From: Nick Piggin <nickpiggin@yahoo.com.au>
Date: Wed, 9 Nov 2005 05:39:01 +0000 (-0800)
Subject: [PATCH] sched: disable preempt in idle tasks
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=5bfb5d690f36d316a5f3b4f7775fda996faa6b12;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

[PATCH] sched: disable preempt in idle tasks

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?

Might fix the CPU hotplugging hang which Nigel Cunningham noted.

We think the bug hits if the idle thread is preempted after checking
need_resched() and before going to sleep, then the CPU offlined.

After calling stop_machine_run, the CPU eventually returns from preemption and
into the idle thread and goes to sleep.  The CPU will continue executing
previous idle and have no chance to call play_dead.

By disabling preemption until we are ready to explicitly schedule, this bug is
fixed and the idle threads generally become more robust.

From: alexs <ashepard@u.washington.edu>

  PPC build fix

From: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>

  MIPS build fix

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index ba298277becd..93dd92cc12f8 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -116,13 +116,13 @@ void cpu_idle(void)
 
 		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();
 	}
 }
 
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 77e2e9ca89fa..e55ea952f7aa 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -256,7 +256,9 @@ void __cpuexit cpu_die(void)
 asmlinkage void __cpuinit secondary_start_kernel(void)
 {
 	struct mm_struct *mm = &init_mm;
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
+
+	cpu = smp_processor_id();
 
 	printk("CPU%u: Booted secondary processor\n", cpu);
 
@@ -273,6 +275,7 @@ asmlinkage void __cpuinit secondary_start_kernel(void)
 	local_flush_tlb_all();
 
 	cpu_init();
+	preempt_disable();
 
 	/*
 	 * Give the platform a chance to do its own initialisation.
diff --git a/arch/arm26/kernel/process.c b/arch/arm26/kernel/process.c
index 9eb9964d32a7..15833a0057dd 100644
--- a/arch/arm26/kernel/process.c
+++ b/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';
diff --git a/arch/cris/arch-v32/kernel/smp.c b/arch/cris/arch-v32/kernel/smp.c
index 957f551ba5ce..13867f4fad16 100644
--- a/arch/cris/arch-v32/kernel/smp.c
+++ b/arch/cris/arch-v32/kernel/smp.c
@@ -161,6 +161,7 @@ void __init smp_callin(void)
 	REG_WR(intr_vect, irq_regs[cpu], rw_mask, vect_mask);
 	unmask_irq(IPI_INTR_VECT);
 	unmask_irq(TIMER_INTR_VECT);
+	preempt_disable();
 	local_irq_enable();
 
 	cpu_set(cpu, cpu_online_map);
diff --git a/arch/cris/kernel/process.c b/arch/cris/kernel/process.c
index 949a0e40e03c..7c80afb10460 100644
--- a/arch/cris/kernel/process.c
+++ b/arch/cris/kernel/process.c
@@ -218,7 +218,9 @@ void cpu_idle (void)
 				idle = default_idle;
 			idle();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
diff --git a/arch/frv/kernel/process.c b/arch/frv/kernel/process.c
index 3001b82b1514..54a452136f00 100644
--- a/arch/frv/kernel/process.c
+++ b/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();
 	}
 }
 
diff --git a/arch/h8300/kernel/process.c b/arch/h8300/kernel/process.c
index 27f1fce64ce4..fe21adf3e75e 100644
--- a/arch/h8300/kernel/process.c
+++ b/arch/h8300/kernel/process.c
@@ -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)
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 7a14fdfd3af9..5296e284ea36 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -179,7 +179,7 @@ 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) {
@@ -201,7 +201,9 @@ void cpu_idle(void)
 			__get_cpu_var(irq_stat).idle_timestamp = jiffies;
 			idle();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 47ec76794d02..bc5a9d97466b 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -485,6 +485,7 @@ static void __devinit start_secondary(void *unused)
 	 * things done here to the most necessary things.
 	 */
 	cpu_init();
+	preempt_disable();
 	smp_callin();
 	while (!cpu_isset(smp_processor_id(), smp_commenced_mask))
 		rep_nop();
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index 051e050359e4..4c621fc3c3b9 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -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();
diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
index 400a48987124..8f44e7d2df66 100644
--- a/arch/ia64/kernel/smpboot.c
+++ b/arch/ia64/kernel/smpboot.c
@@ -399,6 +399,7 @@ start_secondary (void *unused)
 	Dprintk("start_secondary: starting CPU 0x%x\n", hard_smp_processor_id());
 	efi_map_pal_code();
 	cpu_init();
+	preempt_disable();
 	smp_callin();
 
