On Wed 11-05-16 11:41:28, Peter Zijlstra wrote: > On Wed, May 11, 2016 at 11:31:27AM +0200, Michal Hocko wrote: > > > Care to cook up a full patch? > > compile tested only, if someone could please test it?
I have tried to run the test case from Tetsuo[1] with a small printk to show the interrupted writer case: [ 2753.596678] XXX: Writer interrupted. Woken waiters:0 [ 2998.266978] XXX: Writer interrupted. Woken waiters:0 which means rwsem_atomic_update(-RWSEM_WAITING_BIAS, sem) path which is the problematic case. oom_reaper was always able to succeed so I guess the patch works as expected. I will leave the test run for longer to be sure. [1] http://lkml.kernel.org/r/201605061958.hhg48967.jvftslfqofo...@i-love.sakura.ne.jp > > I'll go write a Changelog if it turns out to actually work ;-) > > --- > kernel/locking/rwsem-xadd.c | 21 +++++++++++++++------ > 1 file changed, 15 insertions(+), 6 deletions(-) > > diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c > index df4dcb883b50..09e30c6225e5 100644 > --- a/kernel/locking/rwsem-xadd.c > +++ b/kernel/locking/rwsem-xadd.c > @@ -487,23 +487,32 @@ __rwsem_down_write_failed_common(struct rw_semaphore > *sem, int state) > > /* Block until there are no active lockers. */ > do { > - if (signal_pending_state(state, current)) { > - raw_spin_lock_irq(&sem->wait_lock); > - ret = ERR_PTR(-EINTR); > - goto out; > - } > + if (signal_pending_state(state, current)) > + goto out_nolock; > + > schedule(); > set_current_state(state); > } while ((count = sem->count) & RWSEM_ACTIVE_MASK); > > raw_spin_lock_irq(&sem->wait_lock); > } > -out: > __set_current_state(TASK_RUNNING); > list_del(&waiter.list); > raw_spin_unlock_irq(&sem->wait_lock); > > return ret; > + > +out_nolock: > + __set_current_state(TASK_RUNNING); > + raw_spin_lock_irq(&sem->wait_lock); > + list_del(&waiter.list); > + if (list_empty(&sem->wait_list)) > + rwsem_atomic_update(-RWSEM_WAITING_BIAS, sem); > + else > + __rwsem_do_wake(sem, RWSEM_WAKE_ANY); > + raw_spin_unlock_irq(&sem->wait_lock); > + > + return ERR_PTR(-EINTR); > } > > __visible struct rw_semaphore * __sched -- Michal Hocko SUSE Labs
