process() which is fine.
wake_up() does spin_lock_irqsave() which is a no.

On the other hand that preempt-disable needs to go anyway due to
perf_sigtrap(). But a slim wake is a slim wake ;)

> Thanks.

Sebastian