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>

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 */

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, SPINLOCK_LOCKVAL);
-
-	return _raw_compare_and_swap(&lp->lock, 0, new);
 }
 
 static inline int arch_spin_tryrelease_once(arch_spinlock_t *lp)
 {
-	unsigned int old = ~smp_processor_id();
+	return _raw_compare_and_swap(&lp->lock, SPINLOCK_LOCKVAL, 0);
-
-	return _raw_compare_and_swap(&lp->lock, old, 0);
 }
 
 static inline void arch_spin_lock(arch_spinlock_t *lp)

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;
 }

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);
 }
 
 /*

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);