On Wed, 23 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. > > In those cases it is desired to shutdown the timer in a way which prevents > rearming of the timer. The mechanism to do so is to set timer->function to > NULL and use this as an indicator for the timer arming functions to ignore > the (re)arm request. > > Add a shutdown argument to the relevant internal functions which makes the > actual deactivation code set timer->function to NULL which in turn prevents > rearming of the timer. > > 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> > Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx> > Link: https://lore.kernel.org/all/20220407161745.7d6754b3@xxxxxxxxxxxxxxxxxx > Link: https://lore.kernel.org/all/20221110064101.429013735@xxxxxxxxxxx > --- > V2: Add missing commata (Steven) > V3: Changelog updates (Anna-Maria) > --- > kernel/time/timer.c | 64 ++++++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 55 insertions(+), 9 deletions(-) > > --- a/kernel/time/timer.c > +++ b/kernel/time/timer.c > @@ -1297,14 +1297,21 @@ void add_timer_on(struct timer_list *tim > EXPORT_SYMBOL_GPL(add_timer_on); > > /** > - * __timer_delete - Internal function: Deactivate a timer. > + * __timer_delete - Internal function: Deactivate a timer Some more NIT: You already updated the line a patch before. Maybe remove the dot in the patch before and you get rid of this unneccessary delete/insert of the above line in this hunk. > * @timer: The timer to be deactivated > + * @shutdown: If true, this indicates that the timer is about to be > + * shutdown permanently. > + * > + * If @shutdown is true then @timer->function is set to NULL under the > + * timer base lock which prevents further rearming of the time. In that > + * case any attempt to rearm @timer after this function returns will be > + * silently ignored. > * > * Return: > * * %0 - The timer was not pending > * * %1 - The timer was pending and deactivated > */ > -static int __timer_delete(struct timer_list *timer) > +static int __timer_delete(struct timer_list *timer, bool shutdown) > { > struct timer_base *base; > unsigned long flags; Thanks, Anna-Maria
