linux-kernel - [PATCH] add function spin_event

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Date:	Fri,  6 Mar 2009 18:13:21 -0600
From:	Timur Tabi <timur@...escale.com>
To:	linux-kernel@...r.kernel.org
Subject: [PATCH] add function spin_event_timeout()

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@...escale.com>
---
 include/linux/delay.h |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/include/linux/delay.h b/include/linux/delay.h
index fd832c6..00ac466 100644
--- a/include/linux/delay.h
+++ b/include/linux/delay.h
@@ -51,4 +51,25 @@ 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)		\
+({							\
+	long __timeout = jiffies + (timeout);		\
+	while (!(condition) && (jiffies < __timeout));	\
+	(condition);					\
+})
+
 #endif /* defined(_LINUX_DELAY_H) */
-- 
1.6.1.3

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