linux-kernel - Re: [PATCH] arm64/gcs: Don't call gcs_free() during flush

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Message-ID: <6901c30b-0b31-4c9c-9943-e5205485691e@sirena.org.uk>
Date: Thu, 12 Jun 2025 17:44:18 +0100
From: Mark Brown <broonie@...nel.org>
To: Will Deacon <will@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/gcs: Don't call gcs_free() during flush_gcs()

On Thu, Jun 12, 2025 at 05:20:28PM +0100, Will Deacon wrote:

> Having looking a little at the code, I think that
> arch_release_task_struct() might be better than deactivate_mm(). The
> latter takes an 'mm' parameter which we ignore but I think happens to
> be 'current->mm'and so things work. Given that, and that we don't do any
> GCS management on the activate_mm() path, freeing the GCS in the
> task-centric functions makes more sense to me.

The issue with that is that we only call arch_release_task_struct()
quite late, after the mm has been disassociated from the task.
do_exit() cleans up the mm with exit_mm() relatively early on, and
free_task() which is what calls arch_release_task_struct() is one of the
last things we do as we clean up.

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