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authorAaron Lu <aaron.lu@intel.com>2013-10-10 13:22:36 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-11-13 12:05:31 +0900
commitda0d4136d107d926273c227fdeaf805159044f66 (patch)
treeb86fbd322e98edbdc8faaf4b1fe8a7f379926550 /drivers/scsi
parentd60241f65bdc363f1be2b099bd98ff13a96c1f0d (diff)
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>
Diffstat (limited to 'drivers/scsi')
-rw-r--r--drivers/scsi/sd.c2
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);
}