[patch 3/3] Directed yield: direct yield of spinlocks for s390.

From: Martin Schwidefsky
Date: Tue Sep 19 2006 - 07:20:53 EST

From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

[patch 3/3] Directed yield: direct yield of spinlocks for s390.

Use the new diagnose 0x9c in the spinlock implementation for s390.
It yields the remaining timeslice of the virtual cpu that tries to
acquire a lock to the virtual cpu that is the current holder of the
lock.

Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---

arch/s390/kernel/head31.S | 11 ++++++
arch/s390/kernel/head64.S | 11 ++++++
arch/s390/lib/spinlock.c | 62 +++++++++++++++++++++++---------------
include/asm-s390/setup.h | 1
include/asm-s390/spinlock.h | 31 +++++++++++++------
include/asm-s390/spinlock_types.h | 6 +--
6 files changed, 87 insertions(+), 35 deletions(-)

diff -urpN linux-2.6/arch/s390/kernel/head31.S linux-2.6-patched/arch/s390/kernel/head31.S
--- linux-2.6/arch/s390/kernel/head31.S 2006-09-19 12:59:13.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/head31.S 2006-09-19 12:59:36.000000000 +0200
@@ -254,6 +254,16 @@ startup_continue:
oi 3(%r12),0x80 # set IDTE flag
.Lchkidte:

+#
+# find out if the diag 0x9c is available
+#
+ mvc __LC_PGM_NEW_PSW(8),.Lpcdiag9c-.LPG1(%r13)
+ stap __LC_CPUID+4 # store cpu address
+ lh %r1,__LC_CPUID+4
+ diag %r1,0,0x9c # test diag 0x9c
+ oi 2(%r12),1 # set diag9c flag
+.Lchkdiag9c:
+
lpsw .Lentry-.LPG1(13) # jump to _stext in primary-space,
# virtual and never return ...
.align 8
@@ -281,6 +291,7 @@ startup_continue:
.Lpccsp:.long 0x00080000,0x80000000 + .Lchkcsp
.Lpcmvpg:.long 0x00080000,0x80000000 + .Lchkmvpg
.Lpcidte:.long 0x00080000,0x80000000 + .Lchkidte
+.Lpcdiag9c:.long 0x00080000,0x80000000 + .Lchkdiag9c
.Lmemsize:.long memory_size
.Lmchunk:.long memory_chunk
.Lmflags:.long machine_flags
diff -urpN linux-2.6/arch/s390/kernel/head64.S linux-2.6-patched/arch/s390/kernel/head64.S
--- linux-2.6/arch/s390/kernel/head64.S 2006-09-19 12:59:27.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/head64.S 2006-09-19 12:59:36.000000000 +0200
@@ -251,6 +251,17 @@ startup_continue:
0:

#
+# find out if the diag 0x9c is available
+#
+ la %r1,0f-.LPG1(%r13) # set program check address
+ stg %r1,__LC_PGM_NEW_PSW+8
+ stap __LC_CPUID+4 # store cpu address
+ lh %r1,__LC_CPUID+4
+ diag %r1,0,0x9c # test diag 0x9c
+ oi 6(%r12),1 # set diag9c flag
+0:
+
+#
# find out if we have the MVCOS instruction
#
la %r1,0f-.LPG1(%r13) # set program check address
diff -urpN linux-2.6/arch/s390/lib/spinlock.c linux-2.6-patched/arch/s390/lib/spinlock.c
--- linux-2.6/arch/s390/lib/spinlock.c 2006-06-18 03:49:35.000000000 +0200
+++ linux-2.6-patched/arch/s390/lib/spinlock.c 2006-09-19 12:59:36.000000000 +0200
@@ -24,57 +24,76 @@ static int __init spin_retry_setup(char
}
__setup("spin_retry=", spin_retry_setup);

-static inline void
-_diag44(void)
+static inline void _raw_yield(void)
{
-#ifdef CONFIG_64BIT
if (MACHINE_HAS_DIAG44)
-#endif
asm volatile("diag 0,0,0x44");
}

