4.10-stable review patch. If anyone has any objections, please let me know.
------------------ From: Niklas Cassel <[email protected]> commit 17fcbd590d0c3e35bd9646e2215f86586378bc42 upstream. We hang if SIGKILL has been sent, but the task is stuck in down_read() (after do_exit()), even though no task is doing down_write() on the rwsem in question: INFO: task libupnp:21868 blocked for more than 120 seconds. libupnp D 0 21868 1 0x08100008 ... Call Trace: __schedule() schedule() __down_read() do_exit() do_group_exit() __wake_up_parent() This bug has already been fixed for CONFIG_RWSEM_XCHGADD_ALGORITHM=y in the following commit: 04cafed7fc19 ("locking/rwsem: Fix down_write_killable()") ... however, this bug also exists for CONFIG_RWSEM_GENERIC_SPINLOCK=y. Signed-off-by: Niklas Cassel <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Niklas Cassel <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Fixes: d47996082f52 ("locking/rwsem: Introduce basis for down_write_killable()") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/locking/rwsem-spinlock.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) --- a/kernel/locking/rwsem-spinlock.c +++ b/kernel/locking/rwsem-spinlock.c @@ -216,10 +216,8 @@ int __sched __down_write_common(struct r */ if (sem->count == 0) break; - if (signal_pending_state(state, current)) { - ret = -EINTR; - goto out; - } + if (signal_pending_state(state, current)) + goto out_nolock; set_task_state(tsk, state); raw_spin_unlock_irqrestore(&sem->wait_lock, flags); schedule(); @@ -227,12 +225,19 @@ int __sched __down_write_common(struct r } /* got the lock */ sem->count = -1; -out: list_del(&waiter.list); raw_spin_unlock_irqrestore(&sem->wait_lock, flags); return ret; + +out_nolock: + list_del(&waiter.list); + if (!list_empty(&sem->wait_list)) + __rwsem_do_wake(sem, 1); + raw_spin_unlock_irqrestore(&sem->wait_lock, flags); + + return -EINTR; } void __sched __down_write(struct rw_semaphore *sem)
