On 10/30/12 06:40, Zhuang, Jin Can wrote:
> Yes. Here's the warning.
> For the trace below, I used scsi_device_get/scsi_device_put() in scsi_run_queue(). (A little different from your patch). But I think it's the same.
>
> 10-23 18:15:53.309 8 8 I KERNEL : [ 268.994556] BUG: sleeping function called from invalid context at linux-2.6/kernel/workqueue.c:2500
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.006898] in_atomic(): 0, irqs_disabled(): 1, pid: 8, name: kworker/0:1
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.013689] Pid: 8, comm: kworker/0:1 Tainted: G WC 3.0.34-140359-g85a6d67-dirty #43
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.022113] Call Trace:
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.028828] [<c123464a>] __might_sleep+0x10a/0x110
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.033695] [<c12628a3>] wait_on_work+0x23/0x1a0
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.054913] [<c126472a>] __cancel_work_timer+0x6a/0x110
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.060217] [<c12647ff>] cancel_work_sync+0xf/0x20
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.065087] [<c1548d5d>] scsi_device_dev_release_usercontext+0x6d/0x100
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.071785] [<c12626a2>] execute_in_process_context+0x42/0x50
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.077609] [<c1548cc8>] scsi_device_dev_release+0x18/0x20
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.083174] [<c15234a0>] device_release+0x20/0x80
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.092479] [<c148d1b4>] kobject_release+0x84/0x1f0
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.107430] [<c148e8ec>] kref_put+0x2c/0x60
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.111688] [<c148d06d>] kobject_put+0x1d/0x50
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.116209] [<c15232a4>] put_device+0x14/0x20
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.120646] [<c153daa7>] scsi_device_put+0x37/0x60
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.125515] [<c1543cc7>] scsi_run_queue+0x247/0x320
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.130470] [<c1545903>] scsi_requeue_run_queue+0x13/0x20
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.135941] [<c1263efe>] process_one_work+0xfe/0x3f0
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.146384] [<c12644f1>] worker_thread+0x121/0x2f0
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.156383] [<c1267ffd>] kthread+0x6d/0x80
> 10-23 18:15:53.309 8 8 I KERNEL : [ 269.166124] [<c186a27a>] kernel_thread_helper+0x6/0x10
Thanks for the feedback. Something that kept me busy since I posted
the patch at the start of this thread is how to avoid adding two
atomic operations in a hot path (the get_device() and put_device()
calls in scsi_run_queue()). The patch below should realize that.
However, since I haven't been able so far to trigger the above call
trace that means that the test I ran wasn't sufficient to trigger
all code paths. So it would be appreciated if anyone could help
testing the patch below.
[PATCH] Fix race between starved list processing and device removal
---
block/blk-core.c | 9 +++++----
drivers/scsi/scsi_lib.c | 20 ++++++++++++++------
drivers/scsi/scsi_sysfs.c | 9 ++++++++-
3 files changed, 27 insertions(+), 11 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index e4f4e06..565484f 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -407,10 +407,11 @@ static void __blk_drain_queue(struct request_queue *q, bool drain_all)
/*
* This function might be called on a queue which failed
- * driver init after queue creation or is not yet fully
- * active yet. Some drivers (e.g. fd and loop) get unhappy
- * in such cases. Kick queue iff dispatch queue has
- * something on it and @q has request_fn set.
+ * driver init after queue creation, is not yet fully active
+ * or is being cleaned up and doesn't make progress anymore
+ * (e.g. a SCSI device in state SDEV_DEL). Kick queue iff
+ * dispatch queue has something on it and @q has request_fn
+ * set.
*/
if (!list_empty(&q->queue_head) && q->request_fn)
__blk_run_queue(q);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 488035b..1763181 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -447,8 +447,9 @@ static void scsi_run_queue(struct request_queue *q)
struct scsi_device, starved_entry);
list_del_init(&sdev->starved_entry);
if (scsi_target_is_busy(scsi_target(sdev))) {
- list_move_tail(&sdev->starved_entry,
- &shost->starved_list);
+ if (sdev->sdev_state != SDEV_DEL)
+ list_add_tail(&sdev->starved_entry,
+ &shost->starved_list);
continue;
}
@@ -1344,7 +1345,9 @@ static inline int scsi_target_queue_ready(struct Scsi_Host *shost,
}
if (scsi_target_is_busy(starget)) {
- list_move_tail(&sdev->starved_entry, &shost->starved_list);
+ if (sdev->sdev_state != SDEV_DEL)
+ list_move_tail(&sdev->starved_entry,
+ &shost->starved_list);
return 0;
}
@@ -1377,8 +1380,11 @@ static inline int scsi_host_queue_ready(struct request_queue *q,
}
}
if (scsi_host_is_busy(shost)) {
- if (list_empty(&sdev->starved_entry))
- list_add_tail(&sdev->starved_entry, &shost->starved_list);
+ if (list_empty(&sdev->starved_entry) &&
+ sdev->sdev_state != SDEV_DEL) {
+ list_add_tail(&sdev->starved_entry,
+ &shost->starved_list);
+ }
return 0;
}
@@ -1571,9 +1577,11 @@ static void scsi_request_fn(struct request_queue *q)
* a run when a tag is freed.
*/
if (blk_queue_tagged(q) && !blk_rq_tagged(req)) {
- if (list_empty(&sdev->starved_entry))
+ if (list_empty(&sdev->starved_entry) &&
+ sdev->sdev_state != SDEV_DEL) {
list_add_tail(&sdev->starved_entry,
&shost->starved_list);
+ }
goto not_ready;
}
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index ce5224c..2f0f31e 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)
@@ -973,7 +974,13 @@ void __scsi_remove_device(struct scsi_device *sdev)
* scsi_run_queue() invocations have finished before tearing down the
* device.
*/
+
scsi_device_set_state(sdev, SDEV_DEL);
+
+ spin_lock_irqsave(shost->host_lock, flags);
+ list_del(&sdev->starved_entry);
+ spin_unlock_irqrestore(shost->host_lock, flags);
+
blk_cleanup_queue(sdev->request_queue);
cancel_work_sync(&sdev->requeue_work);
--
1.7.10.4
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