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| author | Tejun Heo <tj@kernel.org> | 2013-05-14 13:52:31 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2013-05-14 13:52:31 -0700 |
| commit | 2a4fd070ee8561d918a3776388331bb7e92ea59e (patch) | |
| tree | 53eb9c6df1ea0e02cb3f3442fb85f9e25a4691ed /block/blk-cgroup.h | |
| parent | db61367038dcd222476881cb09fd54661b3cd508 (diff) | |
| download | lwn-2a4fd070ee8561d918a3776388331bb7e92ea59e.tar.gz lwn-2a4fd070ee8561d918a3776388331bb7e92ea59e.zip | |
blkcg: move bulk of blkcg_gq release operations to the RCU callback
Currently, when the last reference of a blkcg_gq is put, all then
release operations sans the actual freeing happen directly in
blkg_put(). As blkg_put() may be called under queue_lock, all
pd_exit_fn()s may be too. This makes it impossible for pd_exit_fn()s
to use del_timer_sync() on timers which grab the queue_lock which is
an irq-safe lock due to the deadlock possibility described in the
comment on top of del_timer_sync().
This can be easily avoided by perfoming the release operations in the
RCU callback instead of directly from blkg_put(). This patch moves
the blkcg_gq release operations to the RCU callback.
As this leaves __blkg_release() with only call_rcu() invocation,
blkg_rcu_free() is renamed to __blkg_release_rcu(), exported and
call_rcu() invocation is now done directly from blkg_put() instead of
going through __blkg_release() which is removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Diffstat (limited to 'block/blk-cgroup.h')
| -rw-r--r-- | block/blk-cgroup.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index e15f731d2cdd..8056c03a3382 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -266,7 +266,7 @@ static inline void blkg_get(struct blkcg_gq *blkg) blkg->refcnt++; } -void __blkg_release(struct blkcg_gq *blkg); +void __blkg_release_rcu(struct rcu_head *rcu); /** * blkg_put - put a blkg reference @@ -279,7 +279,7 @@ static inline void blkg_put(struct blkcg_gq *blkg) lockdep_assert_held(blkg->q->queue_lock); WARN_ON_ONCE(blkg->refcnt <= 0); if (!--blkg->refcnt) - __blkg_release(blkg); + call_rcu(&blkg->rcu_head, __blkg_release_rcu); } struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q, |