Merge branches 'doc.2015.02.26a', 'earlycb.2015.03.03a', 'fixes.2015.…

…03.03a', 'gpexp.2015.02.26a', 'hotplug.2015.03.20a', 'sysidle.2015.02.26b' and 'tiny.2015.02.26a' into HEAD

doc.2015.02.26a:  Documentation changes
earlycb.2015.03.03a:  Permit early-boot RCU callbacks
fixes.2015.03.03a:  Miscellaneous fixes
gpexp.2015.02.26a:  In-kernel expediting of normal grace periods
hotplug.2015.03.20a:  CPU hotplug fixes
sysidle.2015.02.26b:  NO_HZ_FULL_SYSIDLE fixes
tiny.2015.02.26a:  TINY_RCU fixes

Documentation/kernel-parameters.txt

@@ -2968,6 +2968,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Set maximum number of finished RCU callbacks to
 			process in one batch.
 
+	rcutree.gp_init_delay=	[KNL]
+			Set the number of jiffies to delay each step of
+			RCU grace-period initialization.  This only has
+			effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
+			set.
+
 	rcutree.rcu_fanout_leaf= [KNL]
 			Increase the number of CPUs assigned to each
 			leaf rcu_node structure.  Useful for very large

arch/blackfin/mach-common/smp.c

@@ -413,16 +413,14 @@ int __cpu_disable(void)
 	return 0;
 }
 
-static DECLARE_COMPLETION(cpu_killed);
-
 int __cpu_die(unsigned int cpu)
 {
-	return wait_for_completion_timeout(&cpu_killed, 5000);
+	return cpu_wait_death(cpu, 5);
 }
 
 void cpu_die(void)
 {
-	complete(&cpu_killed);
+	(void)cpu_report_death();
 
 	atomic_dec(&init_mm.mm_users);
 	atomic_dec(&init_mm.mm_count);

arch/metag/kernel/smp.c

@@ -261,7 +261,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
-static DECLARE_COMPLETION(cpu_killed);
 
 /*
  * __cpu_disable runs on the processor to be shutdown.
@@ -299,7 +298,7 @@ int __cpu_disable(void)
  */
 void __cpu_die(unsigned int cpu)
 {
-	if (!wait_for_completion_timeout(&cpu_killed, msecs_to_jiffies(1)))
+	if (!cpu_wait_death(cpu, 1))
 		pr_err("CPU%u: unable to kill\n", cpu);
 }
 
@@ -314,7 +313,7 @@ void cpu_die(void)
 	local_irq_disable();
 	idle_task_exit();
 
-	complete(&cpu_killed);
+	(void)cpu_report_death();
 
 	asm ("XOR	TXENABLE, D0Re0,D0Re0\n");
 }

arch/x86/include/asm/cpu.h

@@ -34,8 +34,6 @@ extern int _debug_hotplug_cpu(int cpu, int action);
 #endif
 #endif
 
-DECLARE_PER_CPU(int, cpu_state);
-
 int mwait_usable(const struct cpuinfo_x86 *);
 
 #endif /* _ASM_X86_CPU_H */

arch/x86/include/asm/smp.h

@@ -150,12 +150,12 @@ static inline void arch_send_call_function_ipi_mask(const struct cpumask *mask)
 }
 
 void cpu_disable_common(void);
-void cpu_die_common(unsigned int cpu);
 void native_smp_prepare_boot_cpu(void);
 void native_smp_prepare_cpus(unsigned int max_cpus);
 void native_smp_cpus_done(unsigned int max_cpus);
 int native_cpu_up(unsigned int cpunum, struct task_struct *tidle);
 int native_cpu_disable(void);
+int common_cpu_die(unsigned int cpu);
 void native_cpu_die(unsigned int cpu);
 void native_play_dead(void);
 void play_dead_common(void);

arch/x86/kernel/smpboot.c

@@ -77,9 +77,6 @@
 #include <asm/realmode.h>
 #include <asm/misc.h>
 
-/* State of each CPU */
-DEFINE_PER_CPU(int, cpu_state) = { 0 };
-
 /* Number of siblings per CPU package */
 int smp_num_siblings = 1;
 EXPORT_SYMBOL(smp_num_siblings);
@@ -257,7 +254,7 @@ static void notrace start_secondary(void *unused)
 	lock_vector_lock();
 	set_cpu_online(smp_processor_id(), true);
 	unlock_vector_lock();
-	per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
+	cpu_set_state_online(smp_processor_id());
 	x86_platform.nmi_init();
 