-void
-_raw_spin_lock_wait(raw_spinlock_t *lp, unsigned int pc)
+static inline void _raw_yield_cpu(int cpu)
+{
+ if (MACHINE_HAS_DIAG9C)
+ asm volatile("diag %0,0,0x9c"
+ : : "d" (__cpu_logical_map[cpu]));
+ else
+ _raw_yield();
+}
+
+void _raw_spin_lock_wait(raw_spinlock_t *lp, unsigned int pc)
{
int count = spin_retry;
+ unsigned int cpu = ~smp_processor_id();

while (1) {
if (count-- <= 0) {
- _diag44();
+ unsigned int owner = lp->owner_cpu;
+ if (owner != 0)
+ _raw_yield_cpu(~owner);
count = spin_retry;
}
if (__raw_spin_is_locked(lp))
continue;
- if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
+ if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0) {
+ lp->owner_pc = pc;
return;
+ }
}
}
EXPORT_SYMBOL(_raw_spin_lock_wait);

-int
-_raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc)
+int _raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc)
{
- int count = spin_retry;
+ unsigned int cpu = ~smp_processor_id();
+ int count;

- while (count-- > 0) {
+ for (count = spin_retry; count > 0; count--) {
if (__raw_spin_is_locked(lp))
continue;
- if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
+ if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0) {
+ lp->owner_pc = pc;
return 1;
+ }
}
return 0;
}
EXPORT_SYMBOL(_raw_spin_trylock_retry);

-void
-_raw_read_lock_wait(raw_rwlock_t *rw)
+void _raw_spin_relax(raw_spinlock_t *lock)
+{
+ unsigned int cpu = lock->owner_cpu;
+ if (cpu != 0)
+ _raw_yield_cpu(~cpu);
+}
+EXPORT_SYMBOL(_raw_spin_relax);
+
+void _raw_read_lock_wait(raw_rwlock_t *rw)
{
unsigned int old;
int count = spin_retry;

while (1) {
if (count-- <= 0) {
- _diag44();
+ _raw_yield();
count = spin_retry;
}
if (!__raw_read_can_lock(rw))
@@ -86,8 +105,7 @@ _raw_read_lock_wait(raw_rwlock_t *rw)
}
EXPORT_SYMBOL(_raw_read_lock_wait);

-int
-_raw_read_trylock_retry(raw_rwlock_t *rw)
+int _raw_read_trylock_retry(raw_rwlock_t *rw)
{
unsigned int old;
int count = spin_retry;
@@ -103,14 +121,13 @@ _raw_read_trylock_retry(raw_rwlock_t *rw
}
EXPORT_SYMBOL(_raw_read_trylock_retry);

-void
-_raw_write_lock_wait(raw_rwlock_t *rw)
+void _raw_write_lock_wait(raw_rwlock_t *rw)
{
int count = spin_retry;

while (1) {
if (count-- <= 0) {
- _diag44();
+ _raw_yield();
count = spin_retry;
}
if (!__raw_write_can_lock(rw))
@@ -121,8 +138,7 @@ _raw_write_lock_wait(raw_rwlock_t *rw)
}
EXPORT_SYMBOL(_raw_write_lock_wait);

-int
-_raw_write_trylock_retry(raw_rwlock_t *rw)
+int _raw_write_trylock_retry(raw_rwlock_t *rw)
{
int count = spin_retry;

diff -urpN linux-2.6/include/asm-s390/setup.h linux-2.6-patched/include/asm-s390/setup.h
--- linux-2.6/include/asm-s390/setup.h 2006-09-19 12:59:27.000000000 +0200
+++ linux-2.6-patched/include/asm-s390/setup.h 2006-09-19 12:59:36.000000000 +0200
@@ -39,6 +39,7 @@ extern unsigned long machine_flags;
#define MACHINE_IS_P390 (machine_flags & 4)
#define MACHINE_HAS_MVPG (machine_flags & 16)
#define MACHINE_HAS_IDTE (machine_flags & 128)
+#define MACHINE_HAS_DIAG9C (machine_flags & 256)

