linux-kernel - Re: [PATCH v4 02/39] task_work: Fix TWA_NMI_CURRENT race with _

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Message-ID: <20250123081522.GB3808@noisy.programming.kicks-ass.net>
Date: Thu, 23 Jan 2025 09:15:22 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, Indu Bhagat <indu.bhagat@...cle.com>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	linux-toolchains@...r.kernel.org, Jordan Rome <jordalgo@...a.com>,
	Sam James <sam@...too.org>, linux-trace-kernel@...r.kernel.org,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Jens Remus <jremus@...ux.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Florian Weimer <fweimer@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Weinan Liu <wnliu@...gle.com>
Subject: Re: [PATCH v4 02/39] task_work: Fix TWA_NMI_CURRENT race with
 __schedule()

On Wed, Jan 22, 2025 at 02:14:30PM -0800, Josh Poimboeuf wrote:
> On Wed, Jan 22, 2025 at 01:03:42PM -0800, Josh Poimboeuf wrote:
> > The self-IPI is only needed when the NMI happened in user space, right?
> > Would it make sense to have an optimized version of that?
> 
> Actually, maybe not, that could be tricky if the NMI hits in the kernel
> after task work runs.

Right, I was going to say, lets keep this as simple as possible :-)