blkcg: tg_stats_alloc_lock is an irq lock (ff26eaad) · Commits · 戴 / test

tg_stats_alloc_lock nests inside queue lock and should always be held with irq disabled. throtl_pd_{init|exit}() were using non-irqsafe spinlock ops which triggered inverse lock ordering via irq warning via RCU freeing of blkg invoking throtl_pd_exit() w/o disabling IRQ. Update both functions to use irq safe operations. Signed-off-by:

Tejun Heo <tj@kernel.org> Reported-by:

Sasha Levin <sasha.levin@oracle.com> LKML-Reference: <1335339396.16988.80.camel@lappy> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-throttle.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -219,6 +219,7 @@ alloc_stats:
		static void throtl_pd_init(struct blkcg_gq *blkg)
		{
		struct throtl_grp *tg = blkg_to_tg(blkg);
		unsigned long flags;

		RB_CLEAR_NODE(&tg->rb_node);
		bio_list_init(&tg->bio_lists[0]);
		@@ -235,19 +236,20 @@ static void throtl_pd_init(struct blkcg_gq *blkg)
		* but percpu allocator can't be called from IO path. Queue tg on
		* tg_stats_alloc_list and allocate from work item.
		*/
		spin_lock(&tg_stats_alloc_lock);
		spin_lock_irqsave(&tg_stats_alloc_lock, flags);
		list_add(&tg->stats_alloc_node, &tg_stats_alloc_list);
		queue_delayed_work(system_nrt_wq, &tg_stats_alloc_work, 0);
		spin_unlock(&tg_stats_alloc_lock);
		spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);
		}

		static void throtl_pd_exit(struct blkcg_gq *blkg)
		{
		struct throtl_grp *tg = blkg_to_tg(blkg);
		unsigned long flags;

		spin_lock(&tg_stats_alloc_lock);
		spin_lock_irqsave(&tg_stats_alloc_lock, flags);
		list_del_init(&tg->stats_alloc_node);
		spin_unlock(&tg_stats_alloc_lock);
		spin_unlock_irqrestore(&tg_stats_alloc_lock, flags);

		free_percpu(tg->stats_cpu);
		}

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