From patchwork Tue Nov 22 17:45:10 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 13052625 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 073C8C4332F for ; Tue, 22 Nov 2022 17:47:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234651AbiKVRrM (ORCPT ); Tue, 22 Nov 2022 12:47:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33100 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234570AbiKVRqG (ORCPT ); Tue, 22 Nov 2022 12:46:06 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B18F84331; Tue, 22 Nov 2022 09:45:12 -0800 (PST) Message-ID: <20221122173649.018971915@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1669139110; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=87QZpCh0faCKJGN7E79B+YLvDwCLrhCyE7zZDe+9ZyU=; b=wtECrHcC+cQJKedJl/ID7HXmlF6xyPU87K1kIEWbWThYdz0SdPyIMyKiTohxMyXNZSN03+ lNqkCwWLR/rNJrh7piFsu58WJuoaS4Klh40CVnY9khH4RfaxRvaylrH3qNJNRIuYslFmQG WzWnDENmC+bBjqzmhuJ2EjyX1ycQ+14FeNBBllrPV9ndwhgQkie3iH2Cn8jB6u2hT9B6tn vT/LV+B8iyUdS97JWLQ6uebM5DtVQVHQdhRSJeX/g6s4adiQmXIwkXIGfUdCi6xrJ+x0Zt 9x4WfDQ1950Vev1ue9cVttlHp44YB2TJrNEbNEPKBzR1PpCda1PPeRQS6+6Nxg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1669139110; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=87QZpCh0faCKJGN7E79B+YLvDwCLrhCyE7zZDe+9ZyU=; b=jZfQFAaa7z5EeBEPsw/N6W/viHAdTgwJVIkjofEh/cCCE12KwADUYOs2/fkJk2Dvqo3t03 h3cUnBpFVKqYrOAA== From: Thomas Gleixner To: LKML Cc: Linus Torvalds , Steven Rostedt , Anna-Maria Behnsen , Peter Zijlstra , Stephen Boyd , Guenter Roeck , Andrew Morton , Julia Lawall , Arnd Bergmann , Viresh Kumar , Marc Zyngier , Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , linux-bluetooth@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org Subject: [patch V2 16/17] timers: Update the documentation to reflect on the new timer_shutdown() API References: <20221122171312.191765396@linutronix.de> MIME-Version: 1.0 Date: Tue, 22 Nov 2022 18:45:10 +0100 (CET) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: "Steven Rostedt (Google)" In order to make sure that a timer is not re-armed after it is stopped before freeing, a new shutdown state is added to the timer code. The API timer_shutdown_sync() and timer_shutdown() must be called before the object that holds the timer can be freed. Update the documentation to reflect this new workflow. [ tglx: Updated to the new semantics and updated the zh_CN version ] Signed-off-by: Steven Rostedt (Google) Signed-off-by: Thomas Gleixner Tested-by: Guenter Roeck Link: https://lore.kernel.org/r/20221110064147.712934793@goodmis.org --- Documentation/RCU/Design/Requirements/Requirements.rst | 2 +- Documentation/core-api/local_ops.rst | 2 +- Documentation/kernel-hacking/locking.rst | 5 +++++ Documentation/translations/zh_CN/core-api/local_ops.rst | 2 +- 4 files changed, 8 insertions(+), 3 deletions(-) --- a/Documentation/RCU/Design/Requirements/Requirements.rst +++ b/Documentation/RCU/Design/Requirements/Requirements.rst @@ -1858,7 +1858,7 @@ unloaded. After a given module has been one of its functions results in a segmentation fault. The module-unload functions must therefore cancel any delayed calls to loadable-module functions, for example, any outstanding mod_timer() must be dealt -with via timer_delete_sync() or similar. +with via timer_shutdown_sync() or similar. Unfortunately, there is no way to cancel an RCU callback; once you invoke call_rcu(), the callback function is eventually going to be --- a/Documentation/core-api/local_ops.rst +++ b/Documentation/core-api/local_ops.rst @@ -191,7 +191,7 @@ Here is a sample module which implements static void __exit test_exit(void) { - timer_delete_sync(&test_timer); + timer_shutdown_sync(&test_timer); } module_init(test_init); --- a/Documentation/kernel-hacking/locking.rst +++ b/Documentation/kernel-hacking/locking.rst @@ -1007,6 +1007,11 @@ calling add_timer() at the end of their Because this is a fairly common case which is prone to races, you should use timer_delete_sync() (``include/linux/timer.h``) to handle this case. +Before freeing a timer, timer_shutdown() or timer_shutdown_sync() should be +called which will keep it from being rearmed. Any subsequent attempt to +rearm the timer will be silently ignored by the core code. + + Locking Speed ============= --- a/Documentation/translations/zh_CN/core-api/local_ops.rst +++ b/Documentation/translations/zh_CN/core-api/local_ops.rst @@ -185,7 +185,7 @@ UP之间没有不同的行为，在你� static void __exit test_exit(void) { - timer_delete_sync(&test_timer); + timer_shutdown_sync(&test_timer); } module_init(test_init);