From 86ef5c9a8edd78e6bf92879f32329d89b2d55b5a Mon Sep 17 00:00:00 2001 From: Gautham R Shenoy Date: Fri, 25 Jan 2008 21:08:02 +0100 Subject: [PATCH] cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus() Replace all lock_cpu_hotplug/unlock_cpu_hotplug from the kernel and use get_online_cpus and put_online_cpus instead as it highlights the refcount semantics in these operations. The new API guarantees protection against the cpu-hotplug operation, but it doesn't guarantee serialized access to any of the local data structures. Hence the changes needs to be reviewed. In case of pseries_add_processor/pseries_remove_processor, use cpu_maps_update_begin()/cpu_maps_update_done() as we're modifying the cpu_present_map there. Signed-off-by: Gautham R Shenoy Signed-off-by: Ingo Molnar --- Documentation/cpu-hotplug.txt | 11 ++++++----- arch/mips/kernel/mips-mt-fpaff.c | 10 +++++----- arch/powerpc/platforms/pseries/hotplug-cpu.c | 8 ++++---- arch/powerpc/platforms/pseries/rtasd.c | 8 ++++---- arch/x86/kernel/cpu/mtrr/main.c | 8 ++++---- arch/x86/kernel/microcode.c | 16 ++++++++-------- drivers/lguest/x86/core.c | 8 ++++---- drivers/s390/char/sclp_config.c | 4 ++-- include/linux/cpu.h | 8 ++++---- kernel/cpu.c | 10 +++++----- kernel/cpuset.c | 14 +++++++------- kernel/rcutorture.c | 6 +++--- kernel/sched.c | 4 ++-- kernel/stop_machine.c | 4 ++-- net/core/flow.c | 4 ++-- 15 files changed, 62 insertions(+), 61 deletions(-) diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index a741f658a3..fb94f5a71b 100644 --- a/Documentation/cpu-hotplug.txt +++ b/Documentation/cpu-hotplug.txt @@ -109,12 +109,13 @@ Never use anything other than cpumask_t to represent bitmap of CPUs. for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask. #include - lock_cpu_hotplug() and unlock_cpu_hotplug(): + get_online_cpus() and put_online_cpus(): -The above calls are used to inhibit cpu hotplug operations. While holding the -cpucontrol mutex, cpu_online_map will not change. If you merely need to avoid -cpus going away, you could also use preempt_disable() and preempt_enable() -for those sections. Just remember the critical section cannot call any +The above calls are used to inhibit cpu hotplug operations. While the +cpu_hotplug.refcount is non zero, the cpu_online_map will not change. +If you merely need to avoid cpus going away, you could also use +preempt_disable() and preempt_enable() for those sections. +Just remember the critical section cannot call any function that can sleep or schedule this process away. The preempt_disable() will work as long as stop_machine_run() is used to take a cpu down. diff --git a/arch/mips/kernel/mips-mt-fpaff.c b/arch/mips/kernel/mips-mt-fpaff.c index 892665bb12..bb4f00c0cb 100644 --- a/arch/mips/kernel/mips-mt-fpaff.c +++ b/arch/mips/kernel/mips-mt-fpaff.c @@ -58,13 +58,13 @@ asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len, if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask))) return -EFAULT; - lock_cpu_hotplug(); + get_online_cpus(); read_lock(&tasklist_lock); p = find_process_by_pid(pid); if (!p) { read_unlock(&tasklist_lock); - unlock_cpu_hotplug(); + put_online_cpus(); return -ESRCH; } @@ -106,7 +106,7 @@ asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len, out_unlock: put_task_struct(p); - unlock_cpu_hotplug(); + put_online_cpus(); return retval; } @@ -125,7 +125,7 @@ asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len, if (len < real_len) return -EINVAL; - lock_cpu_hotplug(); + get_online_cpus(); read_lock(&tasklist_lock); retval = -ESRCH; @@ -140,7 +140,7 @@ asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len, out_unlock: read_unlock(&tasklist_lock); - unlock_cpu_hotplug(); + put_online_cpus(); if (retval) return retval; if (copy_to_user(user_mask_ptr, &mask, real_len)) diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c index 412e6b4298..c4ad54e0f2 100644 --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c @@ -153,7 +153,7 @@ static int pseries_add_processor(struct device_node *np) for (i = 0; i < nthreads; i++) cpu_set(i, tmp); - lock_cpu_hotplug(); + cpu_maps_update_begin(); BUG_ON(!cpus_subset(cpu_present_map, cpu_possible_map)); @@ -190,7 +190,7 @@ static int pseries_add_processor(struct device_node *np) } err = 0; out_unlock: - unlock_cpu_hotplug(); + cpu_maps_update_done(); return err; } @@ -211,7 +211,7 @@ static void pseries_remove_processor(struct device_node *np) nthreads = len / sizeof(u32); - lock_cpu_hotplug(); + cpu_maps_update_begin(); for (i = 0; i < nthreads; i++) { for_each_present_cpu(cpu) { if (get_hard_smp_processor_id(cpu) != intserv[i]) @@ -225,7 +225,7 @@ static void pseries_remove_processor(struct device_node *np) printk(KERN_WARNING "Could not find cpu to remove " "with physical id 0x%x\n", intserv[i]); } - unlock_cpu_hotplug(); + cpu_maps_update_done(); } static int pseries_smp_notifier(struct notifier_block *nb, diff --git a/arch/powerpc/platforms/pseries/rtasd.c b/arch/powerpc/platforms/pseries/rtasd.c index 73401c8201..e3078ce415 100644 --- a/arch/powerpc/platforms/pseries/rtasd.c +++ b/arch/powerpc/platforms/pseries/rtasd.c @@ -382,7 +382,7 @@ static void do_event_scan_all_cpus(long delay) { int cpu; - lock_cpu_hotplug(); + get_online_cpus(); cpu = first_cpu(cpu_online_map); for (;;) { set_cpus_allowed(current, cpumask_of_cpu(cpu)); @@ -390,15 +390,15 @@ static void do_event_scan_all_cpus(long delay) set_cpus_allowed(current, CPU_MASK_ALL); /* Drop hotplug lock, and sleep for the specified delay */ - unlock_cpu_hotplug(); + put_online_cpus(); msleep_interruptible(delay); - lock_cpu_hotplug(); + get_online_cpus(); cpu = next_cpu(cpu, cpu_online_map); if (cpu == NR_CPUS) break; } - unlock_cpu_hotplug(); + put_online_cpus(); } static int rtasd(void *unused) diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c index 3b20613325..beb45c9c08 100644 --- a/arch/x86/kernel/cpu/mtrr/main.c +++ b/arch/x86/kernel/cpu/mtrr/main.c @@ -349,7 +349,7 @@ int mtrr_add_page(unsigned long base, unsigned long size, replace = -1; /* No CPU hotplug when we change MTRR entries */ - lock_cpu_hotplug(); + get_online_cpus(); /* Search for existing MTRR */ mutex_lock(&mtrr_mutex); for (i = 0; i < num_var_ranges; ++i) { @@ -405,7 +405,7 @@ int mtrr_add_page(unsigned long base, unsigned long size, error = i; out: mutex_unlock(&mtrr_mutex); - unlock_cpu_hotplug(); + put_online_cpus(); return error; } @@ -495,7 +495,7 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size) max = num_var_ranges; /* No CPU hotplug when we change MTRR entries */ - lock_cpu_hotplug(); + get_online_cpus(); mutex_lock(&mtrr_mutex); if (reg < 0) { /* Search for existing MTRR */ @@ -536,7 +536,7 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size) error = reg; out: mutex_unlock(&mtrr_mutex); - unlock_cpu_hotplug(); + put_online_cpus(); return error; } /** diff --git a/arch/x86/kernel/microcode.c b/arch/x86/kernel/microcode.c index 09c315214a..40cfd54887 100644 --- a/arch/x86/kernel/microcode.c +++ b/arch/x86/kernel/microcode.c @@ -436,7 +436,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_ return -EINVAL; } - lock_cpu_hotplug(); + get_online_cpus(); mutex_lock(µcode_mutex); user_buffer = (void __user *) buf; @@ -447,7 +447,7 @@ static ssize_t microcode_write (struct file *file, const char __user *buf, size_ ret = (ssize_t)len; mutex_unlock(µcode_mutex); - unlock_cpu_hotplug(); + put_online_cpus(); return ret; } @@ -658,14 +658,14 @@ static ssize_t reload_store(struct sys_device *dev, const char *buf, size_t sz) old = current->cpus_allowed; - lock_cpu_hotplug(); + get_online_cpus(); set_cpus_allowed(current, cpumask_of_cpu(cpu)); mutex_lock(µcode_mutex); if (uci->valid) err = cpu_request_microcode(cpu); mutex_unlock(µcode_mutex); - unlock_cpu_hotplug(); + put_online_cpus(); set_cpus_allowed(current, old); } if (err) @@ -817,9 +817,9 @@ static int __init microcode_init (void) return PTR_ERR(microcode_pdev); } - lock_cpu_hotplug(); + get_online_cpus(); error = sysdev_driver_register(&cpu_sysdev_class, &mc_sysdev_driver); - unlock_cpu_hotplug(); + put_online_cpus(); if (error) { microcode_dev_exit(); platform_device_unregister(microcode_pdev); @@ -839,9 +839,9 @@ static