[tglx-devel:timers/posix 8/14] kernel/time/posix-timers.c:852 timer_wait_running() warn: inconsistent returns '&timer->it_lock'.

[kernel test robot <lkp@intel.com>]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
TO: Thomas Gleixner <tglx@linutronix.de>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git timers/posix
head:   2f9ae35230ff61b3caa708359c745f375cf0c075
commit: 029c3a43aaca2ffc86a970704b469733b70fe88b [8/14] posix-timers: Rework timer removal
:::::: branch date: 17 hours ago
:::::: commit date: 24 hours ago
config: x86_64-randconfig-161-20250225 (https://download.01.org/0day-ci/archive/20250225/202502250737.fMTOUVfQ-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202502250737.fMTOUVfQ-lkp@intel.com/

smatch warnings:
kernel/time/posix-timers.c:852 timer_wait_running() warn: inconsistent returns '&timer->it_lock'.

vim +852 kernel/time/posix-timers.c

ec8f954a40da8c Thomas Gleixner     2019-08-02  800  
0bee3b601b77db Frederic Weisbecker 2019-08-20  801  /*
7d990902664506 Thomas Gleixner     2023-04-25  802   * On PREEMPT_RT this prevents priority inversion and a potential livelock
7d990902664506 Thomas Gleixner     2023-04-25  803   * against the ksoftirqd thread in case that ksoftirqd gets preempted while
7d990902664506 Thomas Gleixner     2023-04-25  804   * executing a hrtimer callback.
7d990902664506 Thomas Gleixner     2023-04-25  805   *
7d990902664506 Thomas Gleixner     2023-04-25  806   * See the comments in hrtimer_cancel_wait_running(). For PREEMPT_RT=n this
7d990902664506 Thomas Gleixner     2023-04-25  807   * just results in a cpu_relax().
7d990902664506 Thomas Gleixner     2023-04-25  808   *
7d990902664506 Thomas Gleixner     2023-04-25  809   * For POSIX CPU timers with CONFIG_POSIX_CPU_TIMERS_TASK_WORK=n this is
7d990902664506 Thomas Gleixner     2023-04-25  810   * just a cpu_relax(). With CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y this
7d990902664506 Thomas Gleixner     2023-04-25  811   * prevents spinning on an eventually scheduled out task and a livelock
7d990902664506 Thomas Gleixner     2023-04-25  812   * when the task which tries to delete or disarm the timer has preempted
7d990902664506 Thomas Gleixner     2023-04-25  813   * the task which runs the expiry in task work context.
0bee3b601b77db Frederic Weisbecker 2019-08-20  814   */
029c3a43aaca2f Thomas Gleixner     2025-02-20  815  static struct k_itimer *timer_wait_running(struct k_itimer *timer, unsigned long *flags,
029c3a43aaca2f Thomas Gleixner     2025-02-20  816  					   bool delete)
6945e5c2abe008 Thomas Gleixner     2019-07-31  817  {
ec8f954a40da8c Thomas Gleixner     2019-08-02  818  	const struct k_clock *kc = READ_ONCE(timer->kclock);
6945e5c2abe008 Thomas Gleixner     2019-07-31  819  	timer_t timer_id = READ_ONCE(timer->it_id);
6945e5c2abe008 Thomas Gleixner     2019-07-31  820  
ec8f954a40da8c Thomas Gleixner     2019-08-02  821  	/* Prevent kfree(timer) after dropping the lock */
ec8f954a40da8c Thomas Gleixner     2019-08-02  822  	rcu_read_lock();
da7ae390d73a82 Thomas Gleixner     2025-02-20  823  	spin_unlock_irqrestore(&timer->it_lock, *flags);
ec8f954a40da8c Thomas Gleixner     2019-08-02  824  
f7abf14f0001a5 Thomas Gleixner     2023-04-17  825  	/*
029c3a43aaca2f Thomas Gleixner     2025-02-20  826  	 * kc->timer_wait_running() might drop RCU lock. So @timer cannot
029c3a43aaca2f Thomas Gleixner     2025-02-20  827  	 * be touched anymore after the function returns, except when
029c3a43aaca2f Thomas Gleixner     2025-02-20  828  	 * @delete is true!
f7abf14f0001a5 Thomas Gleixner     2023-04-17  829  	 */
ec8f954a40da8c Thomas Gleixner     2019-08-02  830  	if (!WARN_ON_ONCE(!kc->timer_wait_running))
ec8f954a40da8c Thomas Gleixner     2019-08-02  831  		kc->timer_wait_running(timer);
ec8f954a40da8c Thomas Gleixner     2019-08-02  832  
ec8f954a40da8c Thomas Gleixner     2019-08-02  833  	rcu_read_unlock();
029c3a43aaca2f Thomas Gleixner     2025-02-20  834  
029c3a43aaca2f Thomas Gleixner     2025-02-20  835  	/*
029c3a43aaca2f Thomas Gleixner     2025-02-20  836  	 * On deletion the timer has been marked invalid before
029c3a43aaca2f Thomas Gleixner     2025-02-20  837  	 * timer_delete_hook() has been invoked. That means that the
029c3a43aaca2f Thomas Gleixner     2025-02-20  838  	 * current task is the only one which has access to the timer and
029c3a43aaca2f Thomas Gleixner     2025-02-20  839  	 * even after dropping timer::it_lock above, no other thread can
029c3a43aaca2f Thomas Gleixner     2025-02-20  840  	 * have accessed the timer.
029c3a43aaca2f Thomas Gleixner     2025-02-20  841  	 */
029c3a43aaca2f Thomas Gleixner     2025-02-20  842  	if (delete) {
029c3a43aaca2f Thomas Gleixner     2025-02-20  843  		spin_lock_irqsave(&timer->it_lock, *flags);
029c3a43aaca2f Thomas Gleixner     2025-02-20  844  		return timer;
029c3a43aaca2f Thomas Gleixner     2025-02-20  845  	}
029c3a43aaca2f Thomas Gleixner     2025-02-20  846  
029c3a43aaca2f Thomas Gleixner     2025-02-20  847  	/*
029c3a43aaca2f Thomas Gleixner     2025-02-20  848  	 * If invoked from timer_set() the timer could have been deleted
029c3a43aaca2f Thomas Gleixner     2025-02-20  849  	 * after dropping the lock. So in that case the timer needs to be
029c3a43aaca2f Thomas Gleixner     2025-02-20  850  	 * looked up and validated.
029c3a43aaca2f Thomas Gleixner     2025-02-20  851  	 */
6945e5c2abe008 Thomas Gleixner     2019-07-31 @852  	return lock_timer(timer_id, flags);
6945e5c2abe008 Thomas Gleixner     2019-07-31  853  }
6945e5c2abe008 Thomas Gleixner     2019-07-31  854  

:::::: The code at line 852 was first introduced by commit
:::::: 6945e5c2abe008302b20266248d6de95575311a8 posix-timers: Rework cancel retry loops

:::::: TO: Thomas Gleixner <tglx@linutronix.de>
:::::: CC: Thomas Gleixner <tglx@linutronix.de>

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