improve SMP reschedule and idle routines

Index: linux-2.6/kernel/sched.c
===================================================================
@@ -845,21 +845,28 @@ static void deactivate_task(struct task_
 #ifdef CONFIG_SMP
 static void resched_task(task_t *p)
 {
-	int need_resched, nrpolling;
+	int cpu;
 
 	assert_spin_locked(&task_rq(p)->lock);
 
-	/* minimise the chance of sending an interrupt to poll_idle() */
-	nrpolling = test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
-	need_resched = test_and_set_tsk_thread_flag(p,TIF_NEED_RESCHED);
-	nrpolling |= test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
+	if (unlikely(test_tsk_thread_flag(p, TIF_NEED_RESCHED)))
+		return;
+	
+	set_tsk_thread_flag(p, TIF_NEED_RESCHED);
 
-	if (!need_resched && !nrpolling && (task_cpu(p) != smp_processor_id()))
-		smp_send_reschedule(task_cpu(p));
+	cpu = task_cpu(p);
+	if (cpu == smp_processor_id())
+		return;
+
+	/* NEED_RESCHED must be visible before we test POLLING_NRFLAG */
+	smp_mb();
+	if (!test_tsk_thread_flag(p, TIF_POLLING_NRFLAG))
+		smp_send_reschedule(cpu);
 }
 #else
 static inline void resched_task(task_t *p)
 {
+	assert_spin_locked(&task_rq(p)->lock);
 	set_tsk_need_resched(p);
 }
 #endif

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Index: linux-2.6/init/main.c
===================================================================
@@ -382,7 +382,7 @@ static void noinline rest_init(void)
 	kernel_thread(init, NULL, CLONE_FS | CLONE_SIGHAND);
 	numa_default_policy();
 	unlock_kernel();
-	preempt_enable_no_resched();
+	/* Don't re-enable preemption */
 	cpu_idle();
 } 
 

Index: linux-2.6/arch/i386/kernel/apm.c
===================================================================
@@ -767,8 +767,20 @@ static int set_system_power_state(u_shor
 static int apm_do_idle(void)
 {
 	u32	eax;
+	u8	ret;
+	int	idled = 0;
 
-	if (apm_bios_call_simple(APM_FUNC_IDLE, 0, 0, &eax)) {
+	clear_thread_flag(TIF_POLLING_NRFLAG);
+	smp_mb__after_clear_bit();
+	if (!need_resched()) {
+		idled = 1;
+		ret = apm_bios_call_simple(APM_FUNC_IDLE, 0, 0, &eax);
+	}
+	set_thread_flag(TIF_POLLING_NRFLAG);
+	if (!idled)
+		return 0;
+
+	if (ret) {
 		static unsigned long t;
 
 		/* This always fails on some SMP boards running UP kernels.

Index: linux-2.6/drivers/acpi/processor_idle.c
===================================================================
@@ -164,6 +164,14 @@ acpi_processor_power_activate (
 	return;
 }
 
+static void acpi_safe_halt (void)
+{
+	clear_thread_flag(TIF_POLLING_NRFLAG);
+	smp_mb__after_clear_bit();
+	while (!need_resched())
+		safe_halt();
+	set_thread_flag(TIF_POLLING_NRFLAG);
+}
 
 static atomic_t 	c3_cpu_count;
 

@@ -176,7 +184,7 @@ static void acpi_processor_idle (void)
 	int			sleep_ticks = 0;
 	u32			t1, t2 = 0;
 
-	pr = processors[_smp_processor_id()];
+	pr = processors[smp_processor_id()];
 	if (!pr)
 		return;
 

@@ -196,8 +204,13 @@ static void acpi_processor_idle (void)
 	}
 
 	cx = pr->power.state;
-	if (!cx)
-		goto easy_out;
+	if (!cx) {
+		if (pm_idle_save)
+			pm_idle_save();
+		else
+			acpi_safe_halt();
+		return;
+	}
 
 	/*
 	 * Check BM Activity

@@ -277,7 +290,8 @@ static void acpi_processor_idle (void)
 		if (pm_idle_save)
 			pm_idle_save();
 		else
-			safe_halt();
+			acpi_safe_halt();
+
 		/*
                  * TBD: Can't get time duration while in C1, as resumes
 		 *      go to an ISR rather than here.  Need to instrument

@@ -407,16 +421,6 @@ end:
 	 */
 	if (next_state != pr->power.state)
 		acpi_processor_power_activate(pr, next_state);
-
-	return;
-
- easy_out:
-	/* do C1 instead of busy loop */
-	if (pm_idle_save)
-		pm_idle_save();
-	else
-		safe_halt();
-	return;
 }
 
 

Index: linux-2.6/arch/i386/kernel/smpboot.c
===================================================================
@@ -477,6 +477,8 @@ set_cpu_sibling_map(int cpu)
  */
 static void __devinit start_secondary(void *unused)
 {
+	preempt_disable();
+
 	/*
 	 * Dont put anything before smp_callin(), SMP
 	 * booting is too fragile that we want to limit the

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272 lines not on this page · raw message

Index: linux-2.6/arch/ia64/kernel/process.c
===================================================================
@@ -195,11 +195,16 @@ update_pal_halt_status(int status)
 void
 default_idle (void)
 {
-	while (!need_resched())
-		if (can_do_pal_halt)
+	if (can_do_pal_halt) {
+		clear_thread_flag(TIF_POLLING_NRFLAG);
+		smp_mb__after_clear_bit();
+		while (!need_resched())
 			safe_halt();
-		else
+		set_thread_flag(TIF_POLLING_NRFLAG);
+	} else {
+		while (!need_resched())
 			cpu_relax();
+	}
 }
 
 #ifdef CONFIG_HOTPLUG_CPU

@@ -261,18 +266,17 @@ void __attribute__((noreturn))
 cpu_idle (void)
 {
 	void (*mark_idle)(int) = ia64_mark_idle;
-
-	set_tsk_need_resched(current);
+  	int cpu = smp_processor_id();
+	set_need_resched();
+	set_thread_flag(TIF_POLLING_NRFLAG);
 
 	/* endless idle loop with no priority at all */
 	while (1) {
+		if (!need_resched()) {
+			void (*idle)(void);
 #ifdef CONFIG_SMP
-		if (!need_resched())
 			min_xtp();
 #endif
-		while (!need_resched()) {
-			void (*idle)(void);
-
 			if (__get_cpu_var(cpu_idle_state))
 				__get_cpu_var(cpu_idle_state) = 0;
 

