linux-kernel - Re: [PATCH] arm64/gcs: Don't call gcs_free() when releasing task

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Message-ID: <aG0YizySqTc475JW@willie-the-truck>
Date: Tue, 8 Jul 2025 14:09:31 +0100
From: Will Deacon <will@...nel.org>
To: Mark Brown <broonie@...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() when releasing
 task_struct

On Wed, Jun 25, 2025 at 07:56:34PM +0100, Mark Brown wrote:
> Currently we call gcs_free() when releasing task_struct but this is
> redundant, it attempts to deallocate any kernel managed userspace GCS
> which should no longer be relevant and resets values in the struct we're
> in the process of freeing.
> 
> By the time arch_release_task_struct() is called the mm will have been
> disassociated from the task so the check for a mm in gcs_free() will
> always be false, for threads that are exiting leaving the mm active
> deactivate_mm() will have been called previously and freed any kernel
> managed GCS.
> 
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>  arch/arm64/kernel/process.c | 1 -
>  1 file changed, 1 deletion(-)

Thanks, but please can you also update/remove the stale comment in
gcs_free() which refers to exit_thread() for some reason?

Cheers,

Will