workqueue: prepare for WQ_UNBOUND implementation

In preparation of WQ_UNBOUND addition, make the following changes.

* Add WORK_CPU_* constants for pseudo cpu id numbers used (currently
  only WORK_CPU_NONE) and use them instead of NR_CPUS.  This is to
  allow another pseudo cpu id for unbound cpu.

* Reorder WQ_* flags.

* Make workqueue_struct->cpu_wq a union which contains a percpu
  pointer, regular pointer and an unsigned long value and use
  kzalloc/kfree() in UP allocation path.  This will be used to
  implement unbound workqueues which will use only one cwq on SMPs.

* Move alloc_cwqs() allocation after initialization of wq fields, so
  that alloc_cwqs() has access to wq->flags.

* Trivial relocation of wq local variables in freeze functions.

These changes don't cause any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 3f36d37ac5b..139069a6286 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -50,6 +50,10 @@ enum {
         WORK_NR_COLORS          = (1 << WORK_STRUCT_COLOR_BITS) - 1,
         WORK_NO_COLOR           = WORK_NR_COLORS,
 
+        /* special cpu IDs */
+        WORK_CPU_NONE           = NR_CPUS,
+        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
@@ -60,7 +64,7 @@ enum {
 
         WORK_STRUCT_FLAG_MASK   = (1UL << WORK_STRUCT_FLAG_BITS) - 1,
         WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
-        WORK_STRUCT_NO_CPU      = NR_CPUS << WORK_STRUCT_FLAG_BITS,
+        WORK_STRUCT_NO_CPU      = WORK_CPU_NONE << WORK_STRUCT_FLAG_BITS,
 
         /* bit mask for work_busy() return values */
         WORK_BUSY_PENDING       = 1 << 0,
@@ -227,9 +231,9 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
         clear_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))
 
 enum {
-        WQ_FREEZEABLE           = 1 << 0, /* freeze during suspend */
+        WQ_NON_REENTRANT        = 1 << 0, /* guarantee non-reentrance */
         WQ_SINGLE_CPU           = 1 << 1, /* only single cpu at a time */
-        WQ_NON_REENTRANT        = 1 << 2, /* guarantee non-reentrance */
+        WQ_FREEZEABLE           = 1 << 2, /* freeze during suspend */
         WQ_RESCUER              = 1 << 3, /* has an rescue worker */
         WQ_HIGHPRI              = 1 << 4, /* high priority */
         WQ_CPU_INTENSIVE        = 1 << 5, /* cpu instensive workqueue */