@@ -284,17 +288,17 @@ cpu_idle (void)
 			if (!idle)
 				idle = default_idle;
 			(*idle)();
-		}
-
-		if (mark_idle)
-			(*mark_idle)(0);
-
+			if (mark_idle)
+				(*mark_idle)(0);
 #ifdef CONFIG_SMP
-		normal_xtp();
+			normal_xtp();
 #endif
+		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
-		if (cpu_is_offline(smp_processor_id()))
+		if (cpu_is_offline(cpu))
 			play_dead();
 	}
 }

Index: linux-2.6/arch/ia64/kernel/smpboot.c
===================================================================
@@ -393,6 +393,8 @@ smp_callin (void)
 int __devinit
 start_secondary (void *unused)
 {
+	preempt_disable();
+
 	/* Early console may use I/O ports */
 	ia64_set_kr(IA64_KR_IO_BASE, __pa(ia64_iobase));
 	Dprintk("start_secondary: starting CPU 0x%x\n", hard_smp_processor_id());

Index: linux-2.6/arch/ppc64/kernel/smp.c
===================================================================
@@ -561,7 +561,10 @@ int __devinit __cpu_up(unsigned int cpu)
 /* Activate a secondary processor. */
 int __devinit start_secondary(void *unused)
 {
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
+	
+	preempt_disable();
+	cpu = smp_processor_id();
 
 	atomic_inc(&init_mm.mm_count);
 	current->active_mm = &init_mm;

Index: linux-2.6/arch/sparc64/kernel/smp.c
===================================================================
@@ -144,6 +144,9 @@ void __init smp_callin(void)
 		membar("#LoadLoad");
 
 	cpu_set(cpuid, cpu_online_map);
+
+	/* idle thread is expected to have preempt disabled */
+	preempt_disable();
 }
 
 void cpu_panic(void)

@@ -1167,20 +1170,9 @@ void __init smp_cpus_done(unsigned int m
 	       (bogosum/(5000/HZ))%100);
 }
 
-/* This needn't do anything as we do not sleep the cpu
- * inside of the idler task, so an interrupt is not needed
- * to get a clean fast response.
- *
- * XXX Reverify this assumption... -DaveM
- *
- * Addendum: We do want it to do something for the signal
- *           delivery case, we detect that by just seeing
- *           if we are trying to send this to an idler or not.
- */
 void smp_send_reschedule(int cpu)
 {
-	if (cpu_data(cpu).idle_volume == 0)
-		smp_receive_signal(cpu);
+	smp_receive_signal(cpu);
 }
 
 /* This is a nop because we capture all other cpus

Index: linux-2.6/arch/sparc64/kernel/process.c
===================================================================
@@ -74,7 +74,9 @@ void cpu_idle(void)
 		while (!need_resched())
 			barrier();
 
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
 	}
 }

@@ -83,21 +85,31 @@ void cpu_idle(void)
 
 /*
  * the idle loop on a UltraMultiPenguin...
+ * 
+ * TIF_POLLING_NRFLAG is set because we do not sleep the cpu
+ * inside of the idler task, so an interrupt is not needed
+ * to get a clean fast response.
+ *
+ * XXX Reverify this assumption... -DaveM
+ *
+ * Addendum: We do want it to do something for the signal
+ *           delivery case, we detect that by just seeing
+ *           if we are trying to send this to an idler or not.
  */
-#define idle_me_harder()	(cpu_data(smp_processor_id()).idle_volume += 1)
-#define unidle_me()		(cpu_data(smp_processor_id()).idle_volume = 0)
 void cpu_idle(void)
 {
+	cpuinfo_sparc *cpuinfo = &local_cpu_data();
 	set_thread_flag(TIF_POLLING_NRFLAG);
+
 	while(1) {
 		if (need_resched()) {
-			unidle_me();
-			clear_thread_flag(TIF_POLLING_NRFLAG);
+			cpuinfo->idle_volume = 0;
+			preempt_enable_no_resched();
 			schedule();
-			set_thread_flag(TIF_POLLING_NRFLAG);
+			preempt_disable();
 			check_pgt_cache();
 		}
-		idle_me_harder();
+		cpuinfo->idle_volume++;
 
 		/* The store ordering is so that IRQ handlers on
 		 * other cpus see our increasing idleness for the buddy

Index: linux-2.6/arch/alpha/kernel/process.c
===================================================================
@@ -43,22 +43,21 @@
 #include "proto.h"
 #include "pci_impl.h"
 
-void default_idle(void)
-{
-	barrier();
-}
-
 void
 cpu_idle(void)
 {
+	set_need_resched();
+	set_thread_flag(TIF_POLLING_NRFLAG);
+	
 	while (1) {
-		void (*idle)(void) = default_idle;
 		/* FIXME -- EV6 and LCA45 know how to power down
 		   the CPU.  */
 
 		while (!need_resched())
-			idle();
+			cpu_relax();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/alpha/kernel/smp.c
===================================================================
@@ -128,7 +128,11 @@ wait_boot_cpu_to_stop(int cpuid)
 void __init
 smp_callin(void)
 {
-	int cpuid = hard_smp_processor_id();
+	int cpuid;
+	
+	preempt_disable();
+
+	cpuid = hard_smp_processor_id();
 
 	if (cpu_test_and_set(cpuid, cpu_online_map)) {
 		printk("??, cpu 0x%x already present??\n", cpuid);

Index: linux-2.6/arch/s390/kernel/smp.c
===================================================================
@@ -528,6 +528,8 @@ extern void pfault_fini(void);
 
 int __devinit start_secondary(void *cpuvoid)
 {
+	preempt_disable();
+
         /* Setup the cpu */
         cpu_init();
         /* init per CPU timer */

Index: linux-2.6/arch/sparc/kernel/process.c
===================================================================
@@ -72,6 +72,13 @@ struct thread_info *current_set[NR_CPUS]
  */
 void default_idle(void)
 {
+	if (pm_idle) {
+		while (!need_resched())
+			(*pm_idle)();
+	} else {
+		while (!need_resched())
+			cpu_relax();
+	}
 }
 
 #ifndef CONFIG_SMP

@@ -83,6 +90,8 @@ void default_idle(void)
  */
 void cpu_idle(void)
 {
+	set_need_resched();
+
 	/* endless idle loop with no priority at all */
 	for (;;) {
 		if (ARCH_SUN4C_SUN4) {

@@ -92,12 +101,11 @@ void cpu_idle(void)
 			static unsigned long fps;
 			unsigned long now;
 			unsigned long faults;
-			unsigned long flags;
 
 			extern unsigned long sun4c_kernel_faults;
 			extern void sun4c_grow_kernel_ring(void);
 
-			local_irq_save(flags);
+			local_irq_disable();
 			now = jiffies;
 			count -= (now - last_jiffies);
 			last_jiffies = now;

@@ -113,14 +121,14 @@ void cpu_idle(void)
 					sun4c_grow_kernel_ring();
 				}
 			}
-			local_irq_restore(flags);
+			local_irq_enable();
 		}
 
