On Wed, Dec 15, 2021 at 1:58 PM Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > > On 2021-12-13 09:37:36 [-0300], Wander Lairson Costa wrote: > > --- > > block/blk-cgroup.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c > > index 663aabfeba18..0a532bb3003c 100644 > > --- a/block/blk-cgroup.c > > +++ b/block/blk-cgroup.c > > @@ -1911,7 +1911,7 @@ void blk_cgroup_bio_start(struct bio *bio) > > struct blkg_iostat_set *bis; > > unsigned long flags; > > > > - cpu = get_cpu(); > > + cpu = get_cpu_light(); > > bis = per_cpu_ptr(bio->bi_blkg->iostat_cpu, cpu); > > flags = u64_stats_update_begin_irqsave(&bis->sync); > > > > @@ -1928,7 +1928,7 @@ void blk_cgroup_bio_start(struct bio *bio) > > u64_stats_update_end_irqrestore(&bis->sync, flags); > > if (cgroup_subsys_on_dfl(io_cgrp_subsys)) > > cgroup_rstat_updated(bio->bi_blkg->blkcg->css.cgroup, cpu); > > - put_cpu(); > > + put_cpu_light(); > > } > > Are you sure patch and backtrace match? There is also > u64_stats_update_begin_irqsave() which disables preemption on RT. So by > doing what you are suggesting, you only avoid disabling preemption in > cgroup_rstat_updated() which acquires a raw_spinlock_t. > You're right. I double-checked and noticed my tree didn't have the call to u64_stats_update_begin_irqsave. Only patch 2 is necessary indeed. > Sebastian >
