| Message ID | 1401749088.3645.189.camel@edumazet-glaptop2.roam.corp.google.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On Mon, Jun 02, 2014 at 03:44:48PM -0700, Eric Dumazet wrote: > On Mon, 2014-06-02 at 15:08 -0700, Paul E. McKenney wrote: > > > diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c > > index c639556f3fa0..c0120279dead 100644 > > --- a/kernel/rcu/srcu.c > > +++ b/kernel/rcu/srcu.c > > @@ -295,12 +295,15 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct); > > int __srcu_read_lock(struct srcu_struct *sp) > > { > > int idx; > > + unsigned long *lp; > > > > idx = ACCESS_ONCE(sp->completed) & 0x1; > > preempt_disable(); > > - ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) += 1; > > + lp = this_cpu_ptr(&sp->per_cpu_ref->c[idx]); > > + ACCESS_ONCE(*lp) = *lp + 1; > > smp_mb(); /* B */ /* Avoid leaking the critical section. */ > > - ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->seq[idx]) += 1; > > + lp = this_cpu_ptr(&sp->per_cpu_ref->seq[idx]); > > + ACCESS_ONCE(*lp) = *lp + 1; > > preempt_enable(); > > return idx; > > > > This probably could use the following > > diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c > index c639556f3fa0..3a97eb6f9076 100644 > --- a/kernel/rcu/srcu.c > +++ b/kernel/rcu/srcu.c > @@ -298,9 +298,9 @@ int __srcu_read_lock(struct srcu_struct *sp) > > idx = ACCESS_ONCE(sp->completed) & 0x1; > preempt_disable(); > - ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) += 1; > + this_cpu_inc(sp->per_cpu_ref->c[idx]); > smp_mb(); /* B */ /* Avoid leaking the critical section. */ > - ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->seq[idx]) += 1; > + this_cpu_inc(sp->per_cpu_ref->seq[idx]); > preempt_enable(); > return idx; > } Good point! But given that I already have preemption disabled and given that __srcu_read_lock() is not to be used by irq handlers, I should be able to use __this_cpu_inc(), correct? Just to avoid unnecessary irq disabling on non-x86 platforms... Seems to pass a quick build, so trying a bit heavier testing. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 2014-06-02 at 16:17 -0700, Paul E. McKenney wrote: > But given that I already have preemption disabled and given that > __srcu_read_lock() is not to be used by irq handlers, I should be able to > use __this_cpu_inc(), correct? Just to avoid unnecessary irq disabling > on non-x86 platforms... Absolutely, __this_cpu_inc() is OK here. -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Jun 02, 2014 at 04:53:44PM -0700, Eric Dumazet wrote: > On Mon, 2014-06-02 at 16:17 -0700, Paul E. McKenney wrote: > > > But given that I already have preemption disabled and given that > > __srcu_read_lock() is not to be used by irq handlers, I should be able to > > use __this_cpu_inc(), correct? Just to avoid unnecessary irq disabling > > on non-x86 platforms... > > Absolutely, __this_cpu_inc() is OK here. Cool, giving it a test... Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c index c639556f3fa0..3a97eb6f9076 100644 --- a/kernel/rcu/srcu.c +++ b/kernel/rcu/srcu.c @@ -298,9 +298,9 @@ int __srcu_read_lock(struct srcu_struct *sp) idx = ACCESS_ONCE(sp->completed) & 0x1; preempt_disable(); - ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) += 1; + this_cpu_inc(sp->per_cpu_ref->c[idx]); smp_mb(); /* B */ /* Avoid leaking the critical section. */ - ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->seq[idx]) += 1; + this_cpu_inc(sp->per_cpu_ref->seq[idx]); preempt_enable(); return idx; }