diff options
Diffstat (limited to 'kernel/locking/mutex.c')
| -rw-r--r-- | kernel/locking/mutex.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 89350f924c85..14b9cca36b05 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -26,6 +26,7 @@ #include <linux/interrupt.h> #include <linux/debug_locks.h> #include <linux/osq_lock.h> +#include <linux/delay.h> /* * In the DEBUG case we are using the "NULL fastpath" for mutexes, @@ -378,6 +379,17 @@ static bool mutex_optimistic_spin(struct mutex *lock, * values at the cost of a few extra spins. */ cpu_relax_lowlatency(); + + /* + * On arm systems, we must slow down the waiter's repeated + * aquisition of spin_mlock and atomics on the lock count, or + * we risk starving out a thread attempting to release the + * mutex. The mutex slowpath release must take spin lock + * wait_lock. This spin lock can share a monitor with the + * other waiter atomics in the mutex data structure, so must + * take care to rate limit the waiters. + */ + udelay(1); } osq_unlock(&lock->osq); |