From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17E88231C91 for ; Tue, 30 Dec 2025 15:55:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767110159; cv=none; b=nCjL7TQqj64ruX3S2nLIxxdCUiI6W4psJjQhpY/IAxJnLplmRyAohSs2fCEzj5GL6XpwbogByMmXirVF8oOH2kYpN2rVTGzinQ2pScTabyMt20C4VE8c88ExPEAiQPgqy0YwmBF4P3VeHFpCbU+UF4BTdye246Prar+pXIAldCw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767110159; c=relaxed/simple; bh=pd1zGF06Q30h3mG7ucXBSPRmqdRQnXdZm1RywwH2OaY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TEHEVJnV2u6K7WnKiSxHUhKIqbjf5vppnPYJPqrZXQgZxwkcvm1mDYzJG4GNPv6DdkaN/66QJ+pSXgodYhB/CaBJlltvBHnL7yu8/VRK/pI8InbHt58j7sCCLTcLr2NyuCeub9R5kuthHibnXltrlT7vSrXxLFf5U0Z+uuuOSNQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=byYy1/J8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="byYy1/J8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31C7CC4CEFB; Tue, 30 Dec 2025 15:55:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767110158; bh=pd1zGF06Q30h3mG7ucXBSPRmqdRQnXdZm1RywwH2OaY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=byYy1/J8nkI62YpFQUY//CGMfJ0KV7y1Z9M3TOt5nHKMPQP3Jw1/6NMNxEQI9D7t7 0eKDvGT7Fct/jpwdPwH/ObW3q+EiOmvanIxDVdBcaQWKcX+fPZIsv7UTkFMeKjYzZS 7qpPkpLarMZTlqQH5m3saoEeyTqXSSsizfY/tWon2ietnDWksoO+v5H3MXcA+fyZrI EWjQYQminjPlXCRgqusiqn4ciWT1iypvZFM+0XSM77CJZFHEEY62QS0zHpsJZUUGHy +lfmRVVJiykAXjcrPCN8Y4RY9ZGUGNzgzolrR5zoaUre8Wo0Nniy6av+i8/Uq6ABbl sNKG2tbuqezNQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Nam Cao , Thomas Gleixner , Sasha Levin Subject: [PATCH 6.12.y 1/3] hrtimers: Introduce hrtimer_update_function() Date: Tue, 30 Dec 2025 10:55:54 -0500 Message-ID: <20251230155556.2289800-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025122923-amaretto-output-f3dc@gregkh> References: <2025122923-amaretto-output-f3dc@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Nam Cao [ Upstream commit 8f02e3563bb5824eb01c94f2c75f1dcee2d05625 ] Some users of hrtimer need to change the callback function after the initial setup. They write to hrtimer::function directly. That's not safe under all circumstances as the write is lockless and a concurrent timer expiry might end up using the wrong function pointer. Introduce hrtimer_update_function(), which also performs runtime checks whether it is safe to modify the callback. This allows to make hrtimer::function private once all users are converted. Signed-off-by: Nam Cao Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20a937b0ae09ad54b5b6d86eabead7c570f1b72e.1730386209.git.namcao@linutronix.de Stable-dep-of: 267ee93c417e ("serial: xilinx_uartps: fix rs485 delay_rts_after_send") Signed-off-by: Sasha Levin --- include/linux/hrtimer.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 6caaa62d2b1f..39fbeb64a7da 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -337,6 +337,28 @@ static inline int hrtimer_callback_running(struct hrtimer *timer) return timer->base->running == timer; } +/** + * hrtimer_update_function - Update the timer's callback function + * @timer: Timer to update + * @function: New callback function + * + * Only safe to call if the timer is not enqueued. Can be called in the callback function if the + * timer is not enqueued at the same time (see the comments above HRTIMER_STATE_ENQUEUED). + */ +static inline void hrtimer_update_function(struct hrtimer *timer, + enum hrtimer_restart (*function)(struct hrtimer *)) +{ + guard(raw_spinlock_irqsave)(&timer->base->cpu_base->lock); + + if (WARN_ON_ONCE(hrtimer_is_queued(timer))) + return; + + if (WARN_ON_ONCE(!function)) + return; + + timer->function = function; +} + /* Forward a hrtimer so it expires after now: */ extern u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval); -- 2.51.0