Commit 90d3839b authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

block: Use u64_stats_init() to initialize seqcounts 



Now that seqcounts are lockdep enabled objects, we need to explicitly
initialize runtime allocated seqcounts so that lockdep can track them.

Without this patch, Fengguang was seeing:

  [    4.127282] INFO: trying to register non-static key.
  [    4.128027] the code is fine but needs lockdep annotation.
  [    4.128027] turning off the locking correctness validator.
  [    4.128027] CPU: 0 PID: 96 Comm: kworker/u4:1 Not tainted 3.12.0-next-20131108-10601-gbad570d #2
  [    4.128027] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
  [    ...     ]
  [    4.128027] Call Trace:
  [    4.128027]  [<7908e744>] ? console_unlock+0x353/0x380
  [    4.128027]  [<79dc7cf2>] dump_stack+0x48/0x60
  [    4.128027]  [<7908953e>] __lock_acquire.isra.26+0x7e3/0xceb
  [    4.128027]  [<7908a1c5>] lock_acquire+0x71/0x9a
  [    4.128027]  [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
  [    4.128027]  [<7940658b>] throtl_update_dispatch_stats+0x7c/0x153
  [    4.128027]  [<794079aa>] ? blk_throtl_bio+0x1c3/0x485
  [    4.128027]  [<794079aa>] blk_throtl_bio+0x1c3/0x485
  ...

Use u64_stats_init() for all affected data structures, which initializes
the seqcount.

Reported-and-Tested-by: default avatarFengguang Wu <fengguang.wu@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
[ Folded in another fix from the mailing list as well as a fix to that fix. Tweaked commit message. ]
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1384314134-6895-1-git-send-email-john.stultz@linaro.org


[ So I actually think that the two SOBs from PeterZ are the right depiction of the patch route. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 5216d530

block/blk-cgroup.h

+10 −0
Original line number Diff line number Diff line
@@ -402,6 +402,11 @@ struct request_list *__blk_queue_next_rl(struct request_list *rl, 
#define blk_queue_for_each_rl(rl, q)	\

	for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q)))



static inline void blkg_stat_init(struct blkg_stat *stat)

{

	u64_stats_init(&stat->syncp);

}



/**

 * blkg_stat_add - add a value to a blkg_stat

 * @stat: target blkg_stat
@@ -458,6 +463,11 @@ static inline void blkg_stat_merge(struct blkg_stat *to, struct blkg_stat *from) 
	blkg_stat_add(to, blkg_stat_read(from));

}



static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat)

{

	u64_stats_init(&rwstat->syncp);

}



/**

 * blkg_rwstat_add - add a value to a blkg_rwstat

 * @rwstat: target blkg_rwstat

block/blk-throttle.c

+10 −0
Original line number Diff line number Diff line
@@ -256,6 +256,12 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq) 
	}								\

} while (0)



static void tg_stats_init(struct tg_stats_cpu *tg_stats)

{

	blkg_rwstat_init(&tg_stats->service_bytes);

	blkg_rwstat_init(&tg_stats->serviced);

}



/*

 * Worker for allocating per cpu stat for tgs. This is scheduled on the

 * system_wq once there are some groups on the alloc_list waiting for
@@ -269,12 +275,16 @@ static void tg_stats_alloc_fn(struct work_struct *work) 


alloc_stats:

	if (!stats_cpu) {

		int cpu;



		stats_cpu = alloc_percpu(struct tg_stats_cpu);

		if (!stats_cpu) {

			/* allocation failed, try again after some time */

			schedule_delayed_work(dwork, msecs_to_jiffies(10));

			return;

		}

		for_each_possible_cpu(cpu)

			tg_stats_init(per_cpu_ptr(stats_cpu, cpu));

	}



	spin_lock_irq(&tg_stats_alloc_lock);

block/cfq-iosched.c

+25 −0
Original line number Diff line number Diff line
@@ -1508,6 +1508,29 @@ static void cfq_init_cfqg_base(struct cfq_group *cfqg) 
}



#ifdef CONFIG_CFQ_GROUP_IOSCHED

static void cfqg_stats_init(struct cfqg_stats *stats)

{

	blkg_rwstat_init(&stats->service_bytes);

	blkg_rwstat_init(&stats->serviced);

	blkg_rwstat_init(&stats->merged);

	blkg_rwstat_init(&stats->service_time);

	blkg_rwstat_init(&stats->wait_time);

	blkg_rwstat_init(&stats->queued);



	blkg_stat_init(&stats->sectors);

	blkg_stat_init(&stats->time);



#ifdef CONFIG_DEBUG_BLK_CGROUP

	blkg_stat_init(&stats->unaccounted_time);

	blkg_stat_init(&stats->avg_queue_size_sum);

	blkg_stat_init(&stats->avg_queue_size_samples);

	blkg_stat_init(&stats->dequeue);

	blkg_stat_init(&stats->group_wait_time);

	blkg_stat_init(&stats->idle_time);

	blkg_stat_init(&stats->empty_time);

#endif

}



static void cfq_pd_init(struct blkcg_gq *blkg)

{

	struct cfq_group *cfqg = blkg_to_cfqg(blkg);
@@ -1515,6 +1538,8 @@ static void cfq_pd_init(struct blkcg_gq *blkg) 
	cfq_init_cfqg_base(cfqg);

	cfqg->weight = blkg->blkcg->cfq_weight;

	cfqg->leaf_weight = blkg->blkcg->cfq_leaf_weight;

	cfqg_stats_init(&cfqg->stats);

	cfqg_stats_init(&cfqg->dead_stats);

}



static void cfq_pd_offline(struct blkcg_gq *blkg)

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