diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2019-11-06 22:55:42 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-12-05 15:38:27 +0100 |
| commit | 0633e316e2a8bbea17949ae85c9cebf3a67eeaa1 (patch) | |
| tree | 844552eb84e484702e4b7b69f4ac7e93d3f9f617 /kernel | |
| parent | 1be36de0acdc5d58d8e2510b8b35c6d97c881451 (diff) | |
futex: Sanitize exit state handling
commit 4a8e991b91aca9e20705d434677ac013974e0e30 upstream.
Instead of having a smp_mb() and an empty lock/unlock of task::pi_lock move
the state setting into to the lock section.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191106224556.645603214@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/futex.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 4960e327c375..fac0c1747396 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -3726,16 +3726,19 @@ void futex_exit_recursive(struct task_struct *tsk) void futex_exit_release(struct task_struct *tsk) { - tsk->futex_state = FUTEX_STATE_EXITING; - /* - * Ensure that all new tsk->pi_lock acquisitions must observe - * FUTEX_STATE_EXITING. Serializes against attach_to_pi_owner(). - */ - smp_mb(); /* - * Ensure that we must observe the pi_state in exit_pi_state_list(). + * Switch the state to FUTEX_STATE_EXITING under tsk->pi_lock. + * + * This ensures that all subsequent checks of tsk->futex_state in + * attach_to_pi_owner() must observe FUTEX_STATE_EXITING with + * tsk->pi_lock held. + * + * It guarantees also that a pi_state which was queued right before + * the state change under tsk->pi_lock by a concurrent waiter must + * be observed in exit_pi_state_list(). */ raw_spin_lock_irq(&tsk->pi_lock); + tsk->futex_state = FUTEX_STATE_EXITING; raw_spin_unlock_irq(&tsk->pi_lock); futex_exec_release(tsk); |