[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, 27 insertions, 13 deletions

diff --git a/include/asm-s390/setup.h b/include/asm-s390/setup.h
index f1959732b6f..5d72eda8a11 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 5f00feaf1be..6b78af16999 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 f79a2216204..b7ac13f7aa3 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