On 12/10, David Hildenbrand wrote:
>
> > Why active_writer should see .puts_pending != 0 if this is called
> > right after cpu_hotplug_begin() takes cpu_hotplug.lock but before
> > it sets TASK_UNINTERRUPTIBLE?
>
> get_online_cpus() increased the refcount.
> put_online_cpus() will increment puts_pe
> (sorry if this was already discussed, I ignored most of my emails
> I got this week)
>
> On 12/09, David Hildenbrand wrote:
> >
> > @@ -116,7 +118,13 @@ void put_online_cpus(void)
> > if (cpu_hotplug.active_writer == current)
> > return;
> > if (!mutex_trylock(&cpu_hotplug.l
On Wed, Dec 10, 2014 at 01:26:19AM +0100, Oleg Nesterov wrote:
> On 12/09, Paul E. McKenney wrote:
> >
> > Would wait_event()/wake_up() work for the wakeup-writer case?
>
> Yes, and in this case we could probably kill this puts_pending logic
> and avoid cpu_hotplug.lock in put_online_cpus() altoge
On 12/09, Paul E. McKenney wrote:
>
> Would wait_event()/wake_up() work for the wakeup-writer case?
Yes, and in this case we could probably kill this puts_pending logic
and avoid cpu_hotplug.lock in put_online_cpus() altogether? Can't we
just make cpu_hotplug.refcount atomic_t?
Anyway, this makes
(sorry if this was already discussed, I ignored most of my emails
I got this week)
On 12/09, David Hildenbrand wrote:
>
> @@ -116,7 +118,13 @@ void put_online_cpus(void)
> if (cpu_hotplug.active_writer == current)
> return;
> if (!mutex_trylock(&cpu_hotplug.lock)) {
> +
On Tue, Dec 09, 2014 at 05:24:27PM +0100, David Hildenbrand wrote:
> > On Tue, Dec 09, 2014 at 01:23:31PM +0100, David Hildenbrand wrote:
> > > Commit b2c4623dcd07 ("rcu: More on deadlock between CPU hotplug and
> > > expedited
> > > grace periods") introduced another problem that can easily be re
> On Tue, Dec 09, 2014 at 01:23:31PM +0100, David Hildenbrand wrote:
> > Commit b2c4623dcd07 ("rcu: More on deadlock between CPU hotplug and
> > expedited
> > grace periods") introduced another problem that can easily be reproduced by
> > starting/stopping cpus in a loop.
> >
> > E.g.:
> > for
On Tue, Dec 09, 2014 at 01:23:31PM +0100, David Hildenbrand wrote:
> Commit b2c4623dcd07 ("rcu: More on deadlock between CPU hotplug and expedited
> grace periods") introduced another problem that can easily be reproduced by
> starting/stopping cpus in a loop.
>
> E.g.:
> for i in `seq 5000`; do
Commit b2c4623dcd07 ("rcu: More on deadlock between CPU hotplug and expedited
grace periods") introduced another problem that can easily be reproduced by
starting/stopping cpus in a loop.
E.g.:
for i in `seq 5000`; do
echo 1 > /sys/devices/system/cpu/cpu1/online
echo 0 > /sys/devices
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