Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:

 - Add 'cross-release' support to lockdep, which allows APIs like
   completions, where it's not the 'owner' who releases the lock, to be
   tracked. It's all activated automatically under
   CONFIG_PROVE_LOCKING=y.

 - Clean up (restructure) the x86 atomics op implementation to be more
   readable, in preparation of KASAN annotations. (Dmitry Vyukov)

 - Fix static keys (Paolo Bonzini)

 - Add killable versions of down_read() et al (Kirill Tkhai)

 - Rework and fix jump_label locking (Marc Zyngier, Paolo Bonzini)

 - Rework (and fix) tlb_flush_pending() barriers (Peter Zijlstra)

 - Remove smp_mb__before_spinlock() and convert its usages, introduce
   smp_mb__after_spinlock() (Peter Zijlstra)

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (56 commits)
  locking/lockdep/selftests: Fix mixed read-write ABBA tests
  sched/completion: Avoid unnecessary stack allocation for COMPLETION_INITIALIZER_ONSTACK()
  acpi/nfit: Fix COMPLETION_INITIALIZER_ONSTACK() abuse
  locking/pvqspinlock: Relax cmpxchg's to improve performance on some architectures
  smp: Avoid using two cache lines for struct call_single_data
  locking/lockdep: Untangle xhlock history save/restore from task independence
  locking/refcounts, x86/asm: Disable CONFIG_ARCH_HAS_REFCOUNT for the time being
  futex: Remove duplicated code and fix undefined behaviour
  Documentation/locking/atomic: Finish the document...
  locking/lockdep: Fix workqueue crossrelease annotation
  workqueue/lockdep: 'Fix' flush_work() annotation
  locking/lockdep/selftests: Add mixed read-write ABBA tests
  mm, locking/barriers: Clarify tlb_flush_pending() barriers
  locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS truly non-interactive
  locking/lockdep: Explicitly initialize wq_barrier::done::map
  locking/lockdep: Rename CONFIG_LOCKDEP_COMPLETE to CONFIG_LOCKDEP_COMPLETIONS
  locking/lockdep: Reword title of LOCKDEP_CROSSRELEASE config
  locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE part of CONFIG_PROVE_LOCKING
  locking/refcounts, x86/asm: Implement fast refcount overflow protection
  locking/lockdep: Fix the rollback and overwrite detection logic in crossrelease
  ...

1 files changed, 43 insertions, 10 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ca937b0c3a96..ab3c0dc8c7ed 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2091,8 +2091,30 @@ __acquires(&pool->lock)
 
 	spin_unlock_irq(&pool->lock);
 
-	lock_map_acquire_read(&pwq->wq->lockdep_map);
+	lock_map_acquire(&pwq->wq->lockdep_map);
 	lock_map_acquire(&lockdep_map);
+	/*
+	 * Strictly speaking we should mark the invariant state without holding
+	 * any locks, that is, before these two lock_map_acquire()'s.
+	 *
+	 * However, that would result in:
+	 *
+	 *   A(W1)
+	 *   WFC(C)
+	 *		A(W1)
+	 *		C(C)
+	 *
+	 * Which would create W1->C->W1 dependencies, even though there is no
+	 * actual deadlock possible. There are two solutions, using a
+	 * read-recursive acquire on the work(queue) 'locks', but this will then
+	 * hit the lockdep limitation on recursive locks, or simply discard
+	 * these locks.
+	 *
+	 * AFAICT there is no possible deadlock scenario between the
+	 * flush_work() and complete() primitives (except for single-threaded
+	 * workqueues), so hiding them isn't a problem.
+	 */
+	lockdep_invariant_state(true);
 	trace_workqueue_execute_start(work);
 	worker->current_func(work);
 	/*
@@ -2474,7 +2496,16 @@ static void insert_wq_barrier(struct pool_workqueue *pwq,
 	 */
 	INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
 	__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
-	init_completion(&barr->done);
+
+	/*
+	 * Explicitly init the crosslock for wq_barrier::done, make its lock
+	 * key a subkey of the corresponding work. As a result we won't
+	 * build a dependency between wq_barrier::done and unrelated work.
+	 */
+	lockdep_init_map_crosslock((struct lockdep_map *)&barr->done.map,
+				   "(complete)wq_barr::done",
+				   target->lockdep_map.key, 1);
+	__init_completion(&barr->done);
 	barr->task = current;
 
 	/*
@@ -2815,16 +2846,18 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
 	spin_unlock_irq(&pool->lock);
 
 	/*
-	 * If @max_active is 1 or rescuer is in use, flushing another work
-	 * item on the same workqueue may lead to deadlock.  Make sure the
-	 * flusher is not running on the same workqueue by verifying write
-	 * access.
+	 * Force a lock recursion deadlock when using flush_work() inside a
+	 * single-threaded or rescuer equipped workqueue.
+	 *
+	 * For single threaded workqueues the deadlock happens when the work
+	 * is after the work issuing the flush_work(). For rescuer equipped
+	 * workqueues the deadlock happens when the rescuer stalls, blocking
+	 * forward progress.
 	 */
-	if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)
+	if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer) {
 		lock_map_acquire(&pwq->wq->lockdep_map);
-	else
-		lock_map_acquire_read(&pwq->wq->lockdep_map);
-	lock_map_release(&pwq->wq->lockdep_map);
+		lock_map_release(&pwq->wq->lockdep_map);
+	}
 
 	return true;
 already_gone: