From: Boy Wu <boy.wu@xxxxxxxxxxxx> In 32bit SMP systems, if multiple CPUs call blkcg_print_stat, which may cause blkcg_fill_root_iostats to have a concurrent problem on the seqlock in u64_stats_update, which will cause a deadlock on u64_stats_fetch_begin in blkcg_print_one_stat. Thus use blkg_stat_lock to replace u64_sync. Fixes: ef45fe470e1e ("blk-cgroup: show global disk stats in root cgroup io.stat") Signed-off-by: Boy Wu <boy.wu@xxxxxxxxxxxx> --- Change in v2: - update commit message - Remove u64_sync - Replace spin_lock_irq with guard statement - Replace blkg->q->queue_lock with blkg_stat_lock --- block/blk-cgroup.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 85b3b9051455..18b47ee1a640 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -952,7 +952,6 @@ static void blkcg_fill_root_iostats(void) struct blkcg_gq *blkg = bdev->bd_disk->queue->root_blkg; struct blkg_iostat tmp; int cpu; - unsigned long flags; memset(&tmp, 0, sizeof(tmp)); for_each_possible_cpu(cpu) { @@ -974,9 +973,10 @@ static void blkcg_fill_root_iostats(void) cpu_dkstats->sectors[STAT_DISCARD] << 9; } - flags = u64_stats_update_begin_irqsave(&blkg->iostat.sync); +#if BITS_PER_LONG == 32 + guard(raw_spinlock_irqsave)(&blkg_stat_lock); +#endif blkg_iostat_set(&blkg->iostat.cur, &tmp); - u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags); } } -- 2.18.0