Messages in this thread | | | Date | Wed, 23 Jul 2014 05:26:08 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 11/16] rcu: Check for spurious wakeup using return value |
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On Wed, Jul 23, 2014 at 01:09:48AM -0400, Pranith Kumar wrote: > When the gp_kthread wakes up from the wait event, it returns 0 if the wake up is > due to the condition having been met. This commit checks this return value > for a spurious wake up before calling rcu_gp_init(). > > Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
How does this added check help? I don't see that it does. If the flag is set, we want to wake up. If we get a spurious wakeup, but then the flag gets set before we actually wake up, we still want to wake up.
So sorry, but no.
Thanx, Paul
PS. BTW, the ones that I am not immediately responding to are those that I will recheck later on and possibly accept.
> --- > kernel/rcu/tree.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index f8847d9..3b20ad2 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1790,11 +1790,11 @@ static int __noreturn rcu_gp_kthread(void *arg) > ACCESS_ONCE(rsp->gpnum), > TPS("reqwait")); > rsp->gp_state = RCU_GP_WAIT_GPS; > - wait_event_interruptible(rsp->gp_wq, > + ret = wait_event_interruptible(rsp->gp_wq, > ACCESS_ONCE(rsp->gp_flags) & > RCU_GP_FLAG_INIT); > /* Locking provides needed memory barrier. */ > - if (rcu_gp_init(rsp)) > + if (!ret && rcu_gp_init(rsp)) > break; > cond_resched(); > flush_signals(current); > -- > 2.0.0.rc2 >
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