From b0b0aa5d858d4d2fe39a5e4486e0550e858108f6 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 23 Nov 2022 21:18:31 +0100 Subject: Documentation: Remove bogus claim about del_timer_sync() del_timer_sync() does not return the number of times it tried to delete the timer which rearms itself. It's clearly documented: The function returns whether it has deactivated a pending timer or not. This part of the documentation is from 2003 where del_timer_sync() really returned the number of deletion attempts for unknown reasons. The code was rewritten in 2005, but the documentation was not updated. Signed-off-by: Thomas Gleixner Reviewed-by: Jacob Keller Reviewed-by: Anna-Maria Behnsen Link: https://lore.kernel.org/r/20221123201624.452282769@linutronix.de --- Documentation/kernel-hacking/locking.rst | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'Documentation/kernel-hacking') diff --git a/Documentation/kernel-hacking/locking.rst b/Documentation/kernel-hacking/locking.rst index 6805ae6e86e6..b26e4a3a9b7e 100644 --- a/Documentation/kernel-hacking/locking.rst +++ b/Documentation/kernel-hacking/locking.rst @@ -1006,8 +1006,7 @@ Another common problem is deleting timers which restart themselves (by 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 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. +handle this case. Locking Speed ============= -- cgit v1.2.3 From 87bdd932e85881895d4720255b40ac28749c4e32 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 23 Nov 2022 21:18:47 +0100 Subject: Documentation: Replace del_timer/del_timer_sync() Adjust to the new preferred function names. Suggested-by: Steven Rostedt Signed-off-by: Thomas Gleixner Reviewed-by: Jacob Keller Reviewed-by: Anna-Maria Behnsen Link: https://lore.kernel.org/r/20221123201625.075320635@linutronix.de --- Documentation/RCU/Design/Requirements/Requirements.rst | 2 +- Documentation/core-api/local_ops.rst | 2 +- Documentation/kernel-hacking/locking.rst | 11 +++++------ Documentation/timers/hrtimers.rst | 2 +- Documentation/translations/it_IT/kernel-hacking/locking.rst | 10 +++++----- Documentation/translations/zh_CN/core-api/local_ops.rst | 2 +- 6 files changed, 14 insertions(+), 15 deletions(-) (limited to 'Documentation/kernel-hacking') diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst index a0f8164c8513..546f23abeca3 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_delete_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 2ac3f9f29845..a84f8b0c7ab2 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_delete_sync(&test_timer); } module_init(test_init); diff --git a/Documentation/kernel-hacking/locking.rst b/Documentation/kernel-hacking/locking.rst index b26e4a3a9b7e..c5b8678ed232 100644 --- a/Documentation/kernel-hacking/locking.rst +++ b/Documentation/kernel-hacking/locking.rst @@ -967,7 +967,7 @@ you might do the following:: while (list) { struct foo *next = list->next; - del_timer(&list->timer); + timer_delete(&list->timer); kfree(list); list = next; } @@ -981,7 +981,7 @@ the lock after we spin_unlock_bh(), and then try to free the element (which has already been freed!). This can be avoided by checking the result of -del_timer(): if it returns 1, the timer has been deleted. +timer_delete(): if it returns 1, the timer has been deleted. If 0, it means (in this case) that it is currently running, so we can do:: @@ -990,7 +990,7 @@ do:: while (list) { struct foo *next = list->next; - if (!del_timer(&list->timer)) { + if (!timer_delete(&list->timer)) { /* Give timer a chance to delete this */ spin_unlock_bh(&list_lock); goto retry; @@ -1005,8 +1005,7 @@ do:: Another common problem is deleting timers which restart themselves (by 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 del_timer_sync() (``include/linux/timer.h``) to -handle this case. +use