 	/* enable local interrupts */
@@ -948,7 +945,10 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
 	 */
 	mtrr_save_state();
 
-	per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
+	/* x86 CPUs take themselves offline, so delayed offline is OK. */
+	err = cpu_check_up_prepare(cpu);
+	if (err && err != -EBUSY)
+		return err;
 
 	/* the FPU context is blank, nobody can own it */
 	__cpu_disable_lazy_restore(cpu);
@@ -1191,7 +1191,7 @@ void __init native_smp_prepare_boot_cpu(void)
 	switch_to_new_gdt(me);
 	/* already set me in cpu_online_mask in boot_cpu_init() */
 	cpumask_set_cpu(me, cpu_callout_mask);
-	per_cpu(cpu_state, me) = CPU_ONLINE;
+	cpu_set_state_online(me);
 }
 
 void __init native_smp_cpus_done(unsigned int max_cpus)
@@ -1318,14 +1318,10 @@ static void __ref remove_cpu_from_maps(int cpu)
 	numa_remove_cpu(cpu);
 }
 
-static DEFINE_PER_CPU(struct completion, die_complete);
-
 void cpu_disable_common(void)
 {
 	int cpu = smp_processor_id();
 
-	init_completion(&per_cpu(die_complete, smp_processor_id()));
-
 	remove_siblinginfo(cpu);
 
 	/* It's now safe to remove this processor from the online map */
@@ -1349,24 +1345,27 @@ int native_cpu_disable(void)
 	return 0;
 }
 
-void cpu_die_common(unsigned int cpu)
+int common_cpu_die(unsigned int cpu)
 {
-	wait_for_completion_timeout(&per_cpu(die_complete, cpu), HZ);
-}
+	int ret = 0;
 
-void native_cpu_die(unsigned int cpu)
-{
 	/* We don't do anything here: idle task is faking death itself. */
 
-	cpu_die_common(cpu);
-
 	/* They ack this in play_dead() by setting CPU_DEAD */
-	if (per_cpu(cpu_state, cpu) == CPU_DEAD) {
+	if (cpu_wait_death(cpu, 5)) {
 		if (system_state == SYSTEM_RUNNING)
 			pr_info("CPU %u is now offline\n", cpu);
 	} else {
 		pr_err("CPU %u didn't die...\n", cpu);
+		ret = -1;
 	}
+
+	return ret;
+}
+
+void native_cpu_die(unsigned int cpu)
+{
+	common_cpu_die(cpu);
 }
 
 void play_dead_common(void)
@@ -1375,10 +1374,8 @@ void play_dead_common(void)
 	reset_lazy_tlbstate();
 	amd_e400_remove_cpu(raw_smp_processor_id());
 
-	mb();
 	/* Ack it */
-	__this_cpu_write(cpu_state, CPU_DEAD);
-	complete(&per_cpu(die_complete, smp_processor_id()));
+	(void)cpu_report_death();
 
 	/*
 	 * With physical CPU hotplug, we should halt the cpu

arch/x86/xen/smp.c

@@ -90,14 +90,10 @@ static void cpu_bringup(void)
 
 	set_cpu_online(cpu, true);
 
-	this_cpu_write(cpu_state, CPU_ONLINE);
-
-	wmb();
+	cpu_set_state_online(cpu);  /* Implies full memory barrier. */
 
 	/* We can take interrupts now: we're officially "up". */
 	local_irq_enable();
-
-	wmb();			/* make sure everything is out */
 }
 
 /*
@@ -459,7 +455,13 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
 	xen_setup_timer(cpu);
 	xen_init_lock_cpu(cpu);
 
