On Tue, 22 Nov 2022, Thomas Gleixner wrote: > Tearing down timers which have circular dependencies to other > functionality, e.g. workqueues, where the timer can schedule work and work > can arm timers is not trivial. NIT (comma is missing): can arm timer, is not trivial. > In those cases it is desired to shutdown the timer in a way which prevents > rearming of the timer. The mechanism to do so it to set timer->function to s/to do so it/to do so is/ > NULL and use this as an indicator for the timer arming functions to ignore > the (re)arm request. > > In preparation for that replace the warnings in the relevant code pathes > with checks for timer->function == NULL and discard the rearm request > silently. Here is a verb missing that this is a grammatically correct (and understandable) sentence. > Add debug_assert_init() instead of the WARN_ON_ONCE(!timer->function) > checks so that debug objects can warn about non-initialized timers. > > If developers fail to enable debug objects and then waste lots of time to > figure out why their non-initialized timer is not firing, they deserve it. > > Co-developed-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx> > Link: https://lore.kernel.org/all/20220407161745.7d6754b3@xxxxxxxxxxxxxxxxxx > Link: https://lore.kernel.org/all/20221110064101.429013735@xxxxxxxxxxx > --- > V2: Use continue instead of return and amend the return value docs (Steven) > --- > kernel/time/timer.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 55 insertions(+), 5 deletions(-) > > --- a/kernel/time/timer.c > +++ b/kernel/time/timer.c > @@ -1128,8 +1144,12 @@ static inline int > * mod_timer_pending() is the same for pending timers as mod_timer(), but > * will not activate inactive timers. > * > + * If @timer->function == NULL then the start operation is silently > + * discarded. > + * > * Return: > - * * %0 - The timer was inactive and not modified > + * * %0 - The timer was inactive and not modified or was is in > + * shutdown state and the operation was discarded Do you mean "was" or "is"? Please have also a look at the places where you use the same phrase. > * * %1 - The timer was active and requeued to expire at @expires > */ > int mod_timer_pending(struct timer_list *timer, unsigned long expires) > @@ -1155,8 +1175,12 @@ EXPORT_SYMBOL(mod_timer_pending); > * same timer, then mod_timer() is the only safe way to modify the timeout, > * since add_timer() cannot modify an already running timer. > * > + * If @timer->function == NULL then the start operation is silently > + * discarded, the return value is 0 and meaningless. It's easier to read, if you make a dot instead of comma. Thanks, Anna-Maria