timer_delete_sync() (``include/linux/timer.h``) to handle this case. Locking Speed ============= @@ -1334,7 +1333,7 @@ lock. - kfree() -- add_timer() and del_timer() +- add_timer() and timer_delete() Mutex API reference =================== diff --git a/Documentation/timers/hrtimers.rst b/Documentation/timers/hrtimers.rst index c1c20a693e8f..7ac448908d1f 100644 --- a/Documentation/timers/hrtimers.rst +++ b/Documentation/timers/hrtimers.rst @@ -118,7 +118,7 @@ existing timer wheel code, as it is mature and well suited. Sharing code was not really a win, due to the different data structures. Also, the hrtimer functions now have clearer behavior and clearer names - such as hrtimer_try_to_cancel() and hrtimer_cancel() [which are roughly -equivalent to del_timer() and del_timer_sync()] - so there's no direct +equivalent to timer_delete() and timer_delete_sync()] - so there's no direct 1:1 mapping between them on the algorithmic level, and thus no real potential for code sharing either. diff --git a/Documentation/translations/it_IT/kernel-hacking/locking.rst b/Documentation/translations/it_IT/kernel-hacking/locking.rst index eddfba806e13..b8ecf41273c5 100644 --- a/Documentation/translations/it_IT/kernel-hacking/locking.rst +++ b/Documentation/translations/it_IT/kernel-hacking/locking.rst @@ -990,7 +990,7 @@ potreste fare come segue:: while (list) { struct foo *next = list->next; - del_timer(&list->timer); + timer_delete(&list->timer); kfree(list); list = next; } @@ -1003,7 +1003,7 @@ e prenderà il *lock* solo dopo spin_unlock_bh(), e cercherà di eliminare il suo oggetto (che però è già stato eliminato). Questo può essere evitato controllando il valore di ritorno di -del_timer(): se ritorna 1, il temporizzatore è stato già +timer_delete(): se ritorna 1, il temporizzatore è stato già rimosso. Se 0, significa (in questo caso) che il temporizzatore è in esecuzione, quindi possiamo fare come segue:: @@ -1012,7 +1012,7 @@ esecuzione, quindi possiamo fare come segue:: while (list) { struct foo *next = list->next; - if (!del_timer(&list->timer)) { + if (!timer_delete(&list->timer)) { /* Give timer a chance to delete this */ spin_unlock_bh(&list_lock); goto retry; @@ -1026,7 +1026,7 @@ esecuzione, quindi possiamo fare come segue:: Un altro problema è l'eliminazione dei temporizzatori che si riavviano da soli (chiamando add_timer() alla fine della loro esecuzione). Dato che questo è un problema abbastanza comune con una propensione -alle corse critiche, dovreste usare del_timer_sync() +alle corse critiche, dovreste usare timer_delete_sync() (``include/linux/timer.h``) per gestire questo caso. Velocità della sincronizzazione @@ -1372,7 +1372,7 @@ contesto, o trattenendo un qualsiasi *lock*. - kfree() -- add_timer() e del_timer() +- add_timer() e timer_delete() Riferimento per l'API dei Mutex =============================== diff --git a/Documentation/translations/zh_CN/core-api/local_ops.rst b/Documentation/translations/zh_CN/core-api/local_ops.rst index 41e4525038e8..22493b9b829c 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) { - del_timer_sync(&test_timer); + timer_delete_sync(&test_timer); } module_init(test_init); -- cgit v1.2.3 From a31323bef2b66455920d054b160c17d4240f8fd4 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" Date: Wed, 23 Nov 2022 21:18:55 +0100 Subject: 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) Signed-off-by: Thomas Gleixner Tested-by: Guenter Roeck Reviewed-by: Jacob Keller Reviewed-by: Anna-Maria Behnsen Link: https://lore.kernel.org/r/20221110064147.712934793@goodmis.org Link: https://lore.kernel.org/r/20221123201625.375284489@linutronix.de --- 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(-) (limited to 'Documentation/kernel-hacking') 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); -- cgit v1.2.3