-		while((!need_resched()) && pm_idle) {
-			(*pm_idle)();
-		}
+		default_idle();
 
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
 	}
 }

@@ -130,13 +138,19 @@ void cpu_idle(void)
 /* This is being executed in task 0 'user space'. */
 void cpu_idle(void)
 {
+	
+        set_need_resched();
+        set_thread_flag(TIF_POLLING_NRFLAG);
+			
 	/* endless idle loop with no priority at all */
 	while(1) {
-		if(need_resched()) {
-			schedule();
-			check_pgt_cache();
-		}
-		barrier(); /* or else gcc optimizes... */
+		while (!need_resched())
+			cpu_relax();
+
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+		check_pgt_cache();
 	}
 }
 

Index: linux-2.6/arch/ppc/kernel/idle.c
===================================================================
@@ -50,8 +50,6 @@ void default_idle(void)
 		}
 #endif
 	}
-	if (need_resched())
-		schedule();
 }
 
 /*

@@ -59,11 +57,20 @@ void default_idle(void)
  */
 void cpu_idle(void)
 {
-	for (;;)
-		if (ppc_md.idle != NULL)
-			ppc_md.idle();
-		else
-			default_idle();
+	set_need_resched();
+
+	for (;;) {
+		while (need_resched()) {
+			if (ppc_md.idle != NULL)
+				ppc_md.idle();
+			else
+				default_idle();
+		}
+
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 #if defined(CONFIG_SYSCTL) && defined(CONFIG_6xx)

Index: linux-2.6/arch/m32r/kernel/process.c
===================================================================
@@ -94,6 +94,8 @@ static void poll_idle (void)
  */
 void cpu_idle (void)
 {
+	set_need_resched();
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched()) {

@@ -104,7 +106,9 @@ void cpu_idle (void)
 
 			idle();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/frv/kernel/process.c
===================================================================
@@ -77,16 +77,21 @@ void (*idle)(void) = core_sleep_idle;
  */
 void cpu_idle(void)
 {
+	int cpu = smp_processor_id();
+	set_need_resched();
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched()) {
-			irq_stat[smp_processor_id()].idle_timestamp = jiffies;
+			irq_stat[cpu].idle_timestamp = jiffies;
 
 			if (!frv_dma_inprogress && idle)
 				idle();
 		}
-
+		
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/cris/kernel/process.c
===================================================================
@@ -191,6 +191,8 @@ extern void default_idle(void);
  */
 void cpu_idle (void)
 {
+	set_need_resched();
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched()) {

@@ -201,7 +203,9 @@ void cpu_idle (void)
 
 			idle();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 
 }

Index: linux-2.6/arch/mips/kernel/smp.c
===================================================================
@@ -83,7 +83,11 @@ extern ATTRIB_NORET void cpu_idle(void);
  */
 asmlinkage void start_secondary(void)
 {
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
+
+	preempt_disable();
+	
+	cpu = smp_processor_id();
 
 	cpu_probe();
 	cpu_report();

Index: linux-2.6/arch/parisc/kernel/process.c
===================================================================
@@ -88,11 +88,16 @@ void default_idle(void)
  */
 void cpu_idle(void)
 {
+	set_need_resched();
+	set_thread_flag(TIF_POLLING_NRFLAG);
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched())
 			barrier();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
 	}
 }

Index: linux-2.6/arch/ppc/kernel/smp.c
===================================================================
@@ -326,6 +326,8 @@ int __devinit start_secondary(void *unus
 {
 	int cpu;
 
+	preempt_disable();
+
 	atomic_inc(&init_mm.mm_count);
 	current->active_mm = &init_mm;
 

Index: linux-2.6/arch/sh/kernel/process.c
===================================================================
@@ -51,28 +51,26 @@ void enable_hlt(void)
 
 EXPORT_SYMBOL(enable_hlt);
 
-void default_idle(void)
+void cpu_idle(void)
 {
+	set_need_resched();
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		if (hlt_counter) {
-			while (1)
-				if (need_resched())
-					break;
+			while (!need_resched())
+				cpu_relax();
 		} else {
 			while (!need_resched())
 				cpu_sleep();
 		}
 
+		preempt_disable_no_resched();
 		schedule();
+		preempt_enable();
 	}
 }
 
-void cpu_idle(void)
-{
-	default_idle();
-}
-
 void machine_restart(char * __unused)
 {
 	/* SR.BL=1 and invoke address error to let CPU reset (manual reset) */

Index: linux-2.6/arch/m68k/kernel/process.c
===================================================================
@@ -98,11 +98,15 @@ void (*idle)(void) = default_idle;
  */
 void cpu_idle(void)
 {
+	set_need_resched();
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched())
 			idle();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/mips/kernel/process.c
===================================================================
@@ -53,12 +53,16 @@ void default_idle (void)
  */
 ATTRIB_NORET void cpu_idle(void)
 {
+	set_need_resched();
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched())
 			if (cpu_wait)
 				(*cpu_wait)();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable()
 	}
 }
 

Index: linux-2.6/arch/m68knommu/kernel/process.c
===================================================================
@@ -45,11 +45,8 @@ asmlinkage void ret_from_fork(void);
  */
 void default_idle(void)
 {
-	while(1) {
-		if (need_resched())
-			__asm__("stop #0x2000" : : : "cc");
-		schedule();
-	}
+	while (!need_resched())
+		__asm__("stop #0x2000" : : : "cc");
 }
 
 void (*idle)(void) = default_idle;

@@ -62,8 +59,15 @@ void (*idle)(void) = default_idle;
  */
 void cpu_idle(void)
 {
+	set_need_resched();
+
 	/* endless idle loop with no priority at all */
-	idle();
+	while (1) {
+		idle();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 void machine_restart(char * __unused)

Index: linux-2.6/arch/sh/kernel/smp.c
===================================================================
@@ -109,7 +109,11 @@ int __cpu_up(unsigned int cpu)
 
 int start_secondary(void *unused)
 {
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
+	
+	preempt_disable();
+	
+	cpu = smp_processor_id();
 
 	atomic_inc(&init_mm.mm_count);
 	current->active_mm = &init_mm;

Index: linux-2.6/arch/parisc/kernel/smp.c
===================================================================
@@ -462,6 +462,8 @@ void __init smp_callin(void)
 	void *istack;
 #endif
 
+	preempt_disable();
+
 	smp_cpu_init(slave_id);
 
 #if 0	/* NOT WORKING YET - see entry.S */

Index: linux-2.6/arch/m32r/kernel/smpboot.c
===================================================================
@@ -424,6 +424,7 @@ void __init smp_cpus_done(unsigned int m
  *==========================================================================*/
 int __init start_secondary(void *unused)
 {
+	preempt_disable();
 	cpu_init();
 	smp_callin();
 	while (!cpu_isset(smp_processor_id(), smp_commenced_mask))

