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| author | Aaron Lu <aaron.lu@intel.com> | 2013-10-10 13:22:36 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-11-13 12:05:31 +0900 |
| commit | da0d4136d107d926273c227fdeaf805159044f66 (patch) | |
| tree | b86fbd322e98edbdc8faaf4b1fe8a7f379926550 | |
| parent | d60241f65bdc363f1be2b099bd98ff13a96c1f0d (diff) | |
| download | linux-3.10-da0d4136d107d926273c227fdeaf805159044f66.tar.gz linux-3.10-da0d4136d107d926273c227fdeaf805159044f66.tar.bz2 linux-3.10-da0d4136d107d926273c227fdeaf805159044f66.zip | |
SCSI: sd: call blk_pm_runtime_init before add_disk
commit 10c580e4239df5c3344ca00322eca86ab2de880b upstream.
Sujit has found a race condition that would make q->nr_pending
unbalanced, it occurs as Sujit explained:
"
sd_probe_async() ->
add_disk() ->
disk_add_event() ->
schedule(disk_events_workfn)
sd_revalidate_disk()
blk_pm_runtime_init()
return;
Let's say the disk_events_workfn() calls sd_check_events() which tries
to send test_unit_ready() and because of sd_revalidate_disk() trying to
send another commands the test_unit_ready() might be re-queued as the
tagged command queuing is disabled.
So the race condition is -
Thread 1 | Thread 2
sd_revalidate_disk() | sd_check_events()
...nr_pending = 0 as q->dev = NULL| scsi_queue_insert()
blk_runtime_pm_init() | blk_pm_requeue_request() ->
| nr_pending = -1 since
| q->dev != NULL
"
The problem is, the test_unit_ready request doesn't get counted the
first time it is queued, so the later decrement of q->nr_pending in
blk_pm_requeue_request makes it unbalanced.
Fix this by calling blk_pm_runtime_init before add_disk so that all
requests initiated there will all be counted.
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Reported-and-tested-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/scsi/sd.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index c3986344133..734a29a70f6 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -2843,6 +2843,7 @@ static void sd_probe_async(void *data, async_cookie_t cookie) gd->events |= DISK_EVENT_MEDIA_CHANGE; } + blk_pm_runtime_init(sdp->request_queue, dev); add_disk(gd); if (sdkp->capacity) sd_dif_config_host(sdkp); @@ -2851,7 +2852,6 @@ static void sd_probe_async(void *data, async_cookie_t cookie) sd_printk(KERN_NOTICE, sdkp, "Attached SCSI %sdisk\n", sdp->removable ? "removable " : ""); - blk_pm_runtime_init(sdp->request_queue, dev); scsi_autopm_put_device(sdp); put_device(&sdkp->dev); } |