Re: [PATCH] parisc: Align locks for LWS syscalls to L1 cache size

[Helge Deller <deller@gmx.de>]

parisc: Align locks for LWS syscalls to L1 cache size (v2)

Align the locks for the Light-weight-syscall (LWS) which are used
for atomic userspace operations (e.g. gcc atomic builtins) on L1 cache
boundaries. This should speed up LWS calls on PA20 systems.

Reported-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S
index 7ef22e3..80c2306 100644
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -561,9 +561,9 @@ lws_compare_and_swap:
 	extru  %r26, 27, 4, %r20
 
 	/* Find lock to use, the hash is either one of 0 to
-	   15, multiplied by 16 (keep it 16-byte aligned)
+	   15, multiplied by L1_CACHE_BYTES (keep it L1 cache aligned)
 	   and add to the lock table offset. */
-	shlw	%r20, 4, %r20
+	shlw	%r20, L1_CACHE_SHIFT, %r20
 	add	%r20, %r28, %r20
 
 # if ENABLE_LWS_DEBUG
@@ -751,9 +751,9 @@ cas2_lock_start:
 	extru  %r26, 27, 4, %r20
 
 	/* Find lock to use, the hash is either one of 0 to
-	   15, multiplied by 16 (keep it 16-byte aligned)
+	   15, multiplied by L1_CACHE_BYTES (keep it L1 cache aligned)
 	   and add to the lock table offset. */
-	shlw	%r20, 4, %r20
+	shlw	%r20, L1_CACHE_SHIFT, %r20
 	add	%r20, %r28, %r20
 
 	rsm	PSW_SM_I, %r0			/* Disable interrupts */
@@ -931,11 +931,9 @@ END(sys_call_table64)
 ENTRY(lws_lock_start)
 	/* lws locks */
 	.rept 16
-	/* Keep locks aligned at 16-bytes */
+	/* Keep locks aligned to L1_CACHE_BYTES */
 	.word 1
-	.word 0 
-	.word 0
-	.word 0
+	.align	L1_CACHE_BYTES
 	.endr
 END(lws_lock_start)
 	.previous


diff --git a/arch/parisc/include/asm/futex.h b/arch/parisc/include/asm/futex.h
index 49df148..47b075c 100644
--- a/arch/parisc/include/asm/futex.h
+++ b/arch/parisc/include/asm/futex.h
@@ -15,7 +15,7 @@ static inline void
 _futex_spin_lock_irqsave(u32 __user *uaddr, unsigned long int *flags)
 {
 	extern u32 lws_lock_start[];
-	long index = ((long)uaddr & 0xf0) >> 2;
+	long index = (((long)uaddr & 0xf0) >> 4) << (L1_CACHE_SHIFT-2);
 	arch_spinlock_t *s = (arch_spinlock_t *)&lws_lock_start[index];
 	local_irq_save(*flags);
 	arch_spin_lock(s);
@@ -25,7 +25,7 @@ static inline void
 _futex_spin_unlock_irqrestore(u32 __user *uaddr, unsigned long int *flags)
 {
 	extern u32 lws_lock_start[];
-	long index = ((long)uaddr & 0xf0) >> 2;
+	long index = (((long)uaddr & 0xf0) >> 4) << (L1_CACHE_SHIFT-2);
 	arch_spinlock_t *s = (arch_spinlock_t *)&lws_lock_start[index];
 	arch_spin_unlock(s);
 	local_irq_restore(*flags);