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| author | Vivek Goyal <vgoyal@redhat.com> | 2010-04-22 11:54:52 -0400 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2010-05-06 08:54:00 +0200 |
| commit | dcf097b247affd8b88ad410a92298590c5600f44 (patch) | |
| tree | d5394d82b06fa926c6e8d9b9f12c13249348e954 | |
| parent | 6a7cc883d6ad95bb89282fc04e917c16d2b5584f (diff) | |
| download | op-kernel-dev-dcf097b247affd8b88ad410a92298590c5600f44.zip op-kernel-dev-dcf097b247affd8b88ad410a92298590c5600f44.tar.gz | |
blk-cgroup: Fix RCU correctness warning in cfq_init_queue()
It is necessary to be in an RCU read-side critical section when invoking
css_id(), so this patch adds one to blkiocg_add_blkio_group(). This is
actually a false positive, because this is called at initialization time
and hence always refers to the root cgroup, which cannot go away.
[ 103.790505] ===================================================
[ 103.790509] [ INFO: suspicious rcu_dereference_check() usage. ]
[ 103.790511] ---------------------------------------------------
[ 103.790514] kernel/cgroup.c:4432 invoked rcu_dereference_check() without protection!
[ 103.790517]
[ 103.790517] other info that might help us debug this:
[ 103.790519]
[ 103.790521]
[ 103.790521] rcu_scheduler_active = 1, debug_locks = 1
[ 103.790524] 4 locks held by bash/4422:
[ 103.790526] #0: (&buffer->mutex){+.+.+.}, at: [<ffffffff8114befa>] sysfs_write_file+0x3c/0x144
[ 103.790537] #1: (s_active#102){.+.+.+}, at: [<ffffffff8114bfa5>] sysfs_write_file+0xe7/0x144
[ 103.790544] #2: (&q->sysfs_lock){+.+.+.}, at: [<ffffffff812263b1>] queue_attr_store+0x49/0x8f
[ 103.790552] #3: (&(&blkcg->lock)->rlock){......}, at: [<ffffffff8122e4db>] blkiocg_add_blkio_group+0x2b/0xad
[ 103.790560]
[ 103.790561] stack backtrace:
[ 103.790564] Pid: 4422, comm: bash Not tainted 2.6.34-rc4-blkio-second-crash #81
[ 103.790567] Call Trace:
[ 103.790572] [<ffffffff81068f57>] lockdep_rcu_dereference+0x9d/0xa5
[ 103.790577] [<ffffffff8107fac1>] css_id+0x44/0x57
[ 103.790581] [<ffffffff8122e503>] blkiocg_add_blkio_group+0x53/0xad
[ 103.790586] [<ffffffff81231936>] cfq_init_queue+0x139/0x32c
[ 103.790591] [<ffffffff8121f2d0>] elv_iosched_store+0xbf/0x1bf
[ 103.790595] [<ffffffff812263d8>] queue_attr_store+0x70/0x8f
[ 103.790599] [<ffffffff8114bfa5>] ? sysfs_write_file+0xe7/0x144
[ 103.790603] [<ffffffff8114bfc6>] sysfs_write_file+0x108/0x144
[ 103.790609] [<ffffffff810f527f>] vfs_write+0xae/0x10b
[ 103.790612] [<ffffffff81069863>] ? trace_hardirqs_on_caller+0x10c/0x130
[ 103.790616] [<ffffffff810f539c>] sys_write+0x4a/0x6e
[ 103.790622] [<ffffffff81002b5b>] system_call_fastpath+0x16/0x1b
[ 103.790625]
Located-by: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| -rw-r--r-- | block/cfq-iosched.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 838834b..5f127cf 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -3694,8 +3694,10 @@ static void *cfq_init_queue(struct request_queue *q) * to make sure that cfq_put_cfqg() does not try to kfree root group */ atomic_set(&cfqg->ref, 1); + rcu_read_lock(); blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd, 0); + rcu_read_unlock(); #endif /* * Not strictly needed (since RB_ROOT just clears the node and we |
