workqueue: introduce WORK_OFFQ_FLAG_*
Low WORK_STRUCT_FLAG_BITS bits of work_struct->data contain
WORK_STRUCT_FLAG_* and flush color. If the work item is queued, the
rest point to the cpu_workqueue with WORK_STRUCT_CWQ set; otherwise,
WORK_STRUCT_CWQ is clear and the bits contain the last CPU number -
either a real CPU number or one of WORK_CPU_*.
Scheduled addition of mod_delayed_work[_on]() requires an additional
flag, which is used only while a work item is off queue. There are
more than enough bits to represent off-queue CPU number on both 32 and
64bits. This patch introduces WORK_OFFQ_FLAG_* which occupy the lower
part of the @work->data high bits while off queue. This patch doesn't
define any actual OFFQ flag yet.
Off-queue CPU number is now shifted by WORK_OFFQ_CPU_SHIFT, which adds
the number of bits used by OFFQ flags to WORK_STRUCT_FLAG_SHIFT, to
make room for OFFQ flags.
To avoid shift width warning with large WORK_OFFQ_FLAG_BITS, ulong
cast is added to WORK_STRUCT_NO_CPU and, just in case, BUILD_BUG_ON()
to check that there are enough bits to accomodate off-queue CPU number
is added.
This patch doesn't make any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index ab95fef..f562674 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -68,9 +68,15 @@
WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT +
WORK_STRUCT_COLOR_BITS,
+ /* data contains off-queue information when !WORK_STRUCT_CWQ */
+ WORK_OFFQ_FLAG_BASE = WORK_STRUCT_FLAG_BITS,
+ WORK_OFFQ_FLAG_BITS = 0,
+ WORK_OFFQ_CPU_SHIFT = WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,
+
+ /* convenience constants */
WORK_STRUCT_FLAG_MASK = (1UL << WORK_STRUCT_FLAG_BITS) - 1,
WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
- WORK_STRUCT_NO_CPU = WORK_CPU_NONE << WORK_STRUCT_FLAG_BITS,
+ WORK_STRUCT_NO_CPU = (unsigned long)WORK_CPU_NONE << WORK_OFFQ_CPU_SHIFT,
/* bit mask for work_busy() return values */
WORK_BUSY_PENDING = 1 << 0,