[PATCH] s390: cpu-idle notifier

This patch introduces a notifier chain for cpu idle.  There are two events
CPU_IDLE and CPU_NOT_IDLE that are called just before the cpu goes to sleep
and right after the cpu woke up again.  The notifier is used to simplify the
no-hz-timer-in-idle feature and the virtual cpu timers.  In addition the
virtual cpu timer functions have been moved to arch/s390/kernel/vtime.c, which
gives a nice separation between the timer functions related to real time and
the timer functions related to virtual cpu time.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/s390/kernel/Makefile

@@ -23,6 +23,8 @@ obj-$(CONFIG_BINFMT_ELF32)	+= binfmt_elf32.o
 obj-$(CONFIG_ARCH_S390_31)	+= entry.o reipl.o
 obj-$(CONFIG_ARCH_S390X)	+= entry64.o reipl64.o
 
+obj-$(CONFIG_VIRT_TIMER)	+= vtime.o
+
 #
 # This is just to get the dependencies...
 #

arch/s390/kernel/process.c

@@ -34,6 +34,8 @@
 #include <linux/delay.h>
 #include <linux/reboot.h>
 #include <linux/init.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -41,9 +43,7 @@
 #include <asm/io.h>
 #include <asm/processor.h>
 #include <asm/irq.h>
-#if defined(CONFIG_VIRT_TIMER) || defined (CONFIG_NO_IDLE_HZ)
 #include <asm/timer.h>
-#endif
 
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
 
@@ -68,13 +68,39 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
 }
 
 /*
- * The idle loop on a S390...
+ * Need to know about CPUs going idle?
  */
+static struct notifier_block *idle_chain;
+
+int register_idle_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_register(&idle_chain, nb);
+}
+EXPORT_SYMBOL(register_idle_notifier);
+
+int unregister_idle_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_unregister(&idle_chain, nb);
+}
+EXPORT_SYMBOL(unregister_idle_notifier);
+
+void do_monitor_call(struct pt_regs *regs, long interruption_code)
+{
+	/* disable monitor call class 0 */
+	__ctl_clear_bit(8, 15);
+
+	notifier_call_chain(&idle_chain, CPU_NOT_IDLE,
+			    (void *)(long) smp_processor_id());
+}
 
+/*
+ * The idle loop on a S390...
+ */
 void default_idle(void)
 {
 	psw_t wait_psw;
 	unsigned long reg;
+	int cpu, rc;
 
 	local_irq_disable();
         if (need_resched()) {
@@ -83,15 +109,18 @@ void default_idle(void)
                 return;
         }
 
-#if defined(CONFIG_VIRT_TIMER) || defined (CONFIG_NO_IDLE_HZ)
-	/*
-	 * hook to stop timers that should not tick while CPU is idle
-	 */
-	if (stop_timers()) {
+	/* CPU is going idle. */
+	cpu = smp_processor_id();
+	rc = notifier_call_chain(&idle_chain, CPU_IDLE, (void *)(long) cpu);
+	if (rc != NOTIFY_OK && rc != NOTIFY_DONE)
+		BUG();
+	if (rc != NOTIFY_OK) {
 		local_irq_enable();
 		return;
 	}
-#endif
+
+	/* enable monitor call class 0 */
+	__ctl_set_bit(8, 15);
 
 	/* 
 	 * Wait for external, I/O or machine check interrupt and

arch/s390/kernel/s390_ksyms.c

@@ -19,9 +19,6 @@
 #ifdef CONFIG_IP_MULTICAST
 #include <net/arp.h>
 #endif
-#ifdef CONFIG_VIRT_TIMER
-#include <asm/timer.h>
-#endif
 
 /*
  * memory management

arch/s390/kernel/smp.c

@@ -509,6 +509,7 @@ void __init smp_check_cpus(unsigned int max_cpus)
  *      Activate a secondary processor.
  */
 extern void init_cpu_timer(void);
+extern void init_cpu_vtimer(void);
 extern int pfault_init(void);
 extern int pfault_token(void);
 
@@ -518,6 +519,9 @@ int __devinit start_secondary(void *cpuvoid)
         cpu_init();
         /* init per CPU timer */
         init_cpu_timer();
+#ifdef CONFIG_VIRT_TIMER
+        init_cpu_vtimer();
+#endif
 #ifdef CONFIG_PFAULT
 	/* Enable pfault pseudo page faults on this cpu. */
 	pfault_init();

arch/s390/kernel/traps.c

@@ -64,9 +64,7 @@ extern void pfault_fini(void);
 extern void pfault_interrupt(struct pt_regs *regs, __u16 error_code);
 static ext_int_info_t ext_int_pfault;
 #endif
-#if defined(CONFIG_NO_IDLE_HZ) || defined(CONFIG_VIRT_TIMER)
 extern pgm_check_handler_t do_monitor_call;
-#endif
 
 #define stack_pointer ({ void **sp; asm("la %0,0(15)" : "=&d" (sp)); sp; })
 
@@ -620,9 +618,8 @@ void __init trap_init(void)
 #endif /* CONFIG_ARCH_S390X */
         pgm_check_table[0x15] = &operand_exception;
         pgm_check_table[0x1C] = &privileged_op;
-#if defined(CONFIG_VIRT_TIMER) || defined(CONFIG_NO_IDLE_HZ)
 	pgm_check_table[0x40] = &do_monitor_call;
-#endif
+
 	if (MACHINE_IS_VM) {
 		/*
 		 * First try to get pfault pseudo page faults going.

include/asm-s390/processor.h

@@ -319,6 +319,16 @@ static inline void disabled_wait(unsigned long code)
 #endif /* __s390x__ */
 }
 
+/*
+ * CPU idle notifier chain.
+ */
+#define CPU_IDLE	0
+#define CPU_NOT_IDLE	1
+
+struct notifier_block;
+int register_idle_notifier(struct notifier_block *nb);
+int unregister_idle_notifier(struct notifier_block *nb);
+
 #endif
 
 #endif                                 /* __ASM_S390_PROCESSOR_H           */