Commit 53a42b63 authored by John David Anglin's avatar John David Anglin Committed by Helge Deller
Browse files

parisc: Switch to more fine grained lws locks 



Increase the number of lws locks to 256 entries (instead of 16) and
choose lock entry based on bits 3-11 (instead of 4-7) of the relevant
address.  With this change we archieve more fine-grained locking in
futex syscalls and thus reduce the number of possible stalls.

Signed-off-by: default avatarJohn David Anglin <dave.anglin@bell.net>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent 2a7d4eed

arch/parisc/include/asm/futex.h

+2 −2
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ 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 & 0x3f8) >> 1;

	arch_spinlock_t *s = (arch_spinlock_t *)&lws_lock_start[index];

	local_irq_save(*flags);

	arch_spin_lock(s);
@@ -26,7 +26,7 @@ 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 & 0x3f8) >> 1;

	arch_spinlock_t *s = (arch_spinlock_t *)&lws_lock_start[index];

	arch_spin_unlock(s);

	local_irq_restore(*flags);

arch/parisc/kernel/syscall.S

+5 −5
Original line number Diff line number Diff line
@@ -571,8 +571,8 @@ lws_compare_and_swap: 
	ldil	L%lws_lock_start, %r20

	ldo	R%lws_lock_start(%r20), %r28



	/* Extract four bits from r26 and hash lock (Bits 4-7) */

	extru  %r26, 27, 4, %r20

	/* Extract eight bits from r26 and hash lock (Bits 3-11) */

	extru  %r26, 28, 8, %r20



	/* Find lock to use, the hash is either one of 0 to

	   15, multiplied by 16 (keep it 16-byte aligned)
@@ -761,8 +761,8 @@ cas2_lock_start: 
	ldil	L%lws_lock_start, %r20

	ldo	R%lws_lock_start(%r20), %r28



	/* Extract four bits from r26 and hash lock (Bits 4-7) */

	extru  %r26, 27, 4, %r20

	/* Extract eight bits from r26 and hash lock (Bits 3-11) */

	extru  %r26, 28, 8, %r20



	/* Find lock to use, the hash is either one of 0 to

	   15, multiplied by 16 (keep it 16-byte aligned)
@@ -950,7 +950,7 @@ END(sys_call_table64) 
	.align	L1_CACHE_BYTES

ENTRY(lws_lock_start)

	/* lws locks */

	.rept 16

	.rept 256

	/* Keep locks aligned at 16-bytes */

	.word 1

	.word 0

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