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workqueue: fix how cpu number is stored in work->data

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Once a work starts execution, its data contains the cpu number it was
on instead of pointing to cwq.  This is added by commit 7a22ad75
(workqueue: carry cpu number in work data once execution starts) to
reliably determine the work was last on even if the workqueue itself
was destroyed inbetween.

Whether data points to a cwq or contains a cpu number was
distinguished by comparing the value against PAGE_OFFSET.  The
assumption was that a cpu number should be below PAGE_OFFSET while a
pointer to cwq should be above it.  However, on architectures which
use separate address spaces for user and kernel spaces, this doesn't
hold as PAGE_OFFSET is zero.

Fix it by using an explicit flag, WORK_STRUCT_CWQ, to mark what the
data field contains.  If the flag is set, it's pointing to a cwq;
otherwise, it contains a cpu number.

Reported on s390 and microblaze during linux-next testing.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sachin Sant <sachinp@in.ibm.com>
Reported-by: Michal Simek <michal.simek@petalogix.com>
Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Tested-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Tested-by: Michal Simek <monstr@monstr.eu>
This commit is contained in:
Tejun Heo
2010-07-22 14:14:25 +02:00
parent f2e005aaff
commit e120153ddf
2 changed files with 21 additions and 29 deletions
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14
include/linux/workqueue.h
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@ -25,17 +25,19 @@ typedef void (*work_func_t)(struct work_struct *work);
enum {
WORK_STRUCT_PENDING_BIT = 0, /* work item is pending execution */
WORK_STRUCT_LINKED_BIT = 1, /* next work is linked to this one */
WORK_STRUCT_CWQ_BIT = 1, /* data points to cwq */
WORK_STRUCT_LINKED_BIT = 2, /* next work is linked to this one */
#ifdef CONFIG_DEBUG_OBJECTS_WORK
WORK_STRUCT_STATIC_BIT = 2, /* static initializer (debugobjects) */
WORK_STRUCT_COLOR_SHIFT = 3, /* color for workqueue flushing */
WORK_STRUCT_STATIC_BIT = 3, /* static initializer (debugobjects) */
WORK_STRUCT_COLOR_SHIFT = 4, /* color for workqueue flushing */
#else
WORK_STRUCT_COLOR_SHIFT = 2, /* color for workqueue flushing */
WORK_STRUCT_COLOR_SHIFT = 3, /* color for workqueue flushing */
#endif
WORK_STRUCT_COLOR_BITS = 4,
WORK_STRUCT_PENDING = 1 << WORK_STRUCT_PENDING_BIT,
WORK_STRUCT_CWQ = 1 << WORK_STRUCT_CWQ_BIT,
WORK_STRUCT_LINKED = 1 << WORK_STRUCT_LINKED_BIT,
#ifdef CONFIG_DEBUG_OBJECTS_WORK
WORK_STRUCT_STATIC = 1 << WORK_STRUCT_STATIC_BIT,
@ -56,8 +58,8 @@ enum {
WORK_CPU_LAST = WORK_CPU_NONE,
/*
* Reserve 6 bits off of cwq pointer w/ debugobjects turned
* off. This makes cwqs aligned to 64 bytes which isn't too
* Reserve 7 bits off of cwq pointer w/ debugobjects turned
* off. This makes cwqs aligned to 128 bytes which isn't too
* excessive while allowing 15 workqueue flush colors.
*/
WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT +