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Subject[PATCH 2.6.14-rc1-git5] sched: disable preempt in idle tasks
This patch should hopefully fix Nigel's bug.

Split out from sched-resched-opt.patch. Tested on i386 with acpi idle
and poll idle (previous iterations tested on various other architectures).

CCed Ian because I am amazed that arm26 ever managed to reschedule
out of the idle task without this... what am I missing?

Andrew please apply

Nick

--
SUSE Labs, Novell Inc.

Run idle threads with preempt disabled.

Also corrected a bugs in arm26's cpu_idle (make it actually call schedule()).
How did it ever work before?

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/init/main.c 2005-09-22 01:04:03.000000000 +1000
@@ -394,14 +394,16 @@ 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 one to get things moving:
*/
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();

+ /* Call into cpu_idle with preempt disabled */
cpu_idle();
}

Index: linux-2.6/arch/i386/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/i386/kernel/smpboot.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/i386/kernel/smpboot.c 2005-09-22 01:04:03.000000000 +1000
@@ -478,6 +478,8 @@ 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
Index: linux-2.6/arch/ia64/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/smpboot.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/ia64/kernel/smpboot.c 2005-09-22 01:04:03.000000000 +1000
@@ -394,6 +394,8 @@ 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
===================================================================
--- linux-2.6.orig/arch/ppc64/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/ppc64/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -545,7 +545,10 @@ 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
===================================================================
--- linux-2.6.orig/arch/sparc64/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/sparc64/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -147,6 +147,9 @@ void __init smp_callin(void)
rmb();

cpu_set(cpuid, cpu_online_map);
+
+ /* idle thread is expected to have preempt disabled */
+ preempt_disable();
}

void cpu_panic(void)
Index: linux-2.6/arch/s390/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/s390/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/s390/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -531,6 +531,8 @@ 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/m32r/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/m32r/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/m32r/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -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
===================================================================
--- linux-2.6.orig/arch/frv/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/frv/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -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
===================================================================
--- linux-2.6.orig/arch/cris/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/cris/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -218,7 +218,9 @@ void cpu_idle (void)
idle = default_idle;
idle();
}
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
}
}

Index: linux-2.6/arch/mips/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/mips/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/mips/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -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/ppc/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/ppc/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/ppc/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -339,6 +339,8 @@ 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/m68k/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/m68k/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/m68k/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -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
===================================================================
--- linux-2.6.orig/arch/mips/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/mips/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -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/sh/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/sh/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/sh/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -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
===================================================================
--- linux-2.6.orig/arch/parisc/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/parisc/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -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
===================================================================
--- linux-2.6.orig/arch/m32r/kernel/smpboot.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/m32r/kernel/smpboot.c 2005-09-22 01:04:03.000000000 +1000
@@ -425,6 +425,7 @@ 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/arm26/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/arm26/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/arm26/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -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
===================================================================
--- linux-2.6.orig/arch/arm/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/arm/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -107,13 +107,13 @@ 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
===================================================================
--- linux-2.6.orig/arch/h8300/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/h8300/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -53,22 +53,18 @@ 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
+ local_irq_enable();
}
#else
void default_idle(void)
{
- while(1) {
- if (need_resched())
- schedule();
- }
+ cpu_relax();
}
#endif
void (*idle)(void) = default_idle;
@@ -81,7 +77,13 @@ 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
===================================================================
--- linux-2.6.orig/arch/xtensa/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/xtensa/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -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
===================================================================
--- linux-2.6.orig/arch/v850/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/v850/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -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();
+ }
}

/*
Index: linux-2.6/arch/ppc64/kernel/iSeries_setup.c
===================================================================
--- linux-2.6.orig/arch/ppc64/kernel/iSeries_setup.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/ppc64/kernel/iSeries_setup.c 2005-09-22 01:04:03.000000000 +1000
@@ -898,7 +898,9 @@ static int iseries_shared_idle(void)
if (hvlpevent_is_pending())
process_iSeries_events();

+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
}

return 0;
@@ -932,7 +934,9 @@ static int iseries_dedicated_idle(void)
}

ppc64_runlatch_on();
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
}

return 0;
Index: linux-2.6/arch/x86_64/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/x86_64/kernel/smpboot.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/x86_64/kernel/smpboot.c 2005-09-22 01:04:03.000000000 +1000
@@ -473,6 +473,7 @@ void __cpuinit start_secondary(void)
* booting is too fragile that we want to limit the
* things done here to the most necessary things.
*/
+ preempt_disable();
cpu_init();
smp_callin();

Index: linux-2.6/arch/arm/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/arm/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/arm/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -162,7 +162,10 @@ int __cpuinit __cpu_up(unsigned int cpu)
asmlinkage void __cpuinit secondary_start_kernel(void)
{
struct mm_struct *mm = &init_mm;
- unsigned int cpu = smp_processor_id();
+ unsigned int cpu;
+
+ preempt_disable();
+ cpu = smp_processor_id();

printk("CPU%u: Booted secondary processor\n", cpu);

Index: linux-2.6/arch/cris/arch-v32/kernel/smp.c
===================================================================
--- linux-2.6.orig/arch/cris/arch-v32/kernel/smp.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/cris/arch-v32/kernel/smp.c 2005-09-22 01:04:03.000000000 +1000
@@ -144,6 +144,8 @@ void __init smp_callin(void)
int cpu = cpu_now_booting;
reg_intr_vect_rw_mask vect_mask = {0};

