From: Samuel Thibault <samuel.thibault@eu.citrix.com>
Subject: [PATCH] [Mini-OS] add trydown
Date: Thu, 17 Jan 2008 13:47:47 +0000
Message-ID: <20080117134747.GE11129@implementation.uk.xensource.com>
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add trydown

Signed-off-by: Samuel Thibault <samuel.thibault@eu.citrix.com>

diff -r a66bdc82d8fa extras/mini-os/include/semaphore.h
--- a/extras/mini-os/include/semaphore.h	Wed Jan 16 11:44:41 2008 +0000
+++ b/extras/mini-os/include/semaphore.h	Thu Jan 17 12:29:01 2008 +0000
@@ -49,6 +49,19 @@ static inline void init_SEMAPHORE(struct
 
 #define init_MUTEX(sem) init_SEMAPHORE(sem, 1)
 
+static inline int trydown(struct semaphore *sem)
+{
+    unsigned long flags;
+    int ret = 0;
+    local_irq_save(flags);
+    if (sem->count > 0) {
+        ret = 1;
+        sem->count--;
+    }
+    local_irq_restore(flags);
+    return ret;
+}
+
 static void inline down(struct semaphore *sem)
 {
     unsigned long flags;