 	cpu_idle();
diff --git a/arch/m32r/kernel/process.c b/arch/m32r/kernel/process.c
index ea13a8f4d8b0..cc4b571e5db7 100644
--- a/arch/m32r/kernel/process.c
+++ b/arch/m32r/kernel/process.c
@@ -104,7 +104,9 @@ void cpu_idle (void)
 
 			idle();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
diff --git a/arch/m32r/kernel/smpboot.c b/arch/m32r/kernel/smpboot.c
index 640d592ea072..b90c54169fa5 100644
--- a/arch/m32r/kernel/smpboot.c
+++ b/arch/m32r/kernel/smpboot.c
@@ -426,6 +426,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
 int __init start_secondary(void *unused)
 {
 	cpu_init();
+	preempt_disable();
 	smp_callin();
 	while (!cpu_isset(smp_processor_id(), smp_commenced_mask))
 		cpu_relax();
diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c
index 11b1b90ba6ba..13d109328a42 100644
--- a/arch/m68k/kernel/process.c
+++ b/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();
 	}
 }
 
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 4fe3d5715c41..dd725779d91f 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -52,7 +52,9 @@ ATTRIB_NORET void cpu_idle(void)
 		while (!need_resched())
 			if (cpu_wait)
 				(*cpu_wait)();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index fcacf1aae98a..25472fcaf715 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -82,7 +82,7 @@ extern ATTRIB_NORET void cpu_idle(void);
  */
 asmlinkage void start_secondary(void)
 {
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
 
 	cpu_probe();
 	cpu_report();
@@ -95,6 +95,8 @@ asmlinkage void start_secondary(void)
 	 */
 
 	calibrate_delay();
+	preempt_disable();
+	cpu = smp_processor_id();
 	cpu_data[cpu].udelay_val = loops_per_jiffy;
 
 	prom_smp_finish();
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 7fdca87ef647..f482f78de435 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -92,7 +92,9 @@ void cpu_idle(void)
 	while (1) {
 		while (!need_resched())
 			barrier();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		check_pgt_cache();
 	}
 }
diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index 5db3be4e2704..a9ecf6465784 100644
--- a/arch/parisc/kernel/smp.c
+++ b/arch/parisc/kernel/smp.c
@@ -463,6 +463,7 @@ void __init smp_callin(void)
 #endif
 
 	smp_cpu_init(slave_id);
+	preempt_disable();
 
 #if 0	/* NOT WORKING YET - see entry.S */
 	istack = (void *)__get_free_pages(GFP_KERNEL,ISTACK_ORDER);
diff --git a/arch/powerpc/platforms/iseries/setup.c b/arch/powerpc/platforms/iseries/setup.c
index d3e4bf756c83..0130f2619dac 100644
--- a/arch/powerpc/platforms/iseries/setup.c
+++ b/arch/powerpc/platforms/iseries/setup.c
@@ -694,7 +694,9 @@ static void iseries_shared_idle(void)
 		if (hvlpevent_is_pending())
 			process_iSeries_events();
 
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
@@ -726,7 +728,9 @@ static void iseries_dedicated_idle(void)
 		}
 
 		ppc64_runlatch_on();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index e78c39368841..4854f5eb5c3d 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -539,7 +539,9 @@ static void 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();
@@ -583,7 +585,9 @@ static void 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();
diff --git a/arch/ppc/kernel/idle.c b/arch/ppc/kernel/idle.c
index 11e5b44713f7..a6141f05c919 100644
--- a/arch/ppc/kernel/idle.c
+++ b/arch/ppc/kernel/idle.c
@@ -53,10 +53,6 @@ void default_idle(void)
 		}
 #endif
 	}
-	if (need_resched())
-		schedule();
-	if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
-		cpu_die();
 }
 
 /*
@@ -64,11 +60,22 @@ void default_idle(void)
  */
 void cpu_idle(void)
 {
-	for (;;)
+	int cpu = smp_processor_id();
+
+	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)
diff --git a/arch/ppc/kernel/smp.c b/arch/ppc/kernel/smp.c
index bc5bf1124836..43b8fc2ca591 100644
--- a/arch/ppc/kernel/smp.c
+++ b/arch/ppc/kernel/smp.c
@@ -341,6 +341,7 @@ int __devinit start_secondary(void *unused)
 	cpu = smp_processor_id();
         smp_store_cpu_info(cpu);
 	set_dec(tb_ticks_per_jiffy);
+	preempt_disable();
 	cpu_callin_map[cpu] = 1;
 
 	printk("CPU %d done callin...\n", cpu);
diff --git a/arch/ppc64/kernel/idle.c b/arch/ppc64/kernel/idle.c
index 8fec27469802..909ea669af91 100644
--- a/arch/ppc64/kernel/idle.c
+++ b/arch/ppc64/kernel/idle.c
@@ -61,7 +61,9 @@ void default_idle(void)
 		}
 
