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authorNiklas Cassel <niklas.cassel@axis.com>2017-02-25 01:17:53 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-03-22 12:43:40 +0100
commitc40609652267440ae6f800303ea1f3be17d357e2 (patch)
treec46f4fb37764ae6e8cf26f2f58dcb5e73f4d3014
parent1522181f4bc14a61c72981439fcbe9a87496f3cf (diff)
locking/rwsem: Fix down_write_killable() for CONFIG_RWSEM_GENERIC_SPINLOCK=y
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 <niklas.cassel@axis.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <mhocko@suse.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Niklas Cassel <niklass@axis.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: d47996082f52 ("locking/rwsem: Introduce basis for down_write_killable()") Link: http://lkml.kernel.org/r/1487981873-12649-1-git-send-email-niklass@axis.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/locking/rwsem-spinlock.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/kernel/locking/rwsem-spinlock.c b/kernel/locking/rwsem-spinlock.c
index 1591f6b3539f..2bef4ab94003 100644
--- a/kernel/locking/rwsem-spinlock.c
+++ b/kernel/locking/rwsem-spinlock.c
@@ -216,10 +216,8 @@ int __sched __down_write_common(struct rw_semaphore *sem, int state)
*/
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 rw_semaphore *sem, int state)
}
/* 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)