I recently ran into the same issue The test I did is plug/unplug u-disk in an interval of 1 second. And I found when sdev1 is being removed, scsi_run_queue is triggered by sdev2, which then accesses all the starving scsi device including sdev1. I have adopted the solution below which works fine for me so far. But there's one thing to fix in the patch below. When it put_device in scsi_run_queue, irq is disabled. As put_device may get into sleep, irq should be enabled before it's called. So I change it to: spin_unlock_irq(sdev->request_queue->queue_lock); put_device(&sdev->sdev_gendev); spin_lock_irq(shost->host_lock); -Jincan -----Original Message----- From: linux-scsi-owner@xxxxxxxxxxxxxxx [mailto:linux-scsi-owner@xxxxxxxxxxxxxxx] On Behalf Of Bart Van Assche Sent: Friday, October 26, 2012 8:05 PM To: linux-scsi Cc: James Bottomley; Mike Christie; Jens Axboe; Tejun Heo; Chanho Min Subject: [PATCH 6/7] Fix race between starved list processing and device removal The SCSI core maintains a "starved list" per SCSI host. This is a list of devices for which one or more requests have been queued but that have not yet been passed to the SCSI LLD. The function scsi_run_queue() examines all SCSI devices on the starved list. Since scsi_remove_device() can be invoked concurrently with scsi_run_queue() it is important to avoid that a SCSI device is accessed by that function after it has been freed. Avoid that the sdev reference count can drop to zero before the queue is run by scsi_run_queue() by inserting a get_device() / put_device() pair in that function. Move the code for removing a device from the starved list from scsi_device_dev_release_usercontext() to __scsi_remove_device() such that it is guaranteed that the newly added get_device() call succeeds. Reported-and-tested-by: Chanho Min <chanho.min@xxxxxxx> Reference: http://lkml.org/lkml/2012/8/2/96 Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Reviewed-by: Mike Christie <michaelc@xxxxxxxxxxx> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx> --- drivers/scsi/scsi_lib.c | 5 +++++ drivers/scsi/scsi_sysfs.c | 7 ++++++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index f29a1a9..c5d4ec2 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -452,10 +452,15 @@ static void scsi_run_queue(struct request_queue *q) continue; } + get_device(&sdev->sdev_gendev); spin_unlock(shost->host_lock); + spin_lock(sdev->request_queue->queue_lock); __blk_run_queue(sdev->request_queue); spin_unlock(sdev->request_queue->queue_lock); + + put_device(&sdev->sdev_gendev); + spin_lock(shost->host_lock); } /* put any unprocessed entries back */ diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index ce5224c..2661a957 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -348,7 +348,6 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work) starget->reap_ref++; list_del(&sdev->siblings); list_del(&sdev->same_target_siblings); - list_del(&sdev->starved_entry); spin_unlock_irqrestore(sdev->host->host_lock, flags); cancel_work_sync(&sdev->event_work); @@ -956,6 +955,8 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev) void __scsi_remove_device(struct scsi_device *sdev) { struct device *dev = &sdev->sdev_gendev; + struct Scsi_Host *shost = sdev->host; + unsigned long flags; if (sdev->is_visible) { if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0) @@ -977,6 +978,10 @@ void __scsi_remove_device(struct scsi_device *sdev) blk_cleanup_queue(sdev->request_queue); cancel_work_sync(&sdev->requeue_work); + spin_lock_irqsave(shost->host_lock, flags); + list_del(&sdev->starved_entry); + spin_unlock_irqrestore(shost->host_lock, flags); + if (sdev->host->hostt->slave_destroy) sdev->host->hostt->slave_destroy(sdev); transport_destroy_device(dev); -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
