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SubjectRe: [patch-rt] locking, rwlock-rt: do not save state multiple times in __write_rt_lock()
On 2017-08-09 14:04:48 [+0200], Mike Galbraith wrote:
>
> Save state prior to entering the acquisition loop, otherwise we may
> initially see readers, but upon releasing ->wait_lock see none, loop
> back around, and having not slept, save TASK_UNINTERRUPTIBLE.
>
> Signed-off-by_ Mike Galbraith <efault@gmx.de>

applied but

> ---
> kernel/locking/rwlock-rt.c | 37 ++++++++++++++++++++-----------------
> 1 file changed, 20 insertions(+), 17 deletions(-)
>
> --- a/kernel/locking/rwlock-rt.c
> +++ b/kernel/locking/rwlock-rt.c
> @@ -190,30 +190,33 @@ void __sched __write_rt_lock(struct rt_r

>
> + for (;;) {
> /* Have all readers left the critical region? */
> - if (!atomic_read(&lock->readers)) {
> - atomic_set(&lock->readers, WRITER_BIAS);
> - raw_spin_lock(&self->pi_lock);
> - __set_current_state_no_track(self->saved_state);
> - self->saved_state = TASK_RUNNING;
> - raw_spin_unlock(&self->pi_lock);
> - raw_spin_unlock_irqrestore(&m->wait_lock, flags);
> - return;

I kept this part where it is so the diff is smaller.

> - }
> + if (!atomic_read(&lock->readers))
> + break;
> }
>
> int __write_rt_trylock(struct rt_rw_lock *lock)

Sebastian

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