On Mon, 05 Dec 2016, Oleg Nesterov wrote:
Yes. But percpu_down_write() should not be used after exit_notify(), so we
can rely on rcu_read_lock(), release_task()->call_rcu(delayed_put_task_struct)
can't be called until an exiting task passes exit_notify().
But then we probably need
On Mon, 05 Dec 2016, Oleg Nesterov wrote:
Yes. But percpu_down_write() should not be used after exit_notify(), so we
can rely on rcu_read_lock(), release_task()->call_rcu(delayed_put_task_struct)
can't be called until an exiting task passes exit_notify().
But then we probably need
On 12/05, Peter Zijlstra wrote:
>
> > + for (;;) {
> > + set_current_state(TASK_UNINTERRUPTIBLE);
> > +
> > + if (readers_active_check(sem))
> > + break;
> > +
> > + schedule();
> > + }
> > +
> > + rcu_assign_pointer(sem->writer, NULL);
>
> And
On 12/05, Peter Zijlstra wrote:
>
> > + for (;;) {
> > + set_current_state(TASK_UNINTERRUPTIBLE);
> > +
> > + if (readers_active_check(sem))
> > + break;
> > +
> > + schedule();
> > + }
> > +
> > + rcu_assign_pointer(sem->writer, NULL);
>
> And
On 12/02, Davidlohr Bueso wrote:
>
> @@ -102,8 +103,13 @@ void __percpu_up_read(struct percpu_rw_semaphore *sem)
>*/
> __this_cpu_dec(*sem->read_count);
>
> + rcu_read_lock();
> + writer = rcu_dereference(sem->writer);
> +
> /* Prod writer to recheck readers_active */
>
On 12/02, Davidlohr Bueso wrote:
>
> @@ -102,8 +103,13 @@ void __percpu_up_read(struct percpu_rw_semaphore *sem)
>*/
> __this_cpu_dec(*sem->read_count);
>
> + rcu_read_lock();
> + writer = rcu_dereference(sem->writer);
> +
> /* Prod writer to recheck readers_active */
>
On 12/05, Oleg Nesterov wrote:
>
> Yes, but on a second thought task_rcu_dereference() won't really help,
I forgot to explain why, see below.
> #define xxx_wait_event(xxx, event) {
> // comment to explain why
> WARN_ON(current->exit_state);
Otherwise this
On 12/05, Oleg Nesterov wrote:
>
> Yes, but on a second thought task_rcu_dereference() won't really help,
I forgot to explain why, see below.
> #define xxx_wait_event(xxx, event) {
> // comment to explain why
> WARN_ON(current->exit_state);
Otherwise this
Davidlohr, Peter, I'll try to read this patch later, just one note.
On 12/05, Peter Zijlstra wrote:
>
> On Fri, Dec 02, 2016 at 06:18:39PM -0800, Davidlohr Bueso wrote:
> > @@ -102,8 +103,13 @@ void __percpu_up_read(struct percpu_rw_semaphore *sem)
> > */
> >
Davidlohr, Peter, I'll try to read this patch later, just one note.
On 12/05, Peter Zijlstra wrote:
>
> On Fri, Dec 02, 2016 at 06:18:39PM -0800, Davidlohr Bueso wrote:
> > @@ -102,8 +103,13 @@ void __percpu_up_read(struct percpu_rw_semaphore *sem)
> > */
> >
On Fri, Dec 02, 2016 at 06:18:39PM -0800, Davidlohr Bueso wrote:
> @@ -102,8 +103,13 @@ void __percpu_up_read(struct percpu_rw_semaphore *sem)
>*/
> __this_cpu_dec(*sem->read_count);
>
> + rcu_read_lock();
> + writer = rcu_dereference(sem->writer);
Don't think this is
On Fri, Dec 02, 2016 at 06:18:39PM -0800, Davidlohr Bueso wrote:
> @@ -102,8 +103,13 @@ void __percpu_up_read(struct percpu_rw_semaphore *sem)
>*/
> __this_cpu_dec(*sem->read_count);
>
> + rcu_read_lock();
> + writer = rcu_dereference(sem->writer);
Don't think this is
The use of any kind of wait queue is an overkill for pcpu-rwsems.
While one option would be to use the less heavy simple (swait)
flavor, this is still too much for what pcpu-rwsems needs. For one,
we do not care about any sort of queuing in that the only (rare) time
writers (and readers, for that
The use of any kind of wait queue is an overkill for pcpu-rwsems.
While one option would be to use the less heavy simple (swait)
flavor, this is still too much for what pcpu-rwsems needs. For one,
we do not care about any sort of queuing in that the only (rare) time
writers (and readers, for that
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