linux-kernel - [PATCH 5.15.y 13/14] timers: Update the documentation to reflect on the new timer

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Message-Id: <20251128160539.358938-14-aha310510@gmail.com>
Date: Sat, 29 Nov 2025 01:05:38 +0900
From: Jeongjun Park <aha310510@...il.com>
To: stable@...r.kernel.org
Cc: gregkh@...uxfoundation.org,
	tglx@...utronix.de,
	Julia.Lawall@...ia.fr,
	akpm@...ux-foundation.org,
	anna-maria@...utronix.de,
	arnd@...db.de,
	linux-bluetooth@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux@...ck-us.net,
	luiz.dentz@...il.com,
	marcel@...tmann.org,
	maz@...nel.org,
	peterz@...radead.org,
	rostedt@...dmis.org,
	sboyd@...nel.org,
	viresh.kumar@...aro.org,
	aha310510@...il.com,
	linux-staging@...ts.linux.dev,
	Jacob Keller <jacob.e.keller@...el.com>
Subject: [PATCH 5.15.y 13/14] timers: Update the documentation to reflect on the new timer_shutdown() API

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

[ Upstream commit a31323bef2b66455920d054b160c17d4240f8fd4 ]

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@...dmis.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Guenter Roeck <linux@...ck-us.net>
Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>
Reviewed-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Link: https://lore.kernel.org/r/20221110064147.712934793@goodmis.org
Link: https://lore.kernel.org/r/20221123201625.375284489@linutronix.de
Signed-off-by: Jeongjun Park <aha310510@...il.com>
---
 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(-)

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 c447d55fa080..3bbb11ba647a 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
 
+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);
--