mainline inclusion
from mainline-v6.2-rc1
commit f571faf6
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I7R8WG

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f571faf6e443b6011ccb585d57866177af1f643c

--------------------------------

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.

Expose new interfaces for this: timer_shutdown_sync() and timer_shutdown().

timer_shutdown_sync() has the same functionality as timer_delete_sync()
plus the NULL-ification of the timer function.

timer_shutdown() has the same functionality as timer_delete() plus the
NULL-ification of the timer function.

In both cases the rearming of the timer is prevented by silently discarding
rearm attempts due to timer->function being NULL.
Co-developed-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Tested-by: NGuenter Roeck <linux@roeck-us.net>
Reviewed-by: NJacob Keller <jacob.e.keller@intel.com>
Reviewed-by: NAnna-Maria Behnsen <anna-maria@linutronix.de>
Link: https://lore.kernel.org/all/20220407161745.7d6754b3@gandalf.local.home
Link: https://lore.kernel.org/all/20221110064101.429013735@goodmis.org
Link: https://lore.kernel.org/r/20221123201625.314230270@linutronix.deSigned-off-by: NYu Liao <liaoyu15@huawei.com>