From 38498a67aa2cf8c80754b8d304bfacc10bc582b5 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 20 Apr 2012 13:05:44 +0000 Subject: smp: Add generic smpboot facility Start a new file, which will hold SMP and CPU hotplug related generic infrastructure. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Rusty Russell Cc: Paul E. McKenney Cc: Srivatsa S. Bhat Cc: Matt Turner Cc: Russell King Cc: Mike Frysinger Cc: Jesper Nilsson Cc: Richard Kuo Cc: Tony Luck Cc: Hirokazu Takata Cc: Ralf Baechle Cc: David Howells Cc: James E.J. Bottomley Cc: Benjamin Herrenschmidt Cc: Martin Schwidefsky Cc: Paul Mundt Cc: David S. Miller Cc: Chris Metcalf Cc: Richard Weinberger Cc: x86@kernel.org Link: http://lkml.kernel.org/r/20120420124557.035417523@linutronix.de --- kernel/smpboot.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) create mode 100644 kernel/smpboot.c (limited to 'kernel/smpboot.c') diff --git a/kernel/smpboot.c b/kernel/smpboot.c new file mode 100644 index 000000000000..6dae6a3d2d59 --- /dev/null +++ b/kernel/smpboot.c @@ -0,0 +1,14 @@ +/* + * Common SMP CPU bringup/teardown functions + */ +#include + +#include "smpboot.h" + +/** + * smpboot_prepare - generic smpboot preparation + */ +int __cpuinit smpboot_prepare(unsigned int cpu) +{ + return 0; +} -- cgit v1.2.3 From 29d5e0476e1c4a513859e7858845ad172f560389 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 20 Apr 2012 13:05:45 +0000 Subject: smp: Provide generic idle thread allocation All SMP architectures have magic to fork the idle task and to store it for reusage when cpu hotplug is enabled. Provide a generic infrastructure for it. Create/reinit the idle thread for the cpu which is brought up in the generic code and hand the thread pointer to the architecture code via __cpu_up(). Note, that fork_idle() is called via a workqueue, because this guarantees that the idle thread does not get a reference to a user space VM. This can happen when the boot process did not bring up all possible cpus and a later cpu_up() is initiated via the sysfs interface. In that case fork_idle() would be called in the context of the user space task and take a reference on the user space VM. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: Rusty Russell Cc: Paul E. McKenney Cc: Srivatsa S. Bhat Cc: Matt Turner Cc: Russell King Cc: Mike Frysinger Cc: Jesper Nilsson Cc: Richard Kuo Cc: Tony Luck Cc: Hirokazu Takata Cc: Ralf Baechle Cc: David Howells Cc: James E.J. Bottomley Cc: Benjamin Herrenschmidt Cc: Martin Schwidefsky Cc: Paul Mundt Cc: David S. Miller Cc: Chris Metcalf Cc: Richard Weinberger Cc: x86@kernel.org Acked-by: Venkatesh Pallipadi Link: http://lkml.kernel.org/r/20120420124557.102478630@linutronix.de --- arch/Kconfig | 3 ++ kernel/cpu.c | 2 +- kernel/sched/core.c | 2 ++ kernel/smpboot.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++- kernel/smpboot.h | 10 +++++++ 5 files changed, 99 insertions(+), 2 deletions(-) (limited to 'kernel/smpboot.c') diff --git a/arch/Kconfig b/arch/Kconfig index 684eb5af439d..4f0d0f7c8313 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -145,6 +145,9 @@ config HAVE_DMA_ATTRS config USE_GENERIC_SMP_HELPERS bool +config GENERIC_SMP_IDLE_THREAD + bool + config HAVE_REGS_AND_STACK_ACCESS_API bool help diff --git a/kernel/cpu.c b/kernel/cpu.c index e58b99ada3d8..05c46bae5e55 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -316,7 +316,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) } /* Arch-specific enabling code. */ - ret = __cpu_up(cpu, NULL); + ret = __cpu_up(cpu, idle_thread_get(cpu)); if (ret != 0) goto out_notify; BUG_ON(!cpu_online(cpu)); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4603b9d8f30a..6a63cde23d03 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -83,6 +83,7 @@ #include "sched.h" #include "../workqueue_sched.h" +#include "../smpboot.h" #define CREATE_TRACE_POINTS #include @@ -7049,6 +7050,7 @@ void __init sched_init(void) /* May be allocated at isolcpus cmdline parse time */ if (cpu_isolated_map == NULL) zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT); + idle_thread_set_boot_cpu(); #endif init_sched_fair_class(); diff --git a/kernel/smpboot.c b/kernel/smpboot.c index 6dae6a3d2d59..ed1576981801 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -1,14 +1,96 @@ /* * Common SMP CPU bringup/teardown