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Commit 17fcbd59 authored by Niklas Cassel's avatar Niklas Cassel Committed by Ingo Molnar
Browse files

locking/rwsem: Fix down_write_killable() for CONFIG_RWSEM_GENERIC_SPINLOCK=y 



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:

 04cafed7 ("locking/rwsem: Fix down_write_killable()")

... however, this bug also exists for CONFIG_RWSEM_GENERIC_SPINLOCK=y.

Signed-off-by: default avatarNiklas Cassel <niklas.cassel@axis.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
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: d4799608 ("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: default avatarIngo Molnar <mingo@kernel.org>
parent 9bbb25af

kernel/locking/rwsem-spinlock.c

+11 −5
Original line number Diff line number Diff line
@@ -213,10 +213,9 @@ 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_current_state(state);

		raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

		schedule();
@@ -224,12 +223,19 @@ 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)