[PATCH 1/5] s390/tick: Remove CIF_NOHZ_DELAY flag

[Mete Durlu <meted@linux.ibm.com>]

Remove obsolete tick delay heuristic [1]. The upcoming cpuidle driver
handles frequent sleep/wakeup cycles more effectively.

[1] https://lore.kernel.org/all/20090929122533.402715150@de.ibm.com/

Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Mete Durlu <meted@linux.ibm.com>
---
 arch/s390/include/asm/processor.h | 4 ----
 arch/s390/kernel/idle.c           | 1 -
 arch/s390/kernel/irq.c            | 4 ----
 arch/s390/kernel/smp.c            | 1 -
 4 files changed, 10 deletions(-)

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 78195ee5e99f..3666198cc364 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -14,12 +14,10 @@
 
 #include <linux/bits.h>
 
-#define CIF_NOHZ_DELAY		2	/* delay HZ disable for a tick */
 #define CIF_ENABLED_WAIT	5	/* in enabled wait state */
 #define CIF_MCCK_GUEST		6	/* machine check happening in guest */
 #define CIF_DEDICATED_CPU	7	/* this CPU is dedicated */
 
-#define _CIF_NOHZ_DELAY		BIT(CIF_NOHZ_DELAY)
 #define _CIF_ENABLED_WAIT	BIT(CIF_ENABLED_WAIT)
 #define _CIF_MCCK_GUEST		BIT(CIF_MCCK_GUEST)
 #define _CIF_DEDICATED_CPU	BIT(CIF_DEDICATED_CPU)
@@ -96,8 +94,6 @@ static __always_inline bool test_cpu_flag_of(int flag, int cpu)
 	return test_bit(flag, &per_cpu(pcpu_devices, cpu).flags);
 }
 
-#define arch_needs_cpu() test_cpu_flag(CIF_NOHZ_DELAY)
-
 static inline void get_cpu_id(struct cpuid *ptr)
 {
 	asm volatile("stidp %0" : "=Q" (*ptr));
diff --git a/arch/s390/kernel/idle.c b/arch/s390/kernel/idle.c
index 1f1b06b6b4ef..8c63f440da2e 100644
--- a/arch/s390/kernel/idle.c
+++ b/arch/s390/kernel/idle.c
@@ -42,7 +42,6 @@ void noinstr arch_cpu_idle(void)
 	/* Wait for external, I/O or machine check interrupt. */
 	psw_mask = PSW_KERNEL_BITS | PSW_MASK_WAIT |
 		   PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
-	clear_cpu_flag(CIF_NOHZ_DELAY);
 	set_cpu_flag(CIF_ENABLED_WAIT);
 	if (smp_cpu_mtid)
 		stcctm(MT_DIAG, smp_cpu_mtid, (u64 *)&idle->mt_cycles_enter);
diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
index d10a17e6531d..61d17954c34c 100644
--- a/arch/s390/kernel/irq.c
+++ b/arch/s390/kernel/irq.c
@@ -161,7 +161,6 @@ void noinstr do_io_irq(struct pt_regs *regs)
 	if (from_idle)
 		account_idle_time_irq();
 
-	set_cpu_flag(CIF_NOHZ_DELAY);
 	do {
 		regs->tpi_info = get_lowcore()->tpi_info;
 		if (get_lowcore()->tpi_info.adapter_IO)
@@ -358,9 +357,6 @@ static irqreturn_t do_ext_interrupt(int irq, void *dummy)
 	int index;
 
 	ext_code.int_code = regs->int_code;
-	if (ext_code.code != EXT_IRQ_CLK_COMP)
-		set_cpu_flag(CIF_NOHZ_DELAY);
-
 	index = ext_hash(ext_code.code);
 	rcu_read_lock();
 	hlist_for_each_entry_rcu(p, &ext_int_hash[index], entry) {
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 50bb499cf3e5..cd5ccbe3a18d 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -910,7 +910,6 @@ int __cpu_disable(void)
 	cregs[6].val  &= ~0xff000000UL;	/* disable all I/O interrupts */
 	cregs[14].val &= ~0x1f000000UL;	/* disable most machine checks */
 	__local_ctl_load(0, 15, cregs);
-	clear_cpu_flag(CIF_NOHZ_DELAY);
 	return 0;
 }
 
-- 
2.54.0