diff options
Diffstat (limited to 'kernel/smp.c')
| -rw-r--r-- | kernel/smp