Index: linux-2.6/arch/s390/kernel/process.c
===================================================================
@@ -101,11 +101,6 @@ void default_idle(void)
 	int cpu, rc;
 
 	local_irq_disable();
-        if (need_resched()) {
-		local_irq_enable();
-                schedule();
-                return;
-        }
 
 	/* CPU is going idle. */
 	cpu = smp_processor_id();

@@ -121,7 +116,7 @@ void default_idle(void)
 	__ctl_set_bit(8, 15);
 
 #ifdef CONFIG_HOTPLUG_CPU
-	if (cpu_is_offline(smp_processor_id()))
+	if (cpu_is_offline(cpu))
 		cpu_die();
 #endif
 

@@ -161,8 +156,15 @@ void default_idle(void)
 
 void cpu_idle(void)
 {
-	for (;;)
-		default_idle();
+	set_need_resched();
+
+	for (;;) {
+		while (!need_resched())
+			default_idle();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 void show_regs(struct pt_regs *regs)

Index: linux-2.6/arch/sh64/kernel/process.c
===================================================================
@@ -307,23 +307,21 @@ __setup("hlt", hlt_setup);
 
 static inline void hlt(void)
 {
-	if (hlt_counter)
-		return;
-
 	__asm__ __volatile__ ("sleep" : : : "memory");
 }
 
 /*
  * The idle loop on a uniprocessor SH..
  */
-void default_idle(void)
+void cpu_idle(void)
 {
+	set_need_resched();
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		if (hlt_counter) {
-			while (1)
-				if (need_resched())
-					break;
+			while (!need_resched())
+				cpu_relax();
 		} else {
 			local_irq_disable();
 			while (!need_resched()) {

@@ -334,13 +332,11 @@ void default_idle(void)
 			}
 			local_irq_enable();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
-}
 
-void cpu_idle(void)
-{
-	default_idle();
 }
 
 void machine_restart(char * __unused)

Index: linux-2.6/arch/arm26/kernel/process.c
===================================================================
@@ -73,16 +73,16 @@ __setup("hlt", hlt_setup);
  */
 void cpu_idle(void)
 {
+	set_need_resched();
+
 	/* endless idle loop with no priority at all */
-	preempt_disable();
 	while (1) {
-		while (!need_resched()) {
-			local_irq_disable();
-			if (!need_resched() && !hlt_counter)
-				local_irq_enable();
-		}
+		while (!need_resched())
+			cpu_relax();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
 	}
-	schedule();
 }
 
 static char reboot_mode = 'h';

Index: linux-2.6/arch/arm/kernel/process.c
===================================================================
@@ -84,10 +84,14 @@ EXPORT_SYMBOL(pm_power_off);
  */
 void default_idle(void)
 {
-	local_irq_disable();
-	if (!need_resched() && !hlt_counter)
-		arch_idle();
-	local_irq_enable();
+	if (hlt_counter)
+		cpu_relax()
+	else {
+		local_irq_disable();
+		if (!need_resched())
+			arch_idle();
+		local_irq_enable();
+	}
 }
 
 /*

@@ -97,6 +101,7 @@ void default_idle(void)
  */
 void cpu_idle(void)
 {
+	set_need_resched();
 	local_fiq_enable();
 
 	/* endless idle loop with no priority at all */

@@ -104,13 +109,13 @@ void cpu_idle(void)
 		void (*idle)(void) = pm_idle;
 		if (!idle)
 			idle = default_idle;
-		preempt_disable();
 		leds_event(led_idle_start);
 		while (!need_resched())
 			idle();
 		leds_event(led_idle_end);
-		preempt_enable();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/h8300/kernel/process.c
===================================================================
@@ -53,22 +53,17 @@ asmlinkage void ret_from_fork(void);
 #if !defined(CONFIG_H8300H_SIM) && !defined(CONFIG_H8S_SIM)
 void default_idle(void)
 {
-	while(1) {
-		if (need_resched()) {
-			local_irq_enable();
-			__asm__("sleep");
-			local_irq_disable();
-		}
-		schedule();
+	local_irq_disable();
+	if (need_resched()) {
+		local_irq_enable();
+		/* XXX: race here! What if need_resched() gets set now? */
+		__asm__("sleep");
 	}
 }
 #else
 void default_idle(void)
 {
-	while(1) {
-		if (need_resched())
-			schedule();
-	}
+	cpu_relax();
 }
 #endif
 void (*idle)(void) = default_idle;

@@ -81,7 +76,14 @@ void (*idle)(void) = default_idle;
  */
 void cpu_idle(void)
 {
-	idle();
+	set_need_resched();
+	while (1) {
+		while (!need_resched())
+			idle();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 void machine_restart(char * __unused)

Index: linux-2.6/arch/xtensa/kernel/process.c
===================================================================
@@ -91,13 +91,15 @@ coprocessor_info_t coprocessor_info[] = 
 void cpu_idle(void)
 {
   	local_irq_enable();
+	set_need_resched();
 
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched())
 			platform_idle();
-		preempt_enable();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/v850/kernel/process.c
===================================================================
@@ -36,11 +36,8 @@ extern void ret_from_fork (void);
 /* The idle loop.  */
 void default_idle (void)
 {
-	while (1) {
-		while (! need_resched ())
-			asm ("halt; nop; nop; nop; nop; nop" ::: "cc");
-		schedule ();
-	}
+	while (! need_resched ())
+		asm ("halt; nop; nop; nop; nop; nop" ::: "cc");
 }
 
 void (*idle)(void) = default_idle;

@@ -53,8 +50,17 @@ void (*idle)(void) = default_idle;
  */
 void cpu_idle (void)
 {
+	set_need_resched();
+	
 	/* endless idle loop with no priority at all */
-	(*idle) ();
+	while (1) {
+		while (!need_resched())
+			(*idle) ();
+
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 /*

@@ -4163,6 +4163,14 @@ void show_state(void)
 	read_unlock(&tasklist_lock);
 }
 
+/**
+ * init_idle - set up an idle thread for a given CPU
+ * @idle: task in question
+ * @cpu: cpu the idle task belongs to
+ *
+ * NOTE: this function does not set the idle thread's NEED_RESCHED
+ * flag, to make booting more robust.
+ */
 void __devinit init_idle(task_t *idle, int cpu)
 {
 	runqueue_t *rq = cpu_rq(cpu);

@@ -4180,7 +4188,6 @@ void __devinit init_idle(task_t *idle, i
 #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
 	idle->oncpu = 1;
 #endif
-	set_tsk_need_resched(idle);
 	spin_unlock_irqrestore(&rq->lock, flags);
 