-	per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
+	/*
+	 * PV VCPUs are always successfully taken down (see 'while' loop
+	 * in xen_cpu_die()), so -EBUSY is an error.
+	 */
+	rc = cpu_check_up_prepare(cpu);
+	if (rc)
+		return rc;
 
 	/* make sure interrupts start blocked */
 	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
@@ -479,10 +481,8 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
 	rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
 	BUG_ON(rc);
 
-	while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
+	while (cpu_report_state(cpu) != CPU_ONLINE)
 		HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
-		barrier();
-	}
 
 	return 0;
 }
@@ -511,11 +511,11 @@ static void xen_cpu_die(unsigned int cpu)
 		schedule_timeout(HZ/10);
 	}
 
-	cpu_die_common(cpu);
-
-	xen_smp_intr_free(cpu);
-	xen_uninit_lock_cpu(cpu);
-	xen_teardown_timer(cpu);
+	if (common_cpu_die(cpu) == 0) {
+		xen_smp_intr_free(cpu);
+		xen_uninit_lock_cpu(cpu);
+		xen_teardown_timer(cpu);
+	}
 }
 
 static void xen_play_dead(void) /* used only with HOTPLUG_CPU */
@@ -747,6 +747,16 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
 static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
 {
 	int rc;
+
+	/*
+	 * This can happen if CPU was offlined earlier and
+	 * offlining timed out in common_cpu_die().
+	 */
+	if (cpu_report_state(cpu) == CPU_DEAD_FROZEN) {
+		xen_smp_intr_free(cpu);
+		xen_uninit_lock_cpu(cpu);
+	}
+
 	/*
 	 * xen_smp_intr_init() needs to run before native_cpu_up()
 	 * so that IPI vectors are set up on the booting CPU before
@@ -768,20 +778,14 @@ static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
 	return rc;
 }
 
-static void xen_hvm_cpu_die(unsigned int cpu)
-{
-	xen_cpu_die(cpu);
-	native_cpu_die(cpu);
-}
-
 void __init xen_hvm_smp_init(void)
 {
 	if (!xen_have_vector_callback)
 		return;
 	smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
 	smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
 	smp_ops.cpu_up = xen_hvm_cpu_up;
-	smp_ops.cpu_die = xen_hvm_cpu_die;
+	smp_ops.cpu_die = xen_cpu_die;
 	smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
 	smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi;
 	smp_ops.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu;

include/linux/cpu.h

@@ -95,6 +95,10 @@ enum {
 					* Called on the new cpu, just before
 					* enabling interrupts. Must not sleep,
 					* must not fail */
+#define CPU_DYING_IDLE		0x000B /* CPU (unsigned)v dying, reached
+					* idle loop. */
+#define CPU_BROKEN		0x000C /* CPU (unsigned)v did not die properly,
+					* perhaps due to preemption. */
 
 /* Used for CPU hotplug events occurring while tasks are frozen due to a suspend
  * operation in progress
@@ -271,4 +275,14 @@ void arch_cpu_idle_enter(void);
 void arch_cpu_idle_exit(void);
 void arch_cpu_idle_dead(void);
 
+DECLARE_PER_CPU(bool, cpu_dead_idle);
+
+int cpu_report_state(int cpu);
+int cpu_check_up_prepare(int cpu);
+void cpu_set_state_online(int cpu);
+#ifdef CONFIG_HOTPLUG_CPU
+bool cpu_wait_death(unsigned int cpu, int seconds);
+bool cpu_report_death(void);
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+
 #endif /* _LINUX_CPU_H_ */

include/linux/lockdep.h

@@ -531,8 +531,13 @@ do {									\
 # define might_lock_read(lock) do { } while (0)
 #endif
 
-#ifdef CONFIG_PROVE_RCU
+#ifdef CONFIG_LOCKDEP
 void lockdep_rcu_suspicious(const char *file, const int line, const char *s);
+#else
+static inline void
+lockdep_rcu_suspicious(const char *file, const int line, const char *s)
+{
+}
 #endif
 
 #endif /* __LINUX_LOCKDEP_H */