atomic_add_return() invalidates the cache line in other processors where-as atomic_read does not. I don't see why we would need invalidation in this case. If indeed it was need a comment would be helpful for readers. Otherwise doesn't using atomic_read() make more sense here? RFC!
replace atomic_add_return(0, v) with atomic_read(v) as the latter is better. Signed-off-by: Pranith Kumar <[email protected]> --- 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 dac6d20..a4a8f5f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -891,7 +891,7 @@ static int rcu_is_cpu_rrupt_from_idle(void) static int dyntick_save_progress_counter(struct rcu_data *rdp, bool *isidle, unsigned long *maxj) { - rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); + rdp->dynticks_snap = atomic_read(&rdp->dynticks->dynticks); rcu_sysidle_check_cpu(rdp, isidle, maxj); if ((rdp->dynticks_snap & 0x1) == 0) { trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); @@ -920,7 +920,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, int *rcrmp; unsigned int snap; - curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); + curr = (unsigned int)atomic_read(&rdp->dynticks->dynticks); snap = (unsigned int)rdp->dynticks_snap; /* -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