 	/* Set the preempt count _outside_ the spinlocks! */

@@ -383,6 +383,13 @@ static void noinline rest_init(void)
 	numa_default_policy();
 	unlock_kernel();
 	preempt_enable_no_resched();
+
+	/*
+	 * The boot idle thread must execute schedule()
+	 * at least once to get things moving:
+	 */
+	schedule();
+
 	cpu_idle();
 } 
 

@@ -4163,6 +4163,14 @@ void show_state(void)
 	read_unlock(&tasklist_lock);
 }
 
+/**
+ * init_idle - set up an idle thread for a given CPU
+ * @idle: task in question
+ * @cpu: cpu the idle task belongs to
+ *
+ * NOTE: this function does not set the idle thread's NEED_RESCHED
+ * flag, to make booting more robust.
+ */
 void __devinit init_idle(task_t *idle, int cpu)
 {
 	runqueue_t *rq = cpu_rq(cpu);

@@ -4180,7 +4188,6 @@ void __devinit init_idle(task_t *idle, i
 #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
 	idle->oncpu = 1;
 #endif
-	set_tsk_need_resched(idle);
 	spin_unlock_irqrestore(&rq->lock, flags);
 
 	/* Set the preempt count _outside_ the spinlocks! */

@@ -383,6 +383,13 @@ static void noinline rest_init(void)
 	numa_default_policy();
 	unlock_kernel();
 	preempt_enable_no_resched();
+
+	/*
+	 * The boot idle thread must execute schedule()
+	 * at least once to get things moving:
+	 */
+	schedule();
+
 	cpu_idle();
 } 
 

Index: linux-2.6/kernel/sched.c
===================================================================
@@ -845,21 +845,28 @@ static void deactivate_task(struct task_
 #ifdef CONFIG_SMP
 static void resched_task(task_t *p)
 {
-	int need_resched, nrpolling;
+	int cpu;
 
 	assert_spin_locked(&task_rq(p)->lock);
 
-	/* minimise the chance of sending an interrupt to poll_idle() */
-	nrpolling = test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
-	need_resched = test_and_set_tsk_thread_flag(p,TIF_NEED_RESCHED);
-	nrpolling |= test_tsk_thread_flag(p,TIF_POLLING_NRFLAG);
+	if (unlikely(test_tsk_thread_flag(p, TIF_NEED_RESCHED)))
+		return;
+	
+	set_tsk_thread_flag(p, TIF_NEED_RESCHED);
 
-	if (!need_resched && !nrpolling && (task_cpu(p) != smp_processor_id()))
-		smp_send_reschedule(task_cpu(p));
+	cpu = task_cpu(p);
+	if (cpu == smp_processor_id())
+		return;
+
+	/* NEED_RESCHED must be visible before we test POLLING_NRFLAG */
+	smp_mb();
+	if (!test_tsk_thread_flag(p, TIF_POLLING_NRFLAG))
+		smp_send_reschedule(cpu);
 }
 #else
 static inline void resched_task(task_t *p)
 {
+	assert_spin_locked(&task_rq(p)->lock);
 	set_tsk_need_resched(p);
 }
 #endif

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Index: linux-2.6/init/main.c
===================================================================
@@ -382,13 +382,14 @@ static void noinline rest_init(void)
 	kernel_thread(init, NULL, CLONE_FS | CLONE_SIGHAND);
 	numa_default_policy();
 	unlock_kernel();
-	preempt_enable_no_resched();
 
 	/*
 	 * The boot idle thread must execute schedule()
 	 * at least once to get things moving:
 	 */
+	preempt_enable_no_resched();
 	schedule();
+	preempt_disable();
 
 	cpu_idle();
 } 

Index: linux-2.6/arch/i386/kernel/apm.c
===================================================================
@@ -767,8 +767,20 @@ static int set_system_power_state(u_shor
 static int apm_do_idle(void)
 {
 	u32	eax;
+	u8	ret;
+	int	idled = 0;
 
-	if (apm_bios_call_simple(APM_FUNC_IDLE, 0, 0, &eax)) {
+	clear_thread_flag(TIF_POLLING_NRFLAG);
+	smp_mb__after_clear_bit();
+	if (!need_resched()) {
+		idled = 1;
+		ret = apm_bios_call_simple(APM_FUNC_IDLE, 0, 0, &eax);
+	}
+	set_thread_flag(TIF_POLLING_NRFLAG);
+	if (!idled)
+		return 0;
+
+	if (ret) {
 		static unsigned long t;
 
 		/* This always fails on some SMP boards running UP kernels.

Index: linux-2.6/drivers/acpi/processor_idle.c
===================================================================
@@ -164,6 +164,14 @@ acpi_processor_power_activate (
 	return;
 }
 
+static void acpi_safe_halt (void)
+{
+	clear_thread_flag(TIF_POLLING_NRFLAG);
+	smp_mb__after_clear_bit();
+	while (!need_resched())
+		safe_halt();
+	set_thread_flag(TIF_POLLING_NRFLAG);
+}
 
 static atomic_t 	c3_cpu_count;
 

@@ -176,7 +184,7 @@ static void acpi_processor_idle (void)
 	int			sleep_ticks = 0;
 	u32			t1, t2 = 0;
 
-	pr = processors[_smp_processor_id()];
+	pr = processors[smp_processor_id()];
 	if (!pr)
 		return;
 

@@ -196,8 +204,13 @@ static void acpi_processor_idle (void)
 	}
 
 	cx = pr->power.state;
-	if (!cx)
-		goto easy_out;
+	if (!cx) {
+		if (pm_idle_save)
+			pm_idle_save();
+		else
+			acpi_safe_halt();
+		return;
+	}
 
 	/*
 	 * Check BM Activity

@@ -277,7 +290,8 @@ static void acpi_processor_idle (void)
 		if (pm_idle_save)
 			pm_idle_save();
 		else
-			safe_halt();
+			acpi_safe_halt();
+
 		/*
                  * TBD: Can't get time duration while in C1, as resumes
 		 *      go to an ISR rather than here.  Need to instrument

@@ -407,16 +421,6 @@ end:
 	 */
 	if (next_state != pr->power.state)
 		acpi_processor_power_activate(pr, next_state);
-
-	return;
-
- easy_out:
-	/* do C1 instead of busy loop */
-	if (pm_idle_save)
-		pm_idle_save();
-	else
-		safe_halt();
-	return;
 }
 
 

Index: linux-2.6/arch/i386/kernel/smpboot.c
===================================================================
@@ -477,6 +477,8 @@ set_cpu_sibling_map(int cpu)
  */
 static void __devinit start_secondary(void *unused)
 {
+	preempt_disable();
+
 	/*
 	 * Dont put anything before smp_callin(), SMP
 	 * booting is too fragile that we want to limit the

