timer: Permit statically-declared work with deferrable timers

Currently, you have to just define a delayed_work uninitialised, and then
initialise it before first use.  That's a tad clumsy.  At risk of playing
mind-games with the compiler, fooling it into doing pointer arithmetic
with compile-time-constants, this lets clients properly initialise delayed
work with deferrable timers statically.

This patch was inspired by the issues which lead Artem Bityutskiy to
commit 8eab945c5616fc984 ("sunrpc: make the cache cleaner workqueue
deferrable").

Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Acked-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index f11100f96482..88238c15ec3e 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -127,12 +127,20 @@ struct execute_work {
         .timer = TIMER_INITIALIZER(NULL, 0, 0),                 \
         }
 
+#define __DEFERRED_WORK_INITIALIZER(n, f) {                     \
+        .work = __WORK_INITIALIZER((n).work, (f)),              \
+        .timer = TIMER_DEFERRED_INITIALIZER(NULL, 0, 0),        \
+        }
+
 #define DECLARE_WORK(n, f)                                      \
         struct work_struct n = __WORK_INITIALIZER(n, f)
 
 #define DECLARE_DELAYED_WORK(n, f)                              \
         struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f)
 
+#define DECLARE_DEFERRED_WORK(n, f)                             \
+        struct delayed_work n = __DEFERRED_WORK_INITIALIZER(n, f)
+
 /*
  * initialize a work item's function pointer
  */