[PATCH v2] add function spin_event_timeout()

[Timur Tabi]

The function spin_event_timeout() takes a condition and timeout value
(in jiffies) as parameters.  It spins until either the condition is true
or the timeout expires.  It returns non-zero if the condition is true,
zero otherwise.

Signed-off-by: Timur Tabi <timur@xxxxxxxxxxxxx>
---

v2: changes based on feedback

 include/linux/delay.h |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/include/linux/delay.h b/include/linux/delay.h
index fd832c6..235ca25 100644
--- a/include/linux/delay.h
+++ b/include/linux/delay.h
@@ -51,4 +51,26 @@ static inline void ssleep(unsigned int seconds)
 	msleep(seconds * 1000);
 }
 
+/**
+ * spin_event_timeout - spin until a condition gets true or a timeout elapses
+ * @condition: a C expression for the event to wait for
+ * @timeout: timeout, in jiffies
+ *
+ * The process spins until the @condition evaluates to true or the @timeout
+ * elapses.
+ *
+ * The function returns non-zero if the @condition evaluated to true, or
+ * zero if the @timeout elapsed.  If both occurs (e.g. the loop was
+ * pre-empted and the @condition became true in the meantime, but when the
+ * loop resumed the @timeout had already elapsed), then non-zero will be
+ * returned.
+ */
+#define spin_event_timeout(condition, timeout)			\
+({								\
+	unsigned long __timeout = jiffies + (timeout);		\
+	while (!(condition) && time_before(jiffies, __timeout))	\
+		cpu_relax();					\
+	(condition);						\
+})
+
 #endif /* defined(_LINUX_DELAY_H) */
-- 
1.6.1.3

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