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authorSteven Rostedt (Google) <rostedt@goodmis.org>2022-11-23 21:18:55 +0100
committerThomas Gleixner <tglx@linutronix.de>2022-11-24 15:09:12 +0100
commita31323bef2b66455920d054b160c17d4240f8fd4 (patch)
treeb7c9ba77bc3b47b7333e2024a3668bcd30c763e9
parentf571faf6e443b6011ccb585d57866177af1f643c (diff)
downloadlwn-a31323bef2b66455920d054b160c17d4240f8fd4.tar.gz
lwn-a31323bef2b66455920d054b160c17d4240f8fd4.zip
timers: Update the documentation to reflect on the new timer_shutdown() API
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) <rostedt@goodmis.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de> Link: https://lore.kernel.org/r/20221110064147.712934793@goodmis.org Link: https://lore.kernel.org/r/20221123201625.375284489@linutronix.de
-rw-r--r--Documentation/RCU/Design/Requirements/Requirements.rst2
-rw-r--r--Documentation/core-api/local_ops.rst2
-rw-r--r--Documentation/kernel-hacking/locking.rst5
-rw-r--r--Documentation/translations/zh_CN/core-api/local_ops.rst2
4 files changed, 8 insertions, 3 deletions
diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst
index 546f23abeca3..49387d823619 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 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
diff --git a/Documentation/core-api/local_ops.rst b/Documentation/core-api/local_ops.rst
index a84f8b0c7ab2..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)
{
- timer_delete_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 c5b8678ed232..c756786e17ae 100644
--- a/Documentation/kernel-hacking/locking.rst
+++ b/Documentation/kernel-hacking/locking.rst
@@ -1007,6 +1007,11 @@ calling add_timer() at the end of their timer function).
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
=============
diff --git a/Documentation/translations/zh_CN/core-api/local_ops.rst b/Documentation/translations/zh_CN/core-api/local_ops.rst
index 22493b9b829c..eb5423f60f17 100644
--- 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,在你的架构的 ``local.h`` 中包括 ``asm-g
static void __exit test_exit(void)
{
- timer_delete_sync(&test_timer);
+ timer_shutdown_sync(&test_timer);
}
module_init(test_init);