timers: Use del_timer_sync() even on UP

mainline inclusion
from mainline-v6.2-rc1
commit 168f6b6f
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=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: 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/20221123201624.888306160@linutronix.deSigned-off-by: NYu Liao <liaoyu15@huawei.com>
(cherry picked from commit 39923cb6)

include/linux/timer.h

@@ -189,12 +189,7 @@ 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);
 extern void run_local_timers(void);

kernel/time/timer.c

@@ -1343,7 +1343,6 @@ 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
@@ -1417,7 +1416,6 @@ 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 *),