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272 lines not on this page · raw message

Index: linux-2.6/arch/ia64/kernel/process.c
===================================================================
@@ -195,11 +195,16 @@ update_pal_halt_status(int status)
 void
 default_idle (void)
 {
-	while (!need_resched())
-		if (can_do_pal_halt)
+	if (can_do_pal_halt) {
+		clear_thread_flag(TIF_POLLING_NRFLAG);
+		smp_mb__after_clear_bit();
+		while (!need_resched())
 			safe_halt();
-		else
+		set_thread_flag(TIF_POLLING_NRFLAG);
+	} else {
+		while (!need_resched())
 			cpu_relax();
+	}
 }
 
 #ifdef CONFIG_HOTPLUG_CPU

@@ -261,16 +266,16 @@ void __attribute__((noreturn))
 cpu_idle (void)
 {
 	void (*mark_idle)(int) = ia64_mark_idle;
+  	int cpu = smp_processor_id();
+	set_thread_flag(TIF_POLLING_NRFLAG);
 
 	/* endless idle loop with no priority at all */
 	while (1) {
+		if (!need_resched()) {
+			void (*idle)(void);
 #ifdef CONFIG_SMP
-		if (!need_resched())
 			min_xtp();
 #endif
-		while (!need_resched()) {
-			void (*idle)(void);
-
 			if (__get_cpu_var(cpu_idle_state))
 				__get_cpu_var(cpu_idle_state) = 0;
 

@@ -282,17 +287,17 @@ cpu_idle (void)
 			if (!idle)
 				idle = default_idle;
 			(*idle)();
-		}
-
-		if (mark_idle)
-			(*mark_idle)(0);
-
+			if (mark_idle)
+				(*mark_idle)(0);
 #ifdef CONFIG_SMP
-		normal_xtp();
+			normal_xtp();
 #endif
+		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
-		if (cpu_is_offline(smp_processor_id()))
+		if (cpu_is_offline(cpu))
 			play_dead();
 	}
 }

Index: linux-2.6/arch/ia64/kernel/smpboot.c
===================================================================
@@ -393,6 +393,8 @@ smp_callin (void)
 int __devinit
 start_secondary (void *unused)
 {
+	preempt_disable();
+
 	/* Early console may use I/O ports */
 	ia64_set_kr(IA64_KR_IO_BASE, __pa(ia64_iobase));
 	Dprintk("start_secondary: starting CPU 0x%x\n", hard_smp_processor_id());

Index: linux-2.6/arch/ppc64/kernel/smp.c
===================================================================
@@ -561,7 +561,10 @@ int __devinit __cpu_up(unsigned int cpu)
 /* Activate a secondary processor. */
 int __devinit start_secondary(void *unused)
 {
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
+	
+	preempt_disable();
+	cpu = smp_processor_id();
 
 	atomic_inc(&init_mm.mm_count);
 	current->active_mm = &init_mm;

Index: linux-2.6/arch/sparc64/kernel/smp.c
===================================================================
@@ -144,6 +144,9 @@ void __init smp_callin(void)
 		membar("#LoadLoad");
 
 	cpu_set(cpuid, cpu_online_map);
+
+	/* idle thread is expected to have preempt disabled */
+	preempt_disable();
 }
 
 void cpu_panic(void)

@@ -1167,20 +1170,9 @@ void __init smp_cpus_done(unsigned int m
 	       (bogosum/(5000/HZ))%100);
 }
 
-/* This needn't do anything as we do not sleep the cpu
- * inside of the idler task, so an interrupt is not needed
- * to get a clean fast response.
- *
- * XXX Reverify this assumption... -DaveM
- *
- * Addendum: We do want it to do something for the signal
- *           delivery case, we detect that by just seeing
- *           if we are trying to send this to an idler or not.
- */
 void smp_send_reschedule(int cpu)
 {
-	if (cpu_data(cpu).idle_volume == 0)
-		smp_receive_signal(cpu);
+	smp_receive_signal(cpu);
 }
 
 /* This is a nop because we capture all other cpus

Index: linux-2.6/arch/sparc64/kernel/process.c
===================================================================
@@ -74,7 +74,9 @@ void cpu_idle(void)
 		while (!need_resched())
 			barrier();
 
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
 	}
 }

@@ -83,21 +85,31 @@ void cpu_idle(void)
 
 /*
  * the idle loop on a UltraMultiPenguin...
+ * 
+ * TIF_POLLING_NRFLAG is set because we do not sleep the cpu
+ * inside of the idler task, so an interrupt is not needed
+ * to get a clean fast response.
+ *
+ * XXX Reverify this assumption... -DaveM
+ *
+ * Addendum: We do want it to do something for the signal
+ *           delivery case, we detect that by just seeing
+ *           if we are trying to send this to an idler or not.
  */
-#define idle_me_harder()	(cpu_data(smp_processor_id()).idle_volume += 1)
-#define unidle_me()		(cpu_data(smp_processor_id()).idle_volume = 0)
 void cpu_idle(void)
 {
+	cpuinfo_sparc *cpuinfo = &local_cpu_data();
 	set_thread_flag(TIF_POLLING_NRFLAG);
+
 	while(1) {
 		if (need_resched()) {
-			unidle_me();
-			clear_thread_flag(TIF_POLLING_NRFLAG);
+			cpuinfo->idle_volume = 0;
+			preempt_enable_no_resched();
 			schedule();
-			set_thread_flag(TIF_POLLING_NRFLAG);
+			preempt_disable();
 			check_pgt_cache();
 		}
-		idle_me_harder();
+		cpuinfo->idle_volume++;
 
 		/* The store ordering is so that IRQ handlers on
 		 * other cpus see our increasing idleness for the buddy

Index: linux-2.6/arch/alpha/kernel/process.c
===================================================================
@@ -43,22 +43,20 @@
 #include "proto.h"
 #include "pci_impl.h"
 
-void default_idle(void)
-{
-	barrier();
-}
-
 void
 cpu_idle(void)
 {
+	set_thread_flag(TIF_POLLING_NRFLAG);
+	
 	while (1) {
-		void (*idle)(void) = default_idle;
 		/* FIXME -- EV6 and LCA45 know how to power down
 		   the CPU.  */
 
 		while (!need_resched())
-			idle();
+			cpu_relax();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/alpha/kernel/smp.c
===================================================================
@@ -128,7 +128,11 @@ wait_boot_cpu_to_stop(int cpuid)
 void __init
 smp_callin(void)
 {
-	int cpuid = hard_smp_processor_id();
+	int cpuid;
+	
+	preempt_disable();
+
+	cpuid = hard_smp_processor_id();
 
 	if (cpu_test_and_set(cpuid, cpu_online_map)) {
 		printk("??, cpu 0x%x already present??\n", cpuid);

