s390/nohz: use a per-cpu flag for arch_needs_cpu

Move the nohz_delay bit from the s390_idle data structure to the
per-cpu flags. Clear the nohz delay flag in __cpu_disable and
remove the cpu hotplug notifier that used to do this.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Author: Martin Schwidefsky

arch/s390/include/asm/cputime.h

@@ -166,7 +166,6 @@ static inline clock_t cputime64_to_clock_t(cputime64_t cputime)
 }
 
 struct s390_idle_data {
-	int nohz_delay;
 	unsigned int sequence;
 	unsigned long long idle_count;
 	unsigned long long idle_time;
@@ -182,11 +181,4 @@ cputime64_t s390_get_idle_time(int cpu);
 
 #define arch_idle_time(cpu) s390_get_idle_time(cpu)
 
-static inline int s390_nohz_delay(int cpu)
-{
-	return __get_cpu_var(s390_idle).nohz_delay != 0;
-}
-
-#define arch_needs_cpu(cpu) s390_nohz_delay(cpu)
-
 #endif /* _S390_CPUTIME_H */

arch/s390/include/asm/processor.h

@@ -13,9 +13,11 @@
 
 #define CIF_MCCK_PENDING	0	/* machine check handling is pending */
 #define CIF_ASCE		1	/* user asce needs fixup / uaccess */
+#define CIF_NOHZ_DELAY		2	/* delay HZ disable for a tick */
 
 #define _CIF_MCCK_PENDING	(1<<CIF_MCCK_PENDING)
 #define _CIF_ASCE		(1<<CIF_ASCE)
+#define _CIF_NOHZ_DELAY		(1<<CIF_NOHZ_DELAY)
 
 
 #ifndef __ASSEMBLY__
@@ -43,6 +45,8 @@ static inline int test_cpu_flag(int flag)
 	return !!(S390_lowcore.cpu_flags & (1U << flag));
 }
 
+#define arch_needs_cpu() test_cpu_flag(CIF_NOHZ_DELAY)
+
 /*
  * Default implementation of macro that returns current
  * instruction pointer ("program counter").

arch/s390/kernel/irq.c

@@ -259,7 +259,7 @@ static irqreturn_t do_ext_interrupt(int irq, void *dummy)
 
 	ext_code = *(struct ext_code *) &regs->int_code;
 	if (ext_code.code != EXT_IRQ_CLK_COMP)
-		__get_cpu_var(s390_idle).nohz_delay = 1;
+		set_cpu_flag(CIF_NOHZ_DELAY);
 
 	index = ext_hash(ext_code.code);
 	rcu_read_lock();

arch/s390/kernel/smp.c

@@ -720,6 +720,7 @@ int __cpu_disable(void)
 	cregs[6]  &= ~0xff000000UL;	/* disable all I/O interrupts */
 	cregs[14] &= ~0x1f000000UL;	/* disable most machine checks */
 	__ctl_load(cregs, 0, 15);
+	clear_cpu_flag(CIF_NOHZ_DELAY);
 	return 0;
 }
 

arch/s390/kernel/vtime.c

@@ -163,7 +163,7 @@ void __kprobes vtime_stop_cpu(void)
 	/* Wait for external, I/O or machine check interrupt. */
 	psw_mask = PSW_KERNEL_BITS | PSW_MASK_WAIT | PSW_MASK_DAT |
 		PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
-	idle->nohz_delay = 0;
+	clear_cpu_flag(CIF_NOHZ_DELAY);
 
 	/* Call the assembler magic in entry.S */
 	psw_idle(idle, psw_mask);
@@ -378,25 +378,8 @@ void init_cpu_vtimer(void)
 	set_vtimer(VTIMER_MAX_SLICE);
 }
 
-static int s390_nohz_notify(struct notifier_block *self, unsigned long action,
-			    void *hcpu)
-{
-	struct s390_idle_data *idle;
-	long cpu = (long) hcpu;
-
-	idle = &per_cpu(s390_idle, cpu);
-	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_DYING:
-		idle->nohz_delay = 0;
-	default:
-		break;
-	}
-	return NOTIFY_OK;
-}
-
 void __init vtime_init(void)
 {
 	/* Enable cpu timer interrupts on the boot cpu. */
 	init_cpu_vtimer();
-	cpu_notifier(s390_nohz_notify, 0);
 }

drivers/s390/cio/airq.c

@@ -87,7 +87,7 @@ static irqreturn_t do_airq_interrupt(int irq, void *dummy)
 	struct airq_struct *airq;
 	struct hlist_head *head;
 
-	__this_cpu_write(s390_idle.nohz_delay, 1);
+	set_cpu_flag(CIF_NOHZ_DELAY);
 	tpi_info = (struct tpi_info *) &get_irq_regs()->int_code;
 	head = &airq_lists[tpi_info->isc];
 	rcu_read_lock();

drivers/s390/cio/cio.c

@@ -561,7 +561,7 @@ static irqreturn_t do_cio_interrupt(int irq, void *dummy)
 	struct subchannel *sch;
 	struct irb *irb;
 
-	__this_cpu_write(s390_idle.nohz_delay, 1);
+	set_cpu_flag(CIF_NOHZ_DELAY);
 	tpi_info = (struct tpi_info *) &get_irq_regs()->int_code;
 	irb = &__get_cpu_var(cio_irb);
 	sch = (struct subchannel *)(unsigned long) tpi_info->intparm;

include/linux/tick.h

@@ -108,7 +108,7 @@ extern struct tick_sched *tick_get_tick_sched(int cpu);
 extern void tick_irq_enter(void);
 extern int tick_oneshot_mode_active(void);
 #  ifndef arch_needs_cpu
-#   define arch_needs_cpu(cpu) (0)
+#   define arch_needs_cpu() (0)
 #  endif
 # else
 static inline void tick_clock_notify(void) { }

kernel/time/tick-sched.c

@@ -572,7 +572,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 	} while (read_seqretry(&jiffies_lock, seq));
 
 	if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
-	    arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
+	    arch_needs_cpu() || irq_work_needs_cpu()) {
 		next_jiffies = last_jiffies + 1;
 		delta_jiffies = 1;
 	} else {