From: olof@lixom•net (Olof Johansson)
To: paulus@samba•org
Cc: linuxppc-dev@ozlabs•org
Subject: [PATCH] powerpc: Don't use long for 32-bit temp variables in spin lock ops
Date: Thu, 7 Jun 2007 12:08:16 -0500 [thread overview]
Message-ID: <20070607170816.GA4273@lixom.net> (raw)
The spinlock ops have long as their return type (as well as for some
of the temporary types internally). All locks are 32-bit, so it makes
no sense to do 64-bit ops on them.
For example, this is how my compiler built _spin_lock() for me:
c0000000004b2050: li r0,0
c0000000004b2054: stb r0,460(r13)
c0000000004b2058: lwz r0,8(r13)
c0000000004b205c: lwarx r9,0,r3
c0000000004b2060: cmpwi r9,0
c0000000004b2064: bne- c0000000004b2078 <._spin_lock+0x28>
c0000000004b2068: stwcx. r0,0,r3
c0000000004b206c: nop
c0000000004b2070: bne+ c0000000004b205c <._spin_lock+0xc>
c0000000004b2074: isync
c0000000004b2078: cmpdi cr7,r9,0
c0000000004b207c: .long 0x4dfe0020
c0000000004b2080: mr r1,r1
c0000000004b2084: lwz r0,0(r3)
c0000000004b2088: cmpdi cr7,r0,0
c0000000004b208c: bne+ cr7,c0000000004b2080 <._spin_lock+0x30>
c0000000004b2090: mr r2,r2
c0000000004b2094: b c0000000004b2058 <._spin_lock+0x8>
Note the cmpdi at ..78 when r9 was loaded with lwarx.
Unfortunately I haven't found a way to get rid of the duplicate
comparison alltogether.
Signed-off-by: Olof Johansson <olof@lixom•net>
Index: 2.6.21/include/asm-powerpc/spinlock.h
===================================================================
--- 2.6.21.orig/include/asm-powerpc/spinlock.h
+++ 2.6.21/include/asm-powerpc/spinlock.h
@@ -53,9 +53,9 @@
* This returns the old value in the lock, so we succeeded
* in getting the lock if the return value is 0.
*/
-static __inline__ unsigned long __spin_trylock(raw_spinlock_t *lock)
+static __inline__ unsigned int __spin_trylock(raw_spinlock_t *lock)
{
- unsigned long tmp, token;
+ unsigned int tmp, token;
token = LOCK_TOKEN;
__asm__ __volatile__(
@@ -179,9 +179,9 @@ extern void __raw_spin_unlock_wait(raw_s
* This returns the old value in the lock + 1,
* so we got a read lock if the return value is > 0.
*/
-static long __inline__ __read_trylock(raw_rwlock_t *rw)
+static int __inline__ __read_trylock(raw_rwlock_t *rw)
{
- long tmp;
+ int tmp;
__asm__ __volatile__(
"1: lwarx %0,0,%1\n"
@@ -203,9 +203,9 @@ static long __inline__ __read_trylock(ra
* This returns the old value in the lock,
* so we got the write lock if the return value is 0.
*/
-static __inline__ long __write_trylock(raw_rwlock_t *rw)
+static __inline__ int __write_trylock(raw_rwlock_t *rw)
{
- long tmp, token;
+ int tmp, token;
token = WRLOCK_TOKEN;
__asm__ __volatile__(
@@ -263,7 +263,7 @@ static int __inline__ __raw_write_tryloc
static void __inline__ __raw_read_unlock(raw_rwlock_t *rw)
{
- long tmp;
+ int tmp;
__asm__ __volatile__(
"# read_unlock\n\t"
next reply other threads:[~2007-06-07 17:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-07 17:08 Olof Johansson [this message]
2007-06-13 4:33 ` [PATCH] powerpc: Don't use long for 32-bit temp variables in spin lock ops Paul Mackerras
2007-06-13 14:14 ` Olof Johansson
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