[PATCH] 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@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 61 insertions, 23 deletions

diff --git a/arch/s390/kernel/head31.S b/arch/s390/kernel/head31.S
index 1fa9fa1ca74..1b952a3664e 100644
--- a/arch/s390/kernel/head31.S
+++ b/arch/s390/kernel/head31.S
@@ -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 --git a/arch/s390/kernel/head64.S b/arch/s390/kernel/head64.S
index 48998d50b00..b30e5897cdf 100644
--- a/arch/s390/kernel/head64.S
+++ b/arch/s390/kernel/head64.S
@@ -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 --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index b9b7958a226..8d76403fcf8 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -24,57 +24,76 @@ static int __init spin_retry_setup(char *str)
 }
 __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;