+ preempt_disable();
+
/* Initialise the idle task for this CPU */
atomic_inc(&init_mm.mm_count);
current->active_mm = &init_mm;
Index: linux-2.6/arch/i386/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/i386/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/i386/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -181,7 +181,7 @@ static inline void play_dead(void)
*/
void cpu_idle(void)
{
- int cpu = raw_smp_processor_id();
+ int cpu = smp_processor_id();

/* endless idle loop with no priority at all */
while (1) {
@@ -203,7 +203,9 @@ void cpu_idle(void)
__get_cpu_var(irq_stat).idle_timestamp = jiffies;
idle();
}
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
}
}

Index: linux-2.6/arch/ia64/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/ia64/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -292,7 +292,9 @@ cpu_idle (void)
#ifdef CONFIG_SMP
normal_xtp();
#endif
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
check_pgt_cache();
if (cpu_is_offline(smp_processor_id()))
play_dead();
Index: linux-2.6/arch/parisc/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/parisc/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/parisc/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -92,7 +92,9 @@ void cpu_idle(void)
while (1) {
while (!need_resched())
barrier();
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
check_pgt_cache();
}
}
Index: linux-2.6/arch/s390/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/s390/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/s390/kernel/process.c 2005-09-22 01:05:06.000000000 +1000
@@ -102,7 +102,6 @@ void default_idle(void)
local_irq_disable();
if (need_resched()) {
local_irq_enable();
- schedule();
return;
}

@@ -139,8 +138,14 @@ 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/sh/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/sh/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/sh/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -64,7 +64,9 @@ void default_idle(void)
cpu_sleep();
}

+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
}
}

Index: linux-2.6/arch/sh64/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/sh64/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/sh64/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -334,7 +334,9 @@ void default_idle(void)
}
local_irq_enable();
}
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
}
}

Index: linux-2.6/arch/sparc/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/sparc/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -120,7 +120,9 @@ void cpu_idle(void)
(*pm_idle)();
}

+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
check_pgt_cache();
}
}
@@ -133,7 +135,9 @@ void cpu_idle(void)
/* endless idle loop with no priority at all */
while(1) {
if(need_resched()) {
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
check_pgt_cache();
}
barrier(); /* or else gcc optimizes... */
Index: linux-2.6/arch/sparc64/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/sparc64/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/sparc64/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -74,7 +74,9 @@ void cpu_idle(void)
while (!need_resched())
barrier();

+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
check_pgt_cache();
}
}
@@ -93,7 +95,9 @@ void cpu_idle(void)
if (need_resched()) {
unidle_me();
clear_thread_flag(TIF_POLLING_NRFLAG);
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
set_thread_flag(TIF_POLLING_NRFLAG);
check_pgt_cache();
}
Index: linux-2.6/arch/x86_64/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/x86_64/kernel/process.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/x86_64/kernel/process.c 2005-09-22 01:04:03.000000000 +1000
@@ -204,7 +204,9 @@ void cpu_idle (void)
idle();
}

+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
}
}

Index: linux-2.6/arch/ppc/kernel/idle.c
===================================================================
--- linux-2.6.orig/arch/ppc/kernel/idle.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/ppc/kernel/idle.c 2005-09-22 01:04:03.000000000 +1000
@@ -52,10 +52,6 @@ void default_idle(void)
}
#endif
}
- if (need_resched())
- schedule();
- if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
- cpu_die();
}

/*
@@ -63,11 +59,20 @@ void default_idle(void)
*/
void cpu_idle(void)
{
- for (;;)
+ for (;;) {
if (ppc_md.idle != NULL)
ppc_md.idle();
else
default_idle();
+ if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
+ cpu_die();
+ if (need_resched()) {
+ preempt_enable_no_resched();
+ schedule();
+ preempt_disable();
+ }
+
+ }
}

#if defined(CONFIG_SYSCTL) && defined(CONFIG_6xx)
Index: linux-2.6/arch/ppc64/kernel/pSeries_setup.c
===================================================================
--- linux-2.6.orig/arch/ppc64/kernel/pSeries_setup.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/ppc64/kernel/pSeries_setup.c 2005-09-22 01:04:03.000000000 +1000
@@ -537,7 +537,9 @@ static int pseries_dedicated_idle(void)
lpaca->lppaca.idle = 0;
ppc64_runlatch_on();

+ preempt_enable_no_resched();
schedule();
+ preempt_disable();

if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
cpu_die();
@@ -581,7 +583,9 @@ static int pseries_shared_idle(void)
lpaca->lppaca.idle = 0;
ppc64_runlatch_on();

+ preempt_enable_no_resched();
schedule();
+ preempt_disable();

if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
cpu_die();
Index: linux-2.6/arch/ppc64/kernel/idle.c
===================================================================
--- linux-2.6.orig/arch/ppc64/kernel/idle.c 2005-09-22 01:03:51.000000000 +1000
+++ linux-2.6/arch/ppc64/kernel/idle.c 2005-09-22 01:04:03.000000000 +1000
@@ -60,7 +60,9 @@ int default_idle(void)
}

ppc64_runlatch_on();
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
cpu_die();
}
@@ -78,7 +80,9 @@ int native_idle(void)

if (need_resched()) {
ppc64_runlatch_on();
+ preempt_enable_no_resched();
schedule();
+ preempt_disable();
}

if (cpu_is_offline(smp_processor_id()) &&
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