Messages in this thread | | | Date | Wed, 23 Jul 2014 05:13:49 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 06/16] rcu: Clear gp_flags only when actually starting new gp |
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On Wed, Jul 23, 2014 at 01:09:43AM -0400, Pranith Kumar wrote: > We are clearing the gp_flags before we check if a grace period is in progress. > If a grace period is in progress, we return after incorrectly clearing the > gp_flags. The code comments say that this is highly unlikely, but just to be > safe this commit moves the clearing of gp_flags to after the check for grace > period in progress. > > Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Sorry, but no. The WARN_ON_ONCE() indicates an error condition. It should not be possible to have a grace period already in progress at this point in the code. So the two locations for the clearing of ->gp_flags are equivalent.
Thanx, Paul
> --- > kernel/rcu/tree.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 044946e..b14cecd 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1605,7 +1605,6 @@ static int rcu_gp_init(struct rcu_state *rsp) > raw_spin_unlock_irq(&rnp->lock); > return 0; > } > - ACCESS_ONCE(rsp->gp_flags) = 0; /* Clear all flags: New grace period. */ > > if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) { > /* > @@ -1616,6 +1615,8 @@ static int rcu_gp_init(struct rcu_state *rsp) > return 0; > } > > + ACCESS_ONCE(rsp->gp_flags) = 0; /* Clear all flags: New grace period. */ > + > /* Advance to a new grace period and initialize state. */ > record_gp_stall_check_time(rsp); > /* Record GP times before starting GP, hence smp_store_release(). */ > -- > 2.0.0.rc2 >
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