s390/spinlock: optimize spinlock code sequence

Use lowcore constant to improve the code generated for spinlocks.

[ Martin Schwidefsky: patch breakdown and code beautification ]

Signed-off-by: Philipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

5 files changed, 21 insertions, 10 deletions

diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index bbf8141408cd..3b476eb92f20 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -139,7 +139,7 @@ struct _lowcore {
         __u32   percpu_offset;                  /* 0x02f0 */
         __u32   machine_flags;                  /* 0x02f4 */
         __u32   ftrace_func;                    /* 0x02f8 */
-        __u8    pad_0x02fc[0x0300-0x02fc];      /* 0x02fc */
+        __u32   spinlock_lockval;               /* 0x02fc */
 
         /* Interrupt response block */
         __u8    irb[64];                        /* 0x0300 */
@@ -285,7 +285,8 @@ struct _lowcore {
         __u64   machine_flags;                  /* 0x0388 */
         __u64   ftrace_func;                    /* 0x0390 */
         __u64   gmap;                           /* 0x0398 */
-        __u8    pad_0x03a0[0x0400-0x03a0];      /* 0x03a0 */
+        __u32   spinlock_lockval;               /* 0x03a0 */
+        __u8    pad_0x03a0[0x0400-0x03a4];      /* 0x03a4 */
 
         /* Interrupt response block. */
         __u8    irb[64];                        /* 0x0400 */
diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index b60212a02d08..5a0b2882ad48 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -11,6 +11,8 @@
 
 #include <linux/smp.h>
 
+#define SPINLOCK_LOCKVAL (S390_lowcore.spinlock_lockval)
+
 extern int spin_retry;
 
 static inline int
@@ -40,6 +42,11 @@ int arch_spin_trylock_retry(arch_spinlock_t *);
 void arch_spin_relax(arch_spinlock_t *);
 void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);
 
+static inline u32 arch_spin_lockval(int cpu)
+{
+        return ~cpu;
+}
+
 static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
 {
         return lock.lock == 0;
@@ -52,16 +59,12 @@ static inline int arch_spin_is_locked(arch_spinlock_t *lp)
 
 static inline int arch_spin_trylock_once(arch_spinlock_t *lp)
 {
-        unsigned int new = ~smp_processor_id();
-
-        return _raw_compare_and_swap(&lp->lock, 0, new);
+        return _raw_compare_and_swap(&lp->lock, 0, SPINLOCK_LOCKVAL);
 }
 
 static inline int arch_spin_tryrelease_once(arch_spinlock_t *lp)
 {
-        unsigned int old = ~smp_processor_id();
-
-        return _raw_compare_and_swap(&lp->lock, old, 0);
+        return _raw_compare_and_swap(&lp->lock, SPINLOCK_LOCKVAL, 0);
 }
 
 static inline void arch_spin_lock(arch_spinlock_t *lp)
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 1f5536c2fd02..7c5b05fa2194 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -373,6 +373,10 @@ static void __init setup_lowcore(void)
         mem_assign_absolute(S390_lowcore.restart_source, lc->restart_source);
         mem_assign_absolute(S390_lowcore.restart_psw, lc->restart_psw);
 
+#ifdef CONFIG_SMP
+        lc->spinlock_lockval = arch_spin_lockval(0);
+#endif
+
         set_prefix((u32)(unsigned long) lc);
         lowcore_ptr[0] = lc;
 }
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 86e65ec3422b..1f0b474041c4 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -170,6 +170,7 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
         lc->panic_stack = pcpu->panic_stack + PAGE_SIZE
                 - STACK_FRAME_OVERHEAD - sizeof(struct pt_regs);
         lc->cpu_nr = cpu;
+        lc->spinlock_lockval = arch_spin_lockval(cpu);
 #ifndef CONFIG_64BIT
         if (MACHINE_HAS_IEEE) {
                 lc->extended_save_area_addr = get_zeroed_page(GFP_KERNEL);
@@ -226,6 +227,7 @@ static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
         cpumask_set_cpu(cpu, mm_cpumask(&init_mm));
         atomic_inc(&init_mm.context.attach_count);
         lc->cpu_nr = cpu;
+        lc->spinlock_lockval = arch_spin_lockval(cpu);
         lc->percpu_offset = __per_cpu_offset[cpu];
         lc->kernel_asce = S390_lowcore.kernel_asce;
         lc->machine_flags = S390_lowcore.machine_flags;
@@ -809,6 +811,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
 void __init smp_setup_processor_id(void)
 {
         S390_lowcore.cpu_nr = 0;
+        S390_lowcore.spinlock_lockval = arch_spin_lockval(0);
 }
 
 /*
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 4a3b33b2dbb9..3ca9de4d9cb9 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -27,7 +27,7 @@ __setup("spin_retry=", spin_retry_setup);
 void arch_spin_lock_wait(arch_spinlock_t *lp)
 {
         int count = spin_retry;
-        unsigned int cpu = ~smp_processor_id();
+        unsigned int cpu = SPINLOCK_LOCKVAL;
         unsigned int owner;
 
         while (1) {
@@ -54,7 +54,7 @@ EXPORT_SYMBOL(arch_spin_lock_wait);
 void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
 {
         int count = spin_retry;
-        unsigned int cpu = ~smp_processor_id();
+        unsigned int cpu = SPINLOCK_LOCKVAL;
         unsigned int owner;
 
         local_irq_restore(flags);