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[SCSI] sd: call blk_pm_runtime_init before add_disk
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> Cc: stable@vger.kernel.org Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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@ -2854,6 +2854,7 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
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gd->events |= DISK_EVENT_MEDIA_CHANGE;
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}
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blk_pm_runtime_init(sdp->request_queue, dev);
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add_disk(gd);
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if (sdkp->capacity)
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sd_dif_config_host(sdkp);
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@ -2862,7 +2863,6 @@ static void sd_probe_async(void *data, async_cookie_t cookie)
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sd_printk(KERN_NOTICE, sdkp, "Attached SCSI %sdisk\n",
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sdp->removable ? "removable " : "");
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blk_pm_runtime_init(sdp->request_queue, dev);
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scsi_autopm_put_device(sdp);
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put_device(&sdkp->dev);
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}
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