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Date: Thu, 10 Nov 2022 01:41:07 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: linux-kernel@...r.kernel.org Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, Stephen Boyd <sboyd@...nel.org>, Guenter Roeck <linux@...ck-us.net>, Anna-Maria Gleixner <anna-maria@...utronix.de>, Andrew Morton <akpm@...ux-foundation.org>, Julia Lawall <Julia.Lawall@...ia.fr> Subject: [PATCH v6 6/6] timers: Update the documentation to reflect on the new timer_shutdown() API From: "Steven Rostedt (Google)" <rostedt@...dmis.org> 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. Cc: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Thomas Gleixner <tglx@...utronix.de> Cc: Stephen Boyd <sboyd@...nel.org> Cc: Anna-Maria Gleixner <anna-maria@...utronix.de> Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: Julia Lawall <Julia.Lawall@...ia.fr> Tested-by: Guenter Roeck <linux@...ck-us.net> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org> --- Documentation/RCU/Design/Requirements/Requirements.rst | 2 +- Documentation/core-api/local_ops.rst | 2 +- Documentation/kernel-hacking/locking.rst | 5 +++++ 3 files changed, 7 insertions(+), 2 deletions(-) diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst index a0f8164c8513..ec6de88846b9 100644 --- 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 unloaded, any attempt to call 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 del_timer_sync() or similar. +with via timer_shutdown_sync(). Unfortunately, there is no way to cancel an RCU callback; once you invoke call_rcu(), the callback function is eventually going to be diff --git a/Documentation/core-api/local_ops.rst b/Documentation/core-api/local_ops.rst index 2ac3f9f29845..0b42ceaaf3c4 100644 --- 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 a basic per cpu counter using static void __exit test_exit(void) { - del_timer_sync(&test_timer); + timer_shutdown_sync(&test_timer); } module_init(test_init); diff --git a/Documentation/kernel-hacking/locking.rst b/Documentation/kernel-hacking/locking.rst index 6805ae6e86e6..eb341b69fd15 100644 --- a/Documentation/kernel-hacking/locking.rst +++ b/Documentation/kernel-hacking/locking.rst @@ -1009,6 +1009,11 @@ use del_timer_sync() (``include/linux/timer.h``) to handle this case. It returns the number of times the timer had to be deleted before we finally stopped it from adding itself back in. +Before freeing a timer, timer_shutdown() or timer_shutdown_sync() should be +called which will keep it from being rearmed, although if it is rearmed, it +will produce a warning. + + Locking Speed ============= -- 2.35.1
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