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timers: Use del_timer_sync() even on UP 

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
This commit is contained in:
Thomas Gleixner 2022-11-23 21:18:42 +01:00
parent 14f043f134
commit 168f6b6ffb
2 changed files with 1 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/timer.h
View File

@ -183,12 +183,7 @@ 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
extern int del_timer_sync(struct timer_list *timer);
extern void init_timers(void);
struct hrtimer;

2
kernel/time/timer.c
View File

@ -1396,7 +1396,6 @@ 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
@ -1477,7 +1476,6 @@ 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 *),