Re: [PATCH tip/core/urgent 1/2] rcu: Prevent soft-lockup complaints about no-CBs CPUs
2013/1/5 Paul E. McKenney :
> On Sat, Jan 05, 2013 at 06:21:01PM +0100, Frederic Weisbecker wrote:
>> Hi Paul,
>>
>> 2013/1/5 Paul E. McKenney :
>> > From: Paul Gortmaker
>> >
>> > The wait_event() at the head of the rcu_nocb_kthread() can result in
>> > soft-lockup complaints if the CPU in question does not register RCU
>> > callbacks for an extended period. This commit therefore changes
>> > the wait_event() to a wait_event_interruptible().
>> >
>> > Reported-by: Frederic Weisbecker
>> > Signed-off-by: Paul Gortmaker
>> > Signed-off-by: Paul E. McKenney
>> > ---
>> > kernel/rcutree_plugin.h |3 ++-
>> > 1 files changed, 2 insertions(+), 1 deletions(-)
>> >
>> > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
>> > index f6e5ec2..43dba2d 100644
>> > --- a/kernel/rcutree_plugin.h
>> > +++ b/kernel/rcutree_plugin.h
>> > @@ -2366,10 +2366,11 @@ static int rcu_nocb_kthread(void *arg)
>> > for (;;) {
>> > /* If not polling, wait for next batch of callbacks. */
>> > if (!rcu_nocb_poll)
>> > - wait_event(rdp->nocb_wq, rdp->nocb_head);
>> > + wait_event_interruptible(rdp->nocb_wq,
>> > rdp->nocb_head);
>> > list = ACCESS_ONCE(rdp->nocb_head);
>> > if (!list) {
>> > schedule_timeout_interruptible(1);
>> > + flush_signals(current);
>>
>> Why is that needed?
>
> To satisfy my paranoia. ;-) And in case someone ever figures out some
> way to send a signal to a kthread.
Ok. I don't want to cause any insomnia to anyone, so I won't insist ;)
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Re: [PATCH tip/core/urgent 1/2] rcu: Prevent soft-lockup complaints about no-CBs CPUs
On Sat, Jan 05, 2013 at 06:21:01PM +0100, Frederic Weisbecker wrote:
> Hi Paul,
>
> 2013/1/5 Paul E. McKenney :
> > From: Paul Gortmaker
> >
> > The wait_event() at the head of the rcu_nocb_kthread() can result in
> > soft-lockup complaints if the CPU in question does not register RCU
> > callbacks for an extended period. This commit therefore changes
> > the wait_event() to a wait_event_interruptible().
> >
> > Reported-by: Frederic Weisbecker
> > Signed-off-by: Paul Gortmaker
> > Signed-off-by: Paul E. McKenney
> > ---
> > kernel/rcutree_plugin.h |3 ++-
> > 1 files changed, 2 insertions(+), 1 deletions(-)
> >
> > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
> > index f6e5ec2..43dba2d 100644
> > --- a/kernel/rcutree_plugin.h
> > +++ b/kernel/rcutree_plugin.h
> > @@ -2366,10 +2366,11 @@ static int rcu_nocb_kthread(void *arg)
> > for (;;) {
> > /* If not polling, wait for next batch of callbacks. */
> > if (!rcu_nocb_poll)
> > - wait_event(rdp->nocb_wq, rdp->nocb_head);
> > + wait_event_interruptible(rdp->nocb_wq,
> > rdp->nocb_head);
> > list = ACCESS_ONCE(rdp->nocb_head);
> > if (!list) {
> > schedule_timeout_interruptible(1);
> > + flush_signals(current);
>
> Why is that needed?
To satisfy my paranoia. ;-) And in case someone ever figures out some
way to send a signal to a kthread.
Thanx, Paul
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Re: [PATCH tip/core/urgent 1/2] rcu: Prevent soft-lockup complaints about no-CBs CPUs
Hi Paul,
2013/1/5 Paul E. McKenney :
> From: Paul Gortmaker
>
> The wait_event() at the head of the rcu_nocb_kthread() can result in
> soft-lockup complaints if the CPU in question does not register RCU
> callbacks for an extended period. This commit therefore changes
> the wait_event() to a wait_event_interruptible().
>
> Reported-by: Frederic Weisbecker
> Signed-off-by: Paul Gortmaker
> Signed-off-by: Paul E. McKenney
> ---
> kernel/rcutree_plugin.h |3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
> index f6e5ec2..43dba2d 100644
> --- a/kernel/rcutree_plugin.h
> +++ b/kernel/rcutree_plugin.h
> @@ -2366,10 +2366,11 @@ static int rcu_nocb_kthread(void *arg)
> for (;;) {
> /* If not polling, wait for next batch of callbacks. */
> if (!rcu_nocb_poll)
> - wait_event(rdp->nocb_wq, rdp->nocb_head);
> + wait_event_interruptible(rdp->nocb_wq,
> rdp->nocb_head);
> list = ACCESS_ONCE(rdp->nocb_head);
> if (!list) {
> schedule_timeout_interruptible(1);
> + flush_signals(current);
Why is that needed?
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[PATCH tip/core/urgent 1/2] rcu: Prevent soft-lockup complaints about no-CBs CPUs
From: Paul Gortmaker
The wait_event() at the head of the rcu_nocb_kthread() can result in
soft-lockup complaints if the CPU in question does not register RCU
callbacks for an extended period. This commit therefore changes
the wait_event() to a wait_event_interruptible().
Reported-by: Frederic Weisbecker
Signed-off-by: Paul Gortmaker
Signed-off-by: Paul E. McKenney
---
kernel/rcutree_plugin.h |3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f6e5ec2..43dba2d 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2366,10 +2366,11 @@ static int rcu_nocb_kthread(void *arg)
for (;;) {
/* If not polling, wait for next batch of callbacks. */
if (!rcu_nocb_poll)
- wait_event(rdp->nocb_wq, rdp->nocb_head);
+ wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head);
list = ACCESS_ONCE(rdp->nocb_head);
if (!list) {
schedule_timeout_interruptible(1);
+ flush_signals(current);
continue;
}
--
1.7.8
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