Linus,
please pull the latest locking/urgent branch from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
locking-urgent-2020-11-15
up to: d61fc96a3760: lockdep: Avoid to modify chain keys in validate_chain()
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.
Thanks,
tglx
------------------>
Boqun Feng (1):
lockdep: Avoid to modify chain keys in validate_chain()
Dan Carpenter (1):
futex: Don't enable IRQs unconditionally in put_pi_state()
kernel/futex.c | 5 +++--
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
@@ -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))
