[PATCH 2.6][REPOST] Missing _raw_write_trylock for PPC/SMP

[Kyle Moffett]

I just implemented _raw_write_trylock for PPC32  There are probably 
bugs in it as
I'm a little rusty on my PPC assembly.  It needs someone skilled in PPC 
asm to look
at it, but hopefully it will work.  It compiles, but nothing currently 
in the kernel proper
uses it aside from write_trylock which is also currently unused.

Cheers,
Kyle Moffett


--- linux-2.6.6/include/asm-ppc/spinlock.h	2004-05-09 
22:32:28.000000000 -0400
+++ linux/include/asm-ppc/spinlock.h	2004-05-20 20:12:44.000000000 -0400
@@ -135,6 +135,28 @@
 	: "cr0", "memory");
 }

+static __inline__ int _raw_write_trylock(rwlock_t *rw)
+{
+	unsigned int tmp;
+	unsigned int ret;
+	
+	__asm__ __volatile__(
+"1:     lwarx           %0,0,%2         # write_trylock\n\
+	cmpwi           0,%0,0\n\
+	li              %1,0\n\
+	bne-            2f\n"
+	PPC405_ERR77(0,%1)
+"       stwcx.          %3,0,%2\n\
+	bne-            1b\n\
+	li              %1,1\n\
+	isync\n\
+2:"     : "=&r"(tmp), "=&r"(ret)
+	: "r"(&rw->lock), "r"(-1)
+	: "cr0", "memory");
+	
+	return ret;
+}
+
 static __inline__ void _raw_write_lock(rwlock_t *rw)
 {
 	unsigned int tmp;

Cheers,
Kyle Moffett

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