Commit f0b422a0 authored Nov 23, 2022 by Thomas Gleixner Committed by Greg Kroah-Hartman Apr 13, 2024

timers: Use del_timer_sync() even on UP

[ Upstream commit 168f6b6ffbeec0b9333f3582e4cf637300858db5 ]

del_timer_sync() is assumed to be pointless on uniprocessor systems and can
be mapped to del_timer() because in theory del_timer() can never be invoked
while the timer callback function is executed.

This is not entirely true because del_timer() can be invoked from interrupt
context and therefore hit in the middle of a running timer callback.

Contrary to that del_timer_sync() is not allowed to be invoked from
interrupt context unless the affected timer is marked with TIMER_IRQSAFE.
del_timer_sync() has proper checks in place to detect such a situation.

Give up on the UP optimization and make del_timer_sync() unconditionally
available.

Co-developed-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Anna-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/20221123201624.888306160@linutronix.de

Stable-dep-of: 0f7352557a35 ("wifi: brcmfmac: Fix use-after-free bug in brcmf_cfg80211_detach")
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 26e9278a

include/linux/timer.h

+1 −6

Original line number	Diff line number	Diff line
		@@ -171,12 +171,7 @@ extern int timer_reduce(struct timer_list *timer, unsigned long expires);
		extern void add_timer(struct timer_list *timer);

		extern int try_to_del_timer_sync(struct timer_list *timer);

		#if defined(CONFIG_SMP) \|\| defined(CONFIG_PREEMPT_RT)
		extern int del_timer_sync(struct timer_list *timer);
		#else
		# define del_timer_sync(t) del_timer(t)
		#endif

		#define del_singleshot_timer_sync(t) del_timer_sync(t)

+0 −2

Original line number	Diff line number	Diff line
		@@ -1349,7 +1349,6 @@ static inline void timer_sync_wait_running(struct timer_base *base) { }
		static inline void del_timer_wait_running(struct timer_list *timer) { }
		#endif

		#if defined(CONFIG_SMP) \|\| defined(CONFIG_PREEMPT_RT)
		/**
		* del_timer_sync - Deactivate a timer and wait for the handler to finish.
		* @timer: The timer to be deactivated
		@@ -1423,7 +1422,6 @@ int del_timer_sync(struct timer_list *timer)
		return ret;
		}
		EXPORT_SYMBOL(del_timer_sync);
		#endif

		static void call_timer_fn(struct timer_list *timer,
		void (fn)(struct timer_list ),