Index: linux-2.6/arch/s390/kernel/smp.c
===================================================================
@@ -528,6 +528,8 @@ extern void pfault_fini(void);
 
 int __devinit start_secondary(void *cpuvoid)
 {
+	preempt_disable();
+
         /* Setup the cpu */
         cpu_init();
         /* init per CPU timer */

Index: linux-2.6/arch/sparc/kernel/process.c
===================================================================
@@ -72,6 +72,13 @@ struct thread_info *current_set[NR_CPUS]
  */
 void default_idle(void)
 {
+	if (pm_idle) {
+		while (!need_resched())
+			(*pm_idle)();
+	} else {
+		while (!need_resched())
+			cpu_relax();
+	}
 }
 
 #ifndef CONFIG_SMP

@@ -92,12 +99,11 @@ void cpu_idle(void)
 			static unsigned long fps;
 			unsigned long now;
 			unsigned long faults;
-			unsigned long flags;
 
 			extern unsigned long sun4c_kernel_faults;
 			extern void sun4c_grow_kernel_ring(void);
 
-			local_irq_save(flags);
+			local_irq_disable();
 			now = jiffies;
 			count -= (now - last_jiffies);
 			last_jiffies = now;

@@ -113,14 +119,14 @@ void cpu_idle(void)
 					sun4c_grow_kernel_ring();
 				}
 			}
-			local_irq_restore(flags);
+			local_irq_enable();
 		}
 
-		while((!need_resched()) && pm_idle) {
-			(*pm_idle)();
-		}
+		default_idle();
 
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
 	}
 }

@@ -130,13 +136,17 @@ void cpu_idle(void)
 /* This is being executed in task 0 'user space'. */
 void cpu_idle(void)
 {
+        set_thread_flag(TIF_POLLING_NRFLAG);
+			
 	/* endless idle loop with no priority at all */
 	while(1) {
-		if(need_resched()) {
-			schedule();
-			check_pgt_cache();
-		}
-		barrier(); /* or else gcc optimizes... */
+		while (!need_resched())
+			cpu_relax();
+
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+		check_pgt_cache();
 	}
 }
 

Index: linux-2.6/arch/ppc/kernel/idle.c
===================================================================
@@ -50,8 +50,6 @@ void default_idle(void)
 		}
 #endif
 	}
-	if (need_resched())
-		schedule();
 }
 
 /*

@@ -59,11 +57,18 @@ void default_idle(void)
  */
 void cpu_idle(void)
 {
-	for (;;)
-		if (ppc_md.idle != NULL)
-			ppc_md.idle();
-		else
-			default_idle();
+	for (;;) {
+		while (need_resched()) {
+			if (ppc_md.idle != NULL)
+				ppc_md.idle();
+			else
+				default_idle();
+		}
+
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 #if defined(CONFIG_SYSCTL) && defined(CONFIG_6xx)

Index: linux-2.6/arch/m32r/kernel/process.c
===================================================================
@@ -104,7 +104,9 @@ void cpu_idle (void)
 
 			idle();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/frv/kernel/process.c
===================================================================
@@ -77,16 +77,20 @@ void (*idle)(void) = core_sleep_idle;
  */
 void cpu_idle(void)
 {
+	int cpu = smp_processor_id();
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched()) {
-			irq_stat[smp_processor_id()].idle_timestamp = jiffies;
+			irq_stat[cpu].idle_timestamp = jiffies;
 
 			if (!frv_dma_inprogress && idle)
 				idle();
 		}
-
+		
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/cris/kernel/process.c
===================================================================
@@ -201,7 +201,9 @@ void cpu_idle (void)
 
 			idle();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 
 }

Index: linux-2.6/arch/mips/kernel/smp.c
===================================================================
@@ -83,7 +83,11 @@ extern ATTRIB_NORET void cpu_idle(void);
  */
 asmlinkage void start_secondary(void)
 {
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
+
+	preempt_disable();
+	
+	cpu = smp_processor_id();
 
 	cpu_probe();
 	cpu_report();

Index: linux-2.6/arch/parisc/kernel/process.c
===================================================================
@@ -88,11 +88,15 @@ void default_idle(void)
  */
 void cpu_idle(void)
 {
+	set_thread_flag(TIF_POLLING_NRFLAG);
+	
 	/* endless idle loop with no priority at all */
 	while (1) {
 		while (!need_resched())
 			barrier();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
 	}
 }

Index: linux-2.6/arch/ppc/kernel/smp.c
===================================================================
@@ -326,6 +326,8 @@ int __devinit start_secondary(void *unus
 {
 	int cpu;
 
+	preempt_disable();
+
 	atomic_inc(&init_mm.mm_count);
 	current->active_mm = &init_mm;
 

Index: linux-2.6/arch/sh/kernel/process.c
===================================================================
@@ -51,28 +51,24 @@ void enable_hlt(void)
 
 EXPORT_SYMBOL(enable_hlt);
 
-void default_idle(void)
+void cpu_idle(void)
 {
 	/* endless idle loop with no priority at all */
 	while (1) {
 		if (hlt_counter) {
-			while (1)
-				if (need_resched())
-					break;
+			while (!need_resched())
+				cpu_relax();
 		} else {
 			while (!need_resched())
 				cpu_sleep();
 		}
 
+		preempt_disable_no_resched();
 		schedule();
+		preempt_enable();
 	}
 }
 
-void cpu_idle(void)
-{
-	default_idle();
-}
-
 void machine_restart(char * __unused)
 {
 	/* SR.BL=1 and invoke address error to let CPU reset (manual reset) */

Index: linux-2.6/arch/m68k/kernel/process.c
===================================================================
@@ -102,7 +102,9 @@ void cpu_idle(void)
 	while (1) {
 		while (!need_resched())
 			idle();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/mips/kernel/process.c
===================================================================
@@ -58,7 +58,9 @@ ATTRIB_NORET void cpu_idle(void)
 		while (!need_resched())
 			if (cpu_wait)
 				(*cpu_wait)();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable()
 	}
 }
 

Index: linux-2.6/arch/m68knommu/kernel/process.c
===================================================================
@@ -45,11 +45,8 @@ asmlinkage void ret_from_fork(void);
  */
 void default_idle(void)
 {
-	while(1) {
-		if (need_resched())
-			__asm__("stop #0x2000" : : : "cc");
-		schedule();
-	}
+	while (!need_resched())
+		__asm__("stop #0x2000" : : : "cc");
 }
 
 void (*idle)(void) = default_idle;

