wait: add wait_event_cmd()

Add a new API wait_event_cmd(). It's a variant of wait_even() with two
commands executed. One is executed before sleep, another after sleep.

Modified to match use wait.h approach based on suggestion by
Peter Zijlstra <peterz@infradead.org> - neilb

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 61939ba30aa0abdbe7e36e608343338c80fada6b..eaa00b10abaaa53cf441170841c3faec588e9de0 100644 (file)
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -278,6 +278,31 @@ do {                                                                       \
        __ret;                                                          \
 })
 
+#define __wait_event_cmd(wq, condition, cmd1, cmd2)                    \
+       (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,  \
+                           cmd1; schedule(); cmd2)
+
+/**
+ * wait_event_cmd - sleep until a condition gets true
+ * @wq: the waitqueue to wait on
+ * @condition: a C expression for the event to wait for
+ * cmd1: the command will be executed before sleep
+ * cmd2: the command will be executed after sleep
+ *
+ * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
+ * @condition evaluates to true. The @condition is checked each time
+ * the waitqueue @wq is woken up.
+ *
+ * wake_up() has to be called after changing any variable that could
+ * change the result of the wait condition.
+ */
+#define wait_event_cmd(wq, condition, cmd1, cmd2)                      \
+do {                                                                   \
+       if (condition)                                                  \
+               break;                                                  \
+       __wait_event_cmd(wq, condition, cmd1, cmd2);                    \
+} while (0)
+
 #define __wait_event_interruptible(wq, condition)                      \
        ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,          \
                      schedule())