Block: use a freezable workqueue for disk-event polling
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@rowland.harvard.edu>
CC: <stable@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index bec7b5b..f2c5638 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -253,11 +253,13 @@
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 @@
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);