#ifndef __s390x__
#define MACHINE_HAS_IEEE (machine_flags & 2)
diff -urpN linux-2.6/include/asm-s390/spinlock.h linux-2.6-patched/include/asm-s390/spinlock.h
--- linux-2.6/include/asm-s390/spinlock.h 2006-09-19 12:59:35.000000000 +0200
+++ linux-2.6-patched/include/asm-s390/spinlock.h 2006-09-19 12:59:36.000000000 +0200
@@ -11,6 +11,8 @@
#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H

+#include <linux/smp.h>
+
static inline int
_raw_compare_and_swap(volatile unsigned int *lock,
unsigned int old, unsigned int new)
@@ -31,34 +33,46 @@ _raw_compare_and_swap(volatile unsigned
* (the type definitions are in asm/spinlock_types.h)
*/

-#define __raw_spin_is_locked(x) ((x)->lock != 0)
+#define __raw_spin_is_locked(x) ((x)->owner_cpu != 0)
#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
#define __raw_spin_unlock_wait(lock) \
- do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
+ do { while (__raw_spin_is_locked(lock)) \
+ _raw_spin_relax(lock); } while (0)

-extern void _raw_spin_lock_wait(raw_spinlock_t *lp, unsigned int pc);
-extern int _raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc);
+extern void _raw_spin_lock_wait(raw_spinlock_t *, unsigned int pc);
+extern int _raw_spin_trylock_retry(raw_spinlock_t *, unsigned int pc);
+extern void _raw_spin_relax(raw_spinlock_t *lock);

static inline void __raw_spin_lock(raw_spinlock_t *lp)
{
unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
+ int old;

- if (unlikely(_raw_compare_and_swap(&lp->lock, 0, pc) != 0))
- _raw_spin_lock_wait(lp, pc);
+ old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
+ if (likely(old == 0)) {
+ lp->owner_pc = pc;
+ return;
+ }
+ _raw_spin_lock_wait(lp, pc);
}

static inline int __raw_spin_trylock(raw_spinlock_t *lp)
{
unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
+ int old;

- if (likely(_raw_compare_and_swap(&lp->lock, 0, pc) == 0))
+ old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
+ if (likely(old == 0)) {
+ lp->owner_pc = pc;
return 1;
+ }
return _raw_spin_trylock_retry(lp, pc);
}

static inline void __raw_spin_unlock(raw_spinlock_t *lp)
{
- _raw_compare_and_swap(&lp->lock, lp->lock, 0);
+ lp->owner_pc = 0;
+ _raw_compare_and_swap(&lp->owner_cpu, lp->owner_cpu, 0);
}

/*
@@ -135,7 +149,6 @@ static inline int __raw_write_trylock(ra
return _raw_write_trylock_retry(rw);
}

-#define _raw_spin_relax(lock) cpu_relax()
#define _raw_read_relax(lock) cpu_relax()
#define _raw_write_relax(lock) cpu_relax()

diff -urpN linux-2.6/include/asm-s390/spinlock_types.h linux-2.6-patched/include/asm-s390/spinlock_types.h
--- linux-2.6/include/asm-s390/spinlock_types.h 2006-06-18 03:49:35.000000000 +0200
+++ linux-2.6-patched/include/asm-s390/spinlock_types.h 2006-09-19 12:59:36.000000000 +0200
@@ -6,16 +6,16 @@
#endif

typedef struct {
- volatile unsigned int lock;
+ volatile unsigned int owner_cpu;
+ volatile unsigned int owner_pc;
} __attribute__ ((aligned (4))) raw_spinlock_t;

#define __RAW_SPIN_LOCK_UNLOCKED { 0 }

typedef struct {
volatile unsigned int lock;
- volatile unsigned int owner_pc;
} raw_rwlock_t;

-#define __RAW_RW_LOCK_UNLOCKED { 0, 0 }
+#define __RAW_RW_LOCK_UNLOCKED { 0 }

#endif
-
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