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SubjectRe: [PATCH 03/11] locking, rwsem: introduce basis for down_write_killable
On Wed, May 11, 2016 at 10:28:53AM +0200, Michal Hocko wrote:

> Does the following look correct/reasonable? This is absolutely untested
> and more for a discussion:

I would much rather see it in common; something like so perhaps.

---
kernel/locking/rwsem-xadd.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index df4dcb883b50..5d7f2831a475 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -487,11 +487,9 @@ __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);
@@ -504,6 +502,18 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
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_READERS);
+ raw_spin_unlock_irq(&sem->wait_lock);
+
+ return ERR_PTR(-EINTR);
}

__visible struct rw_semaphore * __sched
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