[Xen-changelog] [xen-unstable] [Mini-OS] Make semaphores callback-safe

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1195910799 0
# Node ID 9e88db95ddc7eedb687252b0ed8f73a21841e742
# Parent  0814fb0f8a4debac73c97a55affed02a07767bcc
[Mini-OS] Make semaphores callback-safe

One may want to use semaphores in event handlers to wake threads
waiting for a resource, so semaphores then need to be callback-safe.

Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxx>
---
 extras/mini-os/include/semaphore.h |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletion(-)

diff -r 0814fb0f8a4d -r 9e88db95ddc7 extras/mini-os/include/semaphore.h
--- a/extras/mini-os/include/semaphore.h        Sat Nov 24 13:23:22 2007 +0000
+++ b/extras/mini-os/include/semaphore.h        Sat Nov 24 13:26:39 2007 +0000
@@ -49,14 +49,25 @@ static inline void init_MUTEX(struct sem
 
 static void inline down(struct semaphore *sem)
 {
-    wait_event(sem->wait, sem->count > 0);
+    unsigned long flags;
+    while (1) {
+        wait_event(sem->wait, sem->count > 0);
+        local_irq_save(flags);
+        if (sem->count > 0)
+            break;
+        local_irq_restore(flags);
+    }
     sem->count--;
+    local_irq_restore(flags);
 }
 
 static void inline up(struct semaphore *sem)
 {
+    unsigned long flags;
+    local_irq_save(flags);
     sem->count++;
     wake_up(&sem->wait);
+    local_irq_restore(flags);
 }
 
 /* FIXME! Thre read/write semaphores are unimplemented! */

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