void __exit microcode_exit (void) unregister_hotcpu_notifier(&mc_cpu_notifier); - lock_cpu_hotplug(); + get_online_cpus(); sysdev_driver_unregister(&cpu_sysdev_class, &mc_sysdev_driver); - unlock_cpu_hotplug(); + put_online_cpus(); platform_device_unregister(microcode_pdev); } diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c index 482aec2a96..96d0fd07c5 100644 --- a/drivers/lguest/x86/core.c +++ b/drivers/lguest/x86/core.c @@ -459,7 +459,7 @@ void __init lguest_arch_host_init(void) /* We don't need the complexity of CPUs coming and going while we're * doing this. */ - lock_cpu_hotplug(); + get_online_cpus(); if (cpu_has_pge) { /* We have a broader idea of "global". */ /* Remember that this was originally set (for cleanup). */ cpu_had_pge = 1; @@ -469,20 +469,20 @@ void __init lguest_arch_host_init(void) /* Turn off the feature in the global feature set. */ clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); } - unlock_cpu_hotplug(); + put_online_cpus(); }; /*:*/ void __exit lguest_arch_host_fini(void) { /* If we had PGE before we started, turn it back on now. */ - lock_cpu_hotplug(); + get_online_cpus(); if (cpu_had_pge) { set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); /* adjust_pge's argument "1" means set PGE. */ on_each_cpu(adjust_pge, (void *)1, 0, 1); } - unlock_cpu_hotplug(); + put_online_cpus(); } diff --git a/drivers/s390/char/sclp_config.c b/drivers/s390/char/sclp_config.c index 5322e5e54a..9dc77f14fa 100644 --- a/drivers/s390/char/sclp_config.c +++ b/drivers/s390/char/sclp_config.c @@ -29,12 +29,12 @@ static void sclp_cpu_capability_notify(struct work_struct *work) struct sys_device *sysdev; printk(KERN_WARNING TAG "cpu capability changed.\n"); - lock_cpu_hotplug(); + get_online_cpus(); for_each_online_cpu(cpu) { sysdev = get_cpu_sysdev(cpu); kobject_uevent(&sysdev->kobj, KOBJ_CHANGE); } - unlock_cpu_hotplug(); + put_online_cpus(); } static void sclp_conf_receiver_fn(struct evbuf_header *evbuf) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index a40247e4d4..3a3ff1c5cb 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -100,8 +100,8 @@ static inline void cpuhotplug_mutex_unlock(struct mutex *cpu_hp_mutex) mutex_unlock(cpu_hp_mutex); } -extern void lock_cpu_hotplug(void); -extern void unlock_cpu_hotplug(void); +extern void get_online_cpus(void); +extern void put_online_cpus(void); #define hotcpu_notifier(fn, pri) { \ static struct notifier_block fn##_nb = \ { .notifier_call = fn, .priority = pri }; \ @@ -118,8 +118,8 @@ static inline void cpuhotplug_mutex_lock(struct mutex *cpu_hp_mutex) static inline void cpuhotplug_mutex_unlock(struct mutex *cpu_hp_mutex) { } -#define lock_cpu_hotplug() do { } while (0) -#define unlock_cpu_hotplug() do { } while (0) +#define get_online_cpus() do { } while (0) +#define put_online_cpus() do { } while (0) #define hotcpu_notifier(fn, pri) do { (void)(fn); } while (0) /* These aren't inline functions due to a GCC bug. */ #define register_hotcpu_notifier(nb) ({ (void)(nb); 0; }) diff --git a/kernel/cpu.c b/kernel/cpu.c index 656dc3fcbb..b0c4152995 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -48,7 +48,7 @@ void __init cpu_hotplug_init(void) #ifdef CONFIG_HOTPLUG_CPU -void lock_cpu_hotplug(void) +void get_online_cpus(void) { might_sleep(); if (cpu_hotplug.active_writer == current) @@ -58,9 +58,9 @@ void lock_cpu_hotplug(void) mutex_unlock(&cpu_hotplug.lock); } -EXPORT_SYMBOL_GPL(lock_cpu_hotplug); +EXPORT_SYMBOL_GPL(get_online_cpus); -void unlock_cpu_hotplug(void) +void put_online_cpus(void) { if (cpu_hotplug.active_writer == current) return; @@ -73,7 +73,7 @@ void unlock_cpu_hotplug(void) mutex_unlock(&cpu_hotplug.lock); } -EXPORT_SYMBOL_GPL(unlock_cpu_hotplug); +EXPORT_SYMBOL_GPL(put_online_cpus); #endif /* CONFIG_HOTPLUG_CPU */ @@ -110,7 +110,7 @@ void cpu_maps_update_done(void) * non zero and goes to sleep again. * * However, this is very difficult to achieve in practice since - * lock_cpu_hotplug() not an api which is called all that often. + * get_online_cpus() not an api which is called all that often. * */ static void