 		ppc64_runlatch_on();
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 		if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)
 			cpu_die();
 	}
@@ -77,7 +79,9 @@ void native_idle(void)
 
 		if (need_resched()) {
 			ppc64_runlatch_on();
+			preempt_enable_no_resched();
 			schedule();
+			preempt_disable();
 		}
 
 		if (cpu_is_offline(smp_processor_id()) &&
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 9f3dff6c0b72..66ca5757e368 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -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)
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index e13c87b446b2..5856b3fda6bf 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -533,6 +533,7 @@ int __devinit start_secondary(void *cpuvoid)
 {
         /* Setup the cpu */
         cpu_init();
+	preempt_disable();
         /* init per CPU timer */
         init_cpu_timer();
 #ifdef CONFIG_VIRT_TIMER
diff --git a/arch/sh/kernel/process.c b/arch/sh/kernel/process.c
index 6dce9d0b81f8..1cbc26b796ad 100644
--- a/arch/sh/kernel/process.c
+++ b/arch/sh/kernel/process.c
@@ -64,7 +64,9 @@ void default_idle(void)
 				cpu_sleep();
 		}
 
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
index 5ecefc02896a..59e49b18252c 100644
--- a/arch/sh/kernel/smp.c
+++ b/arch/sh/kernel/smp.c
@@ -112,7 +112,9 @@ int __cpu_up(unsigned int cpu)
 
 int start_secondary(void *unused)
 {
-	unsigned int cpu = smp_processor_id();
+	unsigned int cpu;
+
+	cpu = smp_processor_id();
 
 	atomic_inc(&init_mm.mm_count);
 	current->active_mm = &init_mm;
@@ -120,6 +122,7 @@ int start_secondary(void *unused)
 	smp_store_cpu_info(cpu);
 
 	__smp_slave_init(cpu);
+	preempt_disable();
 	per_cpu_trap_init();
 	
 	atomic_inc(&cpus_booted);
diff --git a/arch/sh64/kernel/process.c b/arch/sh64/kernel/process.c
index efde41c0cd66..0c09537449b3 100644
--- a/arch/sh64/kernel/process.c
+++ b/arch/sh64/kernel/process.c
@@ -334,7 +334,9 @@ void default_idle(void)
 			}
 			local_irq_enable();
 		}
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
diff --git a/arch/sparc/kernel/process.c b/arch/sparc/kernel/process.c
index 29e72b57d4fd..c39f4d01096d 100644
--- a/arch/sparc/kernel/process.c
+++ b/arch/sparc/kernel/process.c
@@ -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... */
diff --git a/arch/sparc64/kernel/process.c b/arch/sparc64/kernel/process.c
index 7d10b0397091..2f89206e008f 100644
--- a/arch/sparc64/kernel/process.c
+++ b/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();
 	}
 }
@@ -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();
 		}
diff --git a/arch/sparc64/kernel/smp.c b/arch/sparc64/kernel/smp.c
index 5d90ee9aebf1..8aca4b1dc04e 100644
--- a/arch/sparc64/kernel/smp.c
+++ b/arch/sparc64/kernel/smp.c
@@ -168,6 +168,9 @@ 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)
diff --git a/arch/v850/kernel/process.c b/arch/v850/kernel/process.c
index 9c708c32c1f0..39cf247cdae4 100644
--- a/arch/v850/kernel/process.c
+++ b/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();
+	}
 }
 
 /*
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c
index b5a89c0bdf59..571f9fe490ce 100644
--- a/arch/x86_64/kernel/process.c
+++ b/arch/x86_64/kernel/process.c
@@ -204,7 +204,9 @@ void cpu_idle (void)
 			idle();
 		}
 
+		preempt_enable_no_resched();
 		schedule();
+		preempt_disable();
 	}
 }
 
diff --git a/arch/x86_64/kernel/smpboot.c b/arch/x86_64/kernel/smpboot.c
index 4b5b088ec102..c4e59bbdc187 100644
--- a/arch/x86_64/kernel/smpboot.c
+++ b/arch/x86_64/kernel/smpboot.c
@@ -472,6 +472,7 @@ void __cpuinit start_secondary(void)
 	 * things done here to the most necessary things.
 	 */
 	cpu_init();
+	preempt_disable();
 	smp_callin();
 
 	/* otherwise gcc will move up the smp_processor_id before the cpu_init */
diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c
index 08ef6d82ee51..6a44b54ae817 100644
--- a/arch/xtensa/kernel/process.c
+++ b/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();
 	}
 }
 
diff --git a/init/main.c b/init/main.c
index f142d4035341..27f97f9b4636 100644
--- a/init/main.c
+++ b/init/main.c
@@ -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();
 }