Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 40 insertions, 0 deletions

diff --git a/arch/i386/lib/dec_and_lock.c b/arch/i386/lib/dec_and_lock.c
new file mode 100644
index 000000000000..ab43394dc775
--- /dev/null
+++ b/arch/i386/lib/dec_and_lock.c
@@ -0,0 +1,40 @@
+/*
+ * x86 version of "atomic_dec_and_lock()" using
+ * the atomic "cmpxchg" instruction.
+ *
+ * (For CPU's lacking cmpxchg, we use the slow
+ * generic version, and this one never even gets
+ * compiled).
+ */
+
+#include <linux/spinlock.h>
+#include <asm/atomic.h>
+
+int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
+{
+        int counter;
+        int newcount;
+
+repeat:
+        counter = atomic_read(atomic);
+        newcount = counter-1;
+
+        if (!newcount)
+                goto slow_path;
+
+        asm volatile("lock; cmpxchgl %1,%2"
+                :"=a" (newcount)
+                :"r" (newcount), "m" (atomic->counter), "0" (counter));
+
+        /* If the above failed, "eax" will have changed */
+        if (newcount != counter)
+                goto repeat;
+        return 0;
+
+slow_path:
+        spin_lock(lock);
+        if (atomic_dec_and_test(atomic))
+                return 1;
+        spin_unlock(lock);
+        return 0;
+}