cpu_hotplug_begin(void) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 50f5dc4636..cfaf6419d8 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -537,10 +537,10 @@ static int cpusets_overlap(struct cpuset *a, struct cpuset *b) * * Call with cgroup_mutex held. May take callback_mutex during * call due to the kfifo_alloc() and kmalloc() calls. May nest - * a call to the lock_cpu_hotplug()/unlock_cpu_hotplug() pair. + * a call to the get_online_cpus()/put_online_cpus() pair. * Must not be called holding callback_mutex, because we must not - * call lock_cpu_hotplug() while holding callback_mutex. Elsewhere - * the kernel nests callback_mutex inside lock_cpu_hotplug() calls. + * call get_online_cpus() while holding callback_mutex. Elsewhere + * the kernel nests callback_mutex inside get_online_cpus() calls. * So the reverse nesting would risk an ABBA deadlock. * * The three key local variables below are: @@ -691,9 +691,9 @@ restart: rebuild: /* Have scheduler rebuild sched domains */ - lock_cpu_hotplug(); + get_online_cpus(); partition_sched_domains(ndoms, doms); - unlock_cpu_hotplug(); + put_online_cpus(); done: if (q && !IS_ERR(q)) @@ -1617,10 +1617,10 @@ static struct cgroup_subsys_state *cpuset_create( * * If the cpuset being removed has its flag 'sched_load_balance' * enabled, then simulate turning sched_load_balance off, which - * will call rebuild_sched_domains(). The lock_cpu_hotplug() + * will call rebuild_sched_domains(). The get_online_cpus() * call in rebuild_sched_domains() must not be made while holding * callback_mutex. Elsewhere the kernel nests callback_mutex inside - * lock_cpu_hotplug() calls. So the reverse nesting would risk an + * get_online_cpus() calls. So the reverse nesting would risk an * ABBA deadlock. */ diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index c3e165c231..fd599829e7 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -726,11 +726,11 @@ static void rcu_torture_shuffle_tasks(void) cpumask_t tmp_mask = CPU_MASK_ALL; int i; - lock_cpu_hotplug(); + get_online_cpus(); /* No point in shuffling if there is only one online CPU (ex: UP) */ if (num_online_cpus() == 1) { - unlock_cpu_hotplug(); + put_online_cpus(); return; } @@ -762,7 +762,7 @@ static void rcu_torture_shuffle_tasks(void) else rcu_idle_cpu--; - unlock_cpu_hotplug(); + put_online_cpus(); } /* Shuffle tasks across CPUs, with the intent of allowing each CPU in the diff --git a/kernel/sched.c b/kernel/sched.c index 86e55a9c2d..672aa68bfe 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -7152,7 +7152,7 @@ static int load_balance_monitor(void *unused) int i, cpu, balanced = 1; /* Prevent cpus going down or coming up */ - lock_cpu_hotplug(); + get_online_cpus(); /* lockout changes to doms_cur[] array */ lock_doms_cur(); /* @@ -7186,7 +7186,7 @@ static int load_balance_monitor(void *unused) rcu_read_unlock(); unlock_doms_cur(); - unlock_cpu_hotplug(); + put_online_cpus(); if (!balanced) timeout = sysctl_sched_min_bal_int_shares; diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 319821ef78..51b5ee5357 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -203,13 +203,13 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu) int ret; /* No CPUs can come up or down during this. */ - lock_cpu_hotplug(); + get_online_cpus(); p = __stop_machine_run(fn, data, cpu); if (!IS_ERR(p)) ret = kthread_stop(p); else ret = PTR_ERR(p); - unlock_cpu_hotplug(); + put_online_cpus(); return ret; } diff --git a/net/core/flow.c b/net/core/flow.c index 3ed2b4b1d6..6489f4e24e 100644 --- a/net/core/flow.c +++ b/net/core/flow.c @@ -293,7 +293,7 @@ void flow_cache_flush(void) static DEFINE_MUTEX(flow_flush_sem); /* Don't want cpus going down or up during this. */ - lock_cpu_hotplug(); + get_online_cpus(); mutex_lock(&flow_flush_sem); atomic_set(&info.cpuleft, num_online_cpus()); init_completion(&info.completion); @@ -305,7 +305,7 @@ void flow_cache_flush(void) wait_for_completion(&info.completion); mutex_unlock(&flow_flush_sem); - unlock_cpu_hotplug(); + put_online_cpus(); } static void __devinit flow_cache_cpu_prepare(int cpu) -- 2.39.5