functions */ +#include +#include #include +#include +#include +#include #include "smpboot.h" +#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD +struct create_idle { + struct work_struct work; + struct task_struct *idle; + struct completion done; + unsigned int cpu; +}; + +static void __cpuinit do_fork_idle(struct work_struct *work) +{ + struct create_idle *c = container_of(work, struct create_idle, work); + + c->idle = fork_idle(c->cpu); + complete(&c->done); +} + +static struct task_struct * __cpuinit idle_thread_create(unsigned int cpu) +{ + struct create_idle c_idle = { + .cpu = cpu, + .done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done), + }; + + INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle); + schedule_work(&c_idle.work); + wait_for_completion(&c_idle.done); + destroy_work_on_stack(&c_idle.work); + return c_idle.idle; +} + +/* + * For the hotplug case we keep the task structs around and reuse + * them. + */ +static DEFINE_PER_CPU(struct task_struct *, idle_threads); + +static inline struct task_struct *get_idle_for_cpu(unsigned int cpu) +{ + struct task_struct *tsk = per_cpu(idle_threads, cpu); + + if (!tsk) + return idle_thread_create(cpu); + init_idle(tsk, cpu); + return tsk; +} + +struct task_struct * __cpuinit idle_thread_get(unsigned int cpu) +{ + return per_cpu(idle_threads, cpu); +} + +void __init idle_thread_set_boot_cpu(void) +{ + per_cpu(idle_threads, smp_processor_id()) = current; +} + +/** + * idle_thread_init - Initialize the idle thread for a cpu + * @cpu: The cpu for which the idle thread should be initialized + * + * Creates the thread if it does not exist. + */ +static int __cpuinit idle_thread_init(unsigned int cpu) +{ + struct task_struct *idle = get_idle_for_cpu(cpu); + + if (IS_ERR(idle)) { + printk(KERN_ERR "failed fork for CPU %u\n", cpu); + return PTR_ERR(idle); + } + per_cpu(idle_threads, cpu) = idle; + return 0; +} +#else +static inline int idle_thread_init(unsigned int cpu) { return 0; } +#endif + /** * smpboot_prepare - generic smpboot preparation */ int __cpuinit smpboot_prepare(unsigned int cpu) { - return 0; + return idle_thread_init(cpu); } diff --git a/kernel/smpboot.h b/kernel/smpboot.h index d88e77165086..7943bbbab917 100644 --- a/kernel/smpboot.h +++ b/kernel/smpboot.h @@ -1,6 +1,16 @@ #ifndef SMPBOOT_H #define SMPBOOT_H +struct task_struct; + int smpboot_prepare(unsigned int cpu); +#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD +struct task_struct *idle_thread_get(unsigned int cpu); +void idle_thread_set_boot_cpu(void); +#else +static inline struct task_struct *idle_thread_get(unsigned int cpu) { return NULL; } +static inline void idle_thread_set_boot_cpu(void) { } +#endif + #endif -- cgit v1.2.3 From 3bb5d2ee396aabaa4e318f17e94d13e2ee0e5a88 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Fri, 20 Apr 2012 17:08:50 -0700 Subject: smp, idle: Allocate idle thread for each possible cpu during boot percpu areas are already allocated during boot for each possible cpu. percpu idle threads can be considered as an extension of the percpu areas, and allocate them for each possible cpu during boot. This will eliminate the need for workqueue based idle thread allocation. In future we can move the idle thread area into the percpu area too. [ tglx: Moved the loop into smpboot.c and added an error check when the init code failed to allocate an idle thread for a cpu which should be onlined ] Signed-off-by: Suresh Siddha Cc: Peter Zijlstra Cc: Rusty Russell Cc: Paul E. McKenney Cc: Srivatsa S. Bhat Cc: Tejun Heo Cc: David Rientjes Cc: venki@google.com Link: http://lkml.kernel.org/r/1334966930.28674.245.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Thomas Gleixner --- kernel/cpu.c | 9 ++++--- kernel/smp.c | 4 ++++ kernel/smpboot.c | 72 +++++++++++++++----------------------------------------- kernel/smpboot.h | 2 ++ 4 files changed, 31 insertions(+), 56 deletions(-) (limited to 'kernel/smpboot.c') diff --git a/kernel/cpu.c b/kernel/cpu.c index 05c46bae5e55..0e6353cf147a 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -297,15 +297,18 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) int ret, nr_calls = 0; void *hcpu = (void *)(long)cpu; unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0; + struct task_struct *idle; if (cpu_online(cpu) || !cpu_present(cpu)) return -EINVAL; cpu_hotplug_begin(); - ret = smpboot_prepare(cpu); - if (ret) + idle = idle_thread_get(cpu); + if (IS_ERR(idle)) { + ret = PTR_ERR(idle); goto out; + } ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls); if (ret) { @@ -316,7 +319,7 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) } /* Arch-specific enabling code. */ - ret = __cpu_up(cpu, idle_thread_get(cpu)); + ret = __cpu_up(cpu, idle); if (ret != 0) goto out_notify; BUG_ON(!cpu_online(cpu)); diff --git a/kernel/smp.c b/kernel/smp.c index 2f8b10ecf759..a61294c07f3f 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -13,6 +13,8 @@ #include #include +#include "smpboot.h" + #ifdef CONFIG_USE_GENERIC_SMP_HELPERS static struct { struct list_head queue; @@ -669,6 +671,8 @@ void __init smp_init(void) { unsigned int cpu; + idle_threads_init(); + /* FIXME: This should be done in userspace --RR */ for_each_present_cpu(cpu) { if (num_online_cpus() >= setup_max_cpus) diff --git a/kernel/smpboot.c b/kernel/smpboot.c index ed1576981801..e1a797e028a3 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -6,64 +6,42 @@ #include #include #include -#include #include "smpboot.h" #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD -struct create_idle { - struct work_struct work; - struct task_struct *idle; - struct completion done; - unsigned int cpu; -}; - -static void __cpuinit do_fork_idle(struct work_struct *work) -{ - struct create_idle *c = container_of(work, struct create_idle, work); - - c->idle = fork_idle(c->cpu); - complete(&c->done); -} - -static struct task_struct * __cpuinit idle_thread_create(unsigned int cpu) -{ - struct create_idle c_idle = { - .cpu = cpu, - .done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done), - }; - - INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle); - schedule_work(&c_idle.work); - wait_for_completion(&c_idle.done); - destroy_work_on_stack(&c_idle.work); - return c_idle.idle; -} - /* * For the hotplug case we keep the task structs around and reuse * them. */ static DEFINE_PER_CPU(struct task_struct *, idle_threads); -static inline struct task_struct *get_idle_for_cpu(unsigned int cpu) +struct task_struct * __cpuinit idle_thread_get(unsigned int cpu) { struct task_struct *tsk = per_cpu(idle_threads, cpu); if (!tsk) - return idle_thread_create(cpu); + return ERR_PTR(-ENOMEM); init_idle(tsk, cpu); return tsk; } -struct task_struct * __cpuinit idle_thread_get(unsigned int cpu) +void __init idle_thread_set_boot_cpu(void) { - return per_cpu(idle_threads, cpu); + per_cpu(idle_threads, smp_processor_id()) = current; } -void __init idle_thread_set_boot_cpu(void) +static inline void idle_init(unsigned int cpu) { - per_cpu(idle_threads, smp_processor_id()) = current; + struct task_struct *tsk = per_cpu(idle_threads, cpu); + + if (!tsk) { + tsk = fork_idle(cpu); + if (IS_ERR(tsk)) + pr_err("SMP: fork_idle() failed for CPU %u\n", cpu); + else + per_cpu(idle_threads, cpu) = tsk; + } } /** @@ -72,25 +50,13 @@ void __init idle_thread_set_boot_cpu(void) * * Creates the thread if it does not exist. */ -static int __cpuinit idle_thread_init(unsigned int cpu) +void __init idle_threads_init(void) { - struct task_struct *idle = get_idle_for_cpu(cpu); + unsigned int cpu; - if (IS_ERR(idle)) { - printk(KERN_ERR "failed fork for CPU %u\n", cpu); - return PTR_ERR(idle); + for_each_possible_cpu(cpu) { + if (cpu != smp_processor_id()) + idle_init(cpu); } - per_cpu(idle_threads, cpu) = idle; - return 0; } -#else -static inline int idle_thread_init(unsigned int cpu) { return 0; } #endif - -/** - * smpboot_prepare - generic smpboot preparation - */ -int __cpuinit smpboot_prepare(unsigned int cpu) -{ - return idle_thread_init(cpu); -} diff --git a/kernel/smpboot.h b/kernel/smpboot.h index 7943bbbab917..4cfbcb8a8362 100644 --- a/kernel/smpboot.h +++ b/kernel/smpboot.h @@ -8,9 +8,11 @@ int smpboot_prepare(unsigned int cpu); #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD struct task_struct *idle_thread_get(unsigned int cpu); void idle_thread_set_boot_cpu(void); +void idle_threads_init(void); #else static inline struct task_struct *idle_thread_get(unsigned int cpu) { return NULL; } static inline void idle_thread_set_boot_cpu(void) { } +static inline void idle_threads_init(unsigned int cpu) { } #endif #endif -- cgit v1.2.3