@@ -63,7 +60,12 @@ void (*idle)(void) = default_idle;
 void cpu_idle(void)
 {
 	/* endless idle loop with no priority at all */
-	idle();
+	while (1) {
+		idle();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 void machine_restart(char * __unused)

Index: linux-2.6/arch/sh/kernel/smp.c
===================================================================
@@ -109,7 +109,11 @@ int __cpu_up(unsigned int cpu)
 
 int start_secondary(void *unused)
 {
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
+	
+	preempt_disable();
+	
+	cpu = smp_processor_id();
 
 	atomic_inc(&init_mm.mm_count);
 	current->active_mm = &init_mm;

Index: linux-2.6/arch/parisc/kernel/smp.c
===================================================================
@@ -462,6 +462,8 @@ void __init smp_callin(void)
 	void *istack;
 #endif
 
+	preempt_disable();
+
 	smp_cpu_init(slave_id);
 
 #if 0	/* NOT WORKING YET - see entry.S */

Index: linux-2.6/arch/m32r/kernel/smpboot.c
===================================================================
@@ -424,6 +424,7 @@ void __init smp_cpus_done(unsigned int m
  *==========================================================================*/
 int __init start_secondary(void *unused)
 {
+	preempt_disable();
 	cpu_init();
 	smp_callin();
 	while (!cpu_isset(smp_processor_id(), smp_commenced_mask))

Index: linux-2.6/arch/s390/kernel/process.c
===================================================================
@@ -101,11 +101,6 @@ void default_idle(void)
 	int cpu, rc;
 
 	local_irq_disable();
-        if (need_resched()) {
-		local_irq_enable();
-                schedule();
-                return;
-        }
 
 	/* CPU is going idle. */
 	cpu = smp_processor_id();

@@ -121,7 +116,7 @@ void default_idle(void)
 	__ctl_set_bit(8, 15);
 
 #ifdef CONFIG_HOTPLUG_CPU
-	if (cpu_is_offline(smp_processor_id()))
+	if (cpu_is_offline(cpu))
 		cpu_die();
 #endif
 

@@ -161,8 +156,13 @@ void default_idle(void)
 
 void cpu_idle(void)
 {
-	for (;;)
-		default_idle();
+	for (;;) {
+		while (!need_resched())
+			default_idle();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 void show_regs(struct pt_regs *regs)

Index: linux-2.6/arch/sh64/kernel/process.c
===================================================================
@@ -307,23 +307,19 @@ __setup("hlt", hlt_setup);
 
 static inline void hlt(void)
 {
-	if (hlt_counter)
-		return;
-
 	__asm__ __volatile__ ("sleep" : : : "memory");
 }
 
 /*
  * The idle loop on a uniprocessor SH..
  */
-void default_idle(void)
+void cpu_idle(void)
 {
 	/* endless idle loop with no priority at all */
 	while (1) {
 		if (hlt_counter) {
-			while (1)
-				if (need_resched())
-					break;
+			while (!need_resched())
+				cpu_relax();
 		} else {
 			local_irq_disable();
 			while (!need_resched()) {

@@ -334,13 +330,11 @@ void default_idle(void)
 			}
 			local_irq_enable();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
-}
 
-void cpu_idle(void)
-{
-	default_idle();
 }
 
 void machine_restart(char * __unused)

Index: linux-2.6/arch/arm26/kernel/process.c
===================================================================
@@ -74,15 +74,13 @@ __setup("hlt", hlt_setup);
 void cpu_idle(void)
 {
 	/* endless idle loop with no priority at all */
-	preempt_disable();
 	while (1) {
-		while (!need_resched()) {
-			local_irq_disable();
-			if (!need_resched() && !hlt_counter)
-				local_irq_enable();
-		}
+		while (!need_resched())
+			cpu_relax();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
 	}
-	schedule();
 }
 
 static char reboot_mode = 'h';

Index: linux-2.6/arch/arm/kernel/process.c
===================================================================
@@ -84,10 +84,14 @@ EXPORT_SYMBOL(pm_power_off);
  */
 void default_idle(void)
 {
-	local_irq_disable();
-	if (!need_resched() && !hlt_counter)
-		arch_idle();
-	local_irq_enable();
+	if (hlt_counter)
+		cpu_relax()
+	else {
+		local_irq_disable();
+		if (!need_resched())
+			arch_idle();
+		local_irq_enable();
+	}
 }
 
 /*

@@ -104,13 +108,13 @@ void cpu_idle(void)
 		void (*idle)(void) = pm_idle;
 		if (!idle)
 			idle = default_idle;
-		preempt_disable();
 		leds_event(led_idle_start);
 		while (!need_resched())
 			idle();
 		leds_event(led_idle_end);
-		preempt_enable();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/h8300/kernel/process.c
===================================================================
@@ -53,22 +53,17 @@ asmlinkage void ret_from_fork(void);
 #if !defined(CONFIG_H8300H_SIM) && !defined(CONFIG_H8S_SIM)
 void default_idle(void)
 {
-	while(1) {
-		if (need_resched()) {
-			local_irq_enable();
-			__asm__("sleep");
-			local_irq_disable();
-		}
-		schedule();
+	local_irq_disable();
+	if (need_resched()) {
+		local_irq_enable();
+		/* XXX: race here! What if need_resched() gets set now? */
+		__asm__("sleep");
 	}
 }
 #else
 void default_idle(void)
 {
-	while(1) {
-		if (need_resched())
-			schedule();
-	}
+	cpu_relax();
 }
 #endif
 void (*idle)(void) = default_idle;

@@ -81,7 +76,13 @@ void (*idle)(void) = default_idle;
  */
 void cpu_idle(void)
 {
-	idle();
+	while (1) {
+		while (!need_resched())
+			idle();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 void machine_restart(char * __unused)

Index: linux-2.6/arch/xtensa/kernel/process.c
===================================================================
@@ -96,8 +96,9 @@ void cpu_idle(void)
 	while (1) {
 		while (!need_resched())
 			platform_idle();
-		preempt_enable();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 

Index: linux-2.6/arch/v850/kernel/process.c
===================================================================
@@ -36,11 +36,8 @@ extern void ret_from_fork (void);
 /* The idle loop.  */
 void default_idle (void)
 {
-	while (1) {
-		while (! need_resched ())
-			asm ("halt; nop; nop; nop; nop; nop" ::: "cc");
-		schedule ();
-	}
+	while (! need_resched ())
+		asm ("halt; nop; nop; nop; nop; nop" ::: "cc");
 }
 
 void (*idle)(void) = default_idle;

@@ -54,7 +51,14 @@ void (*idle)(void) = default_idle;
 void cpu_idle (void)
 {
 	/* endless idle loop with no priority at all */
-	(*idle) ();
+	while (1) {
+		while (!need_resched())
+			(*idle) ();
+
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
 }
 
 /*