[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>

6 files changed, 88 insertions, 36 deletions

diff --git a/arch/s390/kernel/head31.S b/arch/s390/kernel/head31.S
index 1fa9fa1ca740..1b952a3664e2 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 48998d50b00a..b30e5897cdf7 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 b9b7958a226a..8d76403fcf89 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;
 
diff --git a/include/asm-s390/setup.h b/include/asm-s390/setup.h
index f1959732b6fd..5d72eda8a11b 100644
--- a/include/asm-s390/setup.h
+++ b/include/asm-s390/setup.h
@@ -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 --git a/include/asm-s390/spinlock.h b/include/asm-s390/spinlock.h
index 5f00feaf1be6..6b78af16999b 100644
--- a/include/asm-s390/spinlock.h
+++ b/include/asm-s390/spinlock.h
@@ -13,6 +13,8 @@
 
 #if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ > 2)
 
+#include <linux/smp.h>
+
 static inline int
 _raw_compare_and_swap(volatile unsigned int *lock,
                       unsigned int old, unsigned int new)
@@ -50,34 +52,46 @@ _raw_compare_and_swap(volatile unsigned int *lock,
  * (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);
-
-        if (unlikely(_raw_compare_and_swap(&lp->lock, 0, pc) != 0))
-                _raw_spin_lock_wait(lp, pc);
+        int old;
+
+        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);
 }
                 
 /*
@@ -154,7 +168,6 @@ static inline int __raw_write_trylock(raw_rwlock_t *rw)
         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 --git a/include/asm-s390/spinlock_types.h b/include/asm-s390/spinlock_types.h
index f79a2216204f..b7ac13f7aa37 100644
--- a/include/asm-s390/spinlock_types.h
+++ b/include/asm-s390/spinlock_types.h
@@ -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