diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-11-15 09:25:43 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-11-15 09:25:43 -0800 |
| commit | 259c2fbef8f09cec8ac3d67820ca6778242beeaa (patch) | |
| tree | 9d6f13a8e0a1d379897495c7e3678fca556a8ea5 | |
| parent | a50cf15906d4d0ad1d6bb32e9eeeb282899a8180 (diff) | |
| parent | d61fc96a37603384cd531622c1e89de1096b5123 (diff) | |
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()
| -rw-r--r-- | kernel/futex.c | 5 | ||||
| -rw-r--r-- | kernel/locking/lockdep.c | 19 |
2 files changed, 12 insertions, 12 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index ac328874f6e5..00259c7e288e 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -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) { diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index b71ad8d9f1c9..d9fb9e19d2ed 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -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 @@ -3593,15 +3595,12 @@ 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)) |