This patch (as1519) fixes a bug in the block layer's disk-events
polling. The polling is done by a work routine queued on the
system_nrt_wq workqueue. Since that workqueue isn't freezable, the
polling continues even in the middle of a system sleep transition.
Obviously, polling a suspended drive for media changes and such isn't
a good thing to do; in the case of USB mass-storage devices it can
lead to real problems requiring device resets and even re-enumeration.
The patch fixes things by creating a new system-wide, non-reentrant,
freezable workqueue and using it for disk-events polling.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
CC: Tejun Heo <tj@xxxxxxxxxx>
CC: <stable@xxxxxxxxxx>
---
I'm not sure who to send this patch to, since it is relevant to both
the block and PM subsystems. Jens, is it okay if Rafael takes it?
block/genhd.c | 10 +++++-----
include/linux/workqueue.h | 4 ++++
kernel/workqueue.c | 7 ++++++-
3 files changed, 15 insertions(+), 6 deletions(-)
Index: usb-3.3/block/genhd.c
===================================================================
--- usb-3.3.orig/block/genhd.c
+++ usb-3.3/block/genhd.c
@@ -1475,9 +1475,9 @@ static void __disk_unblock_events(struct
intv = disk_events_poll_jiffies(disk);
set_timer_slack(&ev->dwork.timer, intv / 4);
if (check_now)
- queue_delayed_work(system_nrt_wq, &ev->dwork, 0);
+ queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, 0);
else if (intv)
- queue_delayed_work(system_nrt_wq, &ev->dwork, intv);
+ queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, intv);
out_unlock:
spin_unlock_irqrestore(&ev->lock, flags);
}
@@ -1521,7 +1521,7 @@ void disk_flush_events(struct gendisk *d
ev->clearing |= mask;
if (!ev->block) {
cancel_delayed_work(&ev->dwork);
- queue_delayed_work(system_nrt_wq, &ev->dwork, 0);
+ queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, 0);
}
spin_unlock_irq(&ev->lock);
}
@@ -1558,7 +1558,7 @@ unsigned int disk_clear_events(struct ge
/* uncondtionally schedule event check and wait for it to finish */
disk_block_events(disk);
- queue_delayed_work(system_nrt_wq, &ev->dwork, 0);
+ queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, 0);
flush_delayed_work(&ev->dwork);
__disk_unblock_events(disk, false);
@@ -1595,7 +1595,7 @@ static void disk_events_workfn(struct wo
intv = disk_events_poll_jiffies(disk);
if (!ev->block && intv)
- queue_delayed_work(system_nrt_wq, &ev->dwork, intv);
+ queue_delayed_work(system_nrt_freezable_wq, &ev->dwork, intv);
spin_unlock_irq(&ev->lock);
Index: usb-3.3/include/linux/workqueue.h
===================================================================
--- usb-3.3.orig/include/linux/workqueue.h
+++ usb-3.3/include/linux/workqueue.h
@@ -289,12 +289,16 @@ enum {
*
* system_freezable_wq is equivalent to system_wq except that it's
* freezable.
+ *
+ * system_nrt_freezable_wq is equivalent to system_nrt_wq except that
+ * it's freezable.
*/
extern struct workqueue_struct *system_wq;
extern struct workqueue_struct *system_long_wq;
extern struct workqueue_struct *system_nrt_wq;
extern struct workqueue_struct *system_unbound_wq;
extern struct workqueue_struct *system_freezable_wq;
+extern struct workqueue_struct *system_nrt_freezable_wq;
extern struct workqueue_struct *
__alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
Index: usb-3.3/kernel/workqueue.c
===================================================================
--- usb-3.3.orig/kernel/workqueue.c
+++ usb-3.3/kernel/workqueue.c
@@ -253,11 +253,13 @@ struct workqueue_struct *system_long_wq
struct workqueue_struct *system_nrt_wq __read_mostly;
struct workqueue_struct *system_unbound_wq __read_mostly;
struct workqueue_struct *system_freezable_wq __read_mostly;
+struct workqueue_struct *system_nrt_freezable_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_wq);
EXPORT_SYMBOL_GPL(system_long_wq);
EXPORT_SYMBOL_GPL(system_nrt_wq);
EXPORT_SYMBOL_GPL(system_unbound_wq);
EXPORT_SYMBOL_GPL(system_freezable_wq);
+EXPORT_SYMBOL_GPL(system_nrt_freezable_wq);
#define CREATE_TRACE_POINTS
#include <trace/events/workqueue.h>
@@ -3833,8 +3835,11 @@ static int __init init_workqueues(void)
WQ_UNBOUND_MAX_ACTIVE);
system_freezable_wq = alloc_workqueue("events_freezable",
WQ_FREEZABLE, 0);
+ system_nrt_freezable_wq = alloc_workqueue("events_nrt_freezable",
+ WQ_NON_REENTRANT | WQ_FREEZABLE, 0);
BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
- !system_unbound_wq || !system_freezable_wq);
+ !system_unbound_wq || !system_freezable_wq ||
+ !system_nrt_freezable_wq);
return 0;
}
early_initcall(init_workqueues);
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