linux-kernel - Re: [PATCH RFC 1/3] arm64/gcs: Support reuse of GCS for exited threads

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Message-ID: <13c4ada9-bc32-46cc-a7b4-3def7a4e94fb@sirena.org.uk>
Date: Fri, 26 Sep 2025 12:37:44 +0100
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>, Christian Brauner <brauner@...nel.org>,
	Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>,
	Shuah Khan <shuah@...nel.org>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Deepak Gupta <debug@...osinc.com>,
	Wilco Dijkstra <wilco.dijkstra@....com>,
	Carlos O'Donell <codonell@...hat.com>,
	Florian Weimer <fweimer@...hat.com>, Szabolcs Nagy <nsz@...t70.net>,
	Rich Felker <dalias@...c.org>, libc-alpha@...rceware.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH RFC 1/3] arm64/gcs: Support reuse of GCS for exited
 threads

On Fri, Sep 26, 2025 at 12:14:21PM +0100, Catalin Marinas wrote:
> On Thu, Sep 25, 2025 at 08:00:40PM +0100, Mark Brown wrote:

> > Yeah, just I need to convince myself that we're always running the
> > exit_mm() path in the context of the exiting thread.  Like you say it
> > needs checking but hopefully you're right and the current code is more
> > correct than I had thought.

> The only path to gcs_free() is via mm_release() -> deactivate_mm().
> mm_release() is called from either exit_mm_release() or
> exec_mm_release(). These two functions are only called with current and
> current->mm.

> I guess for historical reasons, they take task and mm parameters but in
> recent mainline, they don't seem to get anything other than current.

Thanks for checking for me.  I guess some refactoring might be in
order to make all this clear.

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