tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/tip/tip.git WIP.timers/core head: b16101077c4444bc7e0dde91e7ffb258ce1f979b commit: e51f39feec02940feeb0914ef9ff8fe5e05965c1 [27/68] posix-timer: Use a callback for cancel synchronization reproduce: # apt-get install sparse # sparse version: v0.6.1-rc1-7-g2b96cd8-dirty git checkout e51f39feec02940feeb0914ef9ff8fe5e05965c1 make ARCH=x86_64 allmodconfig make C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
If you fix the issue, kindly add following tag Reported-by: kbuild test robot <[email protected]> sparse warnings: (new ones prefixed by >>) kernel/time/posix-timers.c:588:24: sparse: sparse: context imbalance in '__lock_timer' - different lock contexts for basic block >> include/linux/rcupdate.h:644:9: sparse: sparse: context imbalance in >> 'timer_wait_running' - unexpected unlock kernel/time/posix-timers.c:870:12: sparse: sparse: context imbalance in 'do_timer_settime' - different lock contexts for basic block kernel/time/posix-timers.c:976:1: sparse: sparse: context imbalance in '__se_sys_timer_delete' - different lock contexts for basic block vim +/timer_wait_running +644 include/linux/rcupdate.h ^1da177e4c3f41 Linus Torvalds 2005-04-16 596 ^1da177e4c3f41 Linus Torvalds 2005-04-16 597 /* ^1da177e4c3f41 Linus Torvalds 2005-04-16 598 * So where is rcu_write_lock()? It does not exist, as there is no ^1da177e4c3f41 Linus Torvalds 2005-04-16 599 * way for writers to lock out RCU readers. This is a feature, not ^1da177e4c3f41 Linus Torvalds 2005-04-16 600 * a bug -- this property is what provides RCU's performance benefits. ^1da177e4c3f41 Linus Torvalds 2005-04-16 601 * Of course, writers must coordinate with each other. The normal ^1da177e4c3f41 Linus Torvalds 2005-04-16 602 * spinlock primitives work well for this, but any other technique may be ^1da177e4c3f41 Linus Torvalds 2005-04-16 603 * used as well. RCU does not care how the writers keep out of each ^1da177e4c3f41 Linus Torvalds 2005-04-16 604 * others' way, as long as they do so. ^1da177e4c3f41 Linus Torvalds 2005-04-16 605 */ 3d76c082907e8f Paul E. McKenney 2009-09-28 606 3d76c082907e8f Paul E. McKenney 2009-09-28 607 /** ca5ecddfa8fcbd Paul E. McKenney 2010-04-28 608 * rcu_read_unlock() - marks the end of an RCU read-side critical section. 3d76c082907e8f Paul E. McKenney 2009-09-28 609 * f27bc4873fa8b7 Paul E. McKenney 2014-05-04 610 * In most situations, rcu_read_unlock() is immune from deadlock. f27bc4873fa8b7 Paul E. McKenney 2014-05-04 611 * However, in kernels built with CONFIG_RCU_BOOST, rcu_read_unlock() f27bc4873fa8b7 Paul E. McKenney 2014-05-04 612 * is responsible for deboosting, which it does via rt_mutex_unlock(). f27bc4873fa8b7 Paul E. McKenney 2014-05-04 613 * Unfortunately, this function acquires the scheduler's runqueue and f27bc4873fa8b7 Paul E. McKenney 2014-05-04 614 * priority-inheritance spinlocks. This means that deadlock could result f27bc4873fa8b7 Paul E. McKenney 2014-05-04 615 * if the caller of rcu_read_unlock() already holds one of these locks or ec84b27f9b3b56 Anna-Maria Gleixner 2018-05-25 616 * any lock that is ever acquired while holding them. f27bc4873fa8b7 Paul E. McKenney 2014-05-04 617 * f27bc4873fa8b7 Paul E. McKenney 2014-05-04 618 * That said, RCU readers are never priority boosted unless they were f27bc4873fa8b7 Paul E. McKenney 2014-05-04 619 * preempted. Therefore, one way to avoid deadlock is to make sure f27bc4873fa8b7 Paul E. McKenney 2014-05-04 620 * that preemption never happens within any RCU read-side critical f27bc4873fa8b7 Paul E. McKenney 2014-05-04 621 * section whose outermost rcu_read_unlock() is called with one of f27bc4873fa8b7 Paul E. McKenney 2014-05-04 622 * rt_mutex_unlock()'s locks held. Such preemption can be avoided in f27bc4873fa8b7 Paul E. McKenney 2014-05-04 623 * a number of ways, for example, by invoking preempt_disable() before f27bc4873fa8b7 Paul E. McKenney 2014-05-04 624 * critical section's outermost rcu_read_lock(). f27bc4873fa8b7 Paul E. McKenney 2014-05-04 625 * f27bc4873fa8b7 Paul E. McKenney 2014-05-04 626 * Given that the set of locks acquired by rt_mutex_unlock() might change f27bc4873fa8b7 Paul E. McKenney 2014-05-04 627 * at any time, a somewhat more future-proofed approach is to make sure f27bc4873fa8b7 Paul E. McKenney 2014-05-04 628 * that that preemption never happens within any RCU read-side critical f27bc4873fa8b7 Paul E. McKenney 2014-05-04 629 * section whose outermost rcu_read_unlock() is called with irqs disabled. f27bc4873fa8b7 Paul E. McKenney 2014-05-04 630 * This approach relies on the fact that rt_mutex_unlock() currently only f27bc4873fa8b7 Paul E. McKenney 2014-05-04 631 * acquires irq-disabled locks. f27bc4873fa8b7 Paul E. McKenney 2014-05-04 632 * f27bc4873fa8b7 Paul E. McKenney 2014-05-04 633 * The second of these two approaches is best in most situations, f27bc4873fa8b7 Paul E. McKenney 2014-05-04 634 * however, the first approach can also be useful, at least to those f27bc4873fa8b7 Paul E. McKenney 2014-05-04 635 * developers willing to keep abreast of the set of locks acquired by f27bc4873fa8b7 Paul E. McKenney 2014-05-04 636 * rt_mutex_unlock(). f27bc4873fa8b7 Paul E. McKenney 2014-05-04 637 * 3d76c082907e8f Paul E. McKenney 2009-09-28 638 * See rcu_read_lock() for more information. 3d76c082907e8f Paul E. McKenney 2009-09-28 639 */ bc33f24bdca8b6 Paul E. McKenney 2009-08-22 640 static inline void rcu_read_unlock(void) bc33f24bdca8b6 Paul E. McKenney 2009-08-22 641 { f78f5b90c4ffa5 Paul E. McKenney 2015-06-18 642 RCU_LOCKDEP_WARN(!rcu_is_watching(), bde23c6892878e Heiko Carstens 2012-02-01 643 "rcu_read_unlock() used illegally while idle"); bc33f24bdca8b6 Paul E. McKenney 2009-08-22 @644 __release(RCU); bc33f24bdca8b6 Paul E. McKenney 2009-08-22 645 __rcu_read_unlock(); d24209bb689e2c Paul E. McKenney 2015-01-21 646 rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */ bc33f24bdca8b6 Paul E. McKenney 2009-08-22 647 } ^1da177e4c3f41 Linus Torvalds 2005-04-16 648 :::::: The code at line 644 was first introduced by commit :::::: bc33f24bdca8b6e97376e3a182ab69e6cdefa989 rcu: Consolidate sparse and lockdep declarations in include/linux/rcupdate.h :::::: TO: Paul E. McKenney <[email protected]> :::::: CC: Ingo Molnar <[email protected]> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
