From: Thomas Gleixner <tglx@kernel.org>
To: FUJITA Tomonori <tomo@flapping.org>,
a.hindborg@kernel.org, anna-maria@linutronix.de,
frederic@kernel.org, gary@garyguo.net, ojeda@kernel.org
Cc: acourbot@nvidia.com, aliceryhl@google.com,
bjorn3_gh@protonmail.com, boqun@kernel.org, dakr@kernel.org,
daniel.almeida@collabora.com, jstultz@google.com,
lossin@kernel.org, lyude@redhat.com, sboyd@kernel.org,
tamird@kernel.org, tmgross@umich.edu, work@onurozkan.dev,
linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
FUJITA Tomonori <fujita.tomonori@gmail.com>
Subject: Re: [PATCH v1 1/2] hrtimer: Add hrtimer_forward_safe_from_callback()
Date: Mon, 09 Nov 2026 22:11:43 +0100 [thread overview]
Message-ID: <871p8tvhf4.ffs@fw13> (raw)
In-Reply-To: <20261101232829.593680-2-tomo@flapping.org>
On Mon, Nov 02 2026 at 08:28, FUJITA Tomonori wrote:
> From: FUJITA Tomonori <fujita.tomonori@gmail.com>
>
> A hrtimer can be started while its callback runs. hrtimer_forward()
> writes the expiry without the base lock, so the caller has to serialize
> it against a concurrent hrtimer_start(). Otherwise the write can change
> the sort key of a queued timer.
>
> Add a variant which does the check and the update with the base lock
> held. If the timer is already queued, the expiry is left alone and the
> expiry set by hrtimer_start() wins.
>
> The first user is the Rust hrtimer abstraction. Safe Rust code can
> start a timer while its callback runs, so forward() in the callback
> can only be a safe API if the core handles a concurrent start.
>
> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> Link: https://lore.kernel.org/all/877bk3ixp5.ffs@fw13/
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
I don't have anything conflicting at the moment, so this can go through
the rust tree.
Reviewed-by: Thomas Gleixner <tglx@kernel.org>
next prev parent reply other threads:[~2026-11-09 21:11 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-01 23:28 [PATCH v1 0/2] hrtimer: Add hrtimer_forward_safe_from_callback() FUJITA Tomonori
2026-11-01 23:28 ` [PATCH v1 1/2] " FUJITA Tomonori
2026-11-09 21:11 ` Thomas Gleixner [this message]
2026-11-01 23:28 ` [PATCH v1 2/2] rust: hrtimer: Use hrtimer_forward_safe_from_callback() FUJITA Tomonori
2026-11-02 14:31 ` Andreas Hindborg
2026-11-03 2:17 ` FUJITA Tomonori
2026-11-03 9:35 ` Andreas Hindborg
2026-11-12 12:47 ` [PATCH v1 0/2] hrtimer: Add hrtimer_forward_safe_from_callback() Andreas Hindborg
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