Messages in this thread | | | Date | Sat, 5 Jan 2013 19:29:27 +0100 | Subject | Re: [PATCH tip/core/urgent 1/2] rcu: Prevent soft-lockup complaints about no-CBs CPUs | From | Frederic Weisbecker <> |
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2013/1/5 Paul E. McKenney <paulmck@linux.vnet.ibm.com>: > On Sat, Jan 05, 2013 at 06:21:01PM +0100, Frederic Weisbecker wrote: >> Hi Paul, >> >> 2013/1/5 Paul E. McKenney <paulmck@linux.vnet.ibm.com>: >> > From: Paul Gortmaker <paul.gortmaker@windriver.com> >> > >> > 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 <fweisbec@gmail.com> >> > Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> >> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> >> > --- >> > 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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