Commit 259c2fbe authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'locking-urgent-2020-11-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull locking fixes from Thomas Gleixner:
 "Two fixes for the locking subsystem:

   - Prevent an unconditional interrupt enable in a futex helper
     function which can be called from contexts which expect interrupts
     to stay disabled across the call

   - Don't modify lockdep chain keys in the validation process as that
     causes chain inconsistency"

* tag 'locking-urgent-2020-11-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  lockdep: Avoid to modify chain keys in validate_chain()
  futex: Don't enable IRQs unconditionally in put_pi_state()
parents a50cf159 d61fc96a

kernel/futex.c

+3 −2
Original line number Diff line number Diff line
@@ -788,8 +788,9 @@ static void put_pi_state(struct futex_pi_state *pi_state) 
	 */

	if (pi_state->owner) {

		struct task_struct *owner;

		unsigned long flags;



		raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);

		raw_spin_lock_irqsave(&pi_state->pi_mutex.wait_lock, flags);

		owner = pi_state->owner;

		if (owner) {

			raw_spin_lock(&owner->pi_lock);
@@ -797,7 +798,7 @@ static void put_pi_state(struct futex_pi_state *pi_state) 
			raw_spin_unlock(&owner->pi_lock);

		}

		rt_mutex_proxy_unlock(&pi_state->pi_mutex, owner);

		raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);

		raw_spin_unlock_irqrestore(&pi_state->pi_mutex.wait_lock, flags);

	}



	if (current->pi_state_cache) {

kernel/locking/lockdep.c

+9 −10
Original line number Diff line number Diff line
@@ -2765,7 +2765,9 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, 
 * (Note that this has to be done separately, because the graph cannot

 * detect such classes of deadlocks.)

 *

 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read

 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same

 * lock class is held but nest_lock is also held, i.e. we rely on the

 * nest_lock to avoid the deadlock.

 */

static int

check_deadlock(struct task_struct *curr, struct held_lock *next)
@@ -2788,7 +2790,7 @@ check_deadlock(struct task_struct *curr, struct held_lock *next) 
		 * lock class (i.e. read_lock(lock)+read_lock(lock)):

		 */

		if ((next->read == 2) && prev->read)

			return 2;

			continue;



		/*

		 * We're holding the nest_lock, which serializes this lock's
@@ -3592,16 +3594,13 @@ static int validate_chain(struct task_struct *curr, 


		if (!ret)

			return 0;

		/*

		 * Mark recursive read, as we jump over it when

		 * building dependencies (just like we jump over

		 * trylock entries):

		 */

		if (ret == 2)

			hlock->read = 2;

		/*

		 * Add dependency only if this lock is not the head

		 * of the chain, and if it's not a secondary read-lock:

		 * of the chain, and if the new lock introduces no more

		 * lock dependency (because we already hold a lock with the

		 * same lock class) nor deadlock (because the nest_lock

		 * serializes nesting locks), see the comments for

		 * check_deadlock().

		 */

		if (!chain_head && ret != 2) {

			if (!check_prevs_add(curr, hlock))

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