diff options
author | Jianpeng Ma <majianpeng@gmail.com> | 2013-07-03 11:25:24 (GMT) |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2013-07-03 11:25:24 (GMT) |
commit | d50235b7bc3ee0a0427984d763ea7534149531b4 (patch) | |
tree | acf1916e7926c1a0dddbe08db11ca2426a3816cc /fs/block_dev.c | |
parent | a6b3f7614ca690e49e934c291f707b0c19312194 (diff) | |
download | linux-d50235b7bc3ee0a0427984d763ea7534149531b4.tar.xz |
elevator: Fix a race in elevator switching
There's a race between elevator switching and normal io operation.
Because the allocation of struct elevator_queue and struct elevator_data
don't in a atomic operation.So there are have chance to use NULL
->elevator_data.
For example:
Thread A: Thread B
blk_queu_bio elevator_switch
spin_lock_irq(q->queue_block) elevator_alloc
elv_merge elevator_init_fn
Because call elevator_alloc, it can't hold queue_lock and the
->elevator_data is NULL.So at the same time, threadA call elv_merge and
nedd some info of elevator_data.So the crash happened.
Move the elevator_alloc into func elevator_init_fn, it make the
operations in a atomic operation.
Using the follow method can easy reproduce this bug
1:dd if=/dev/sdb of=/dev/null
2:while true;do echo noop > scheduler;echo deadline > scheduler;done
The test method also use this method.
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs/block_dev.c')
0 files changed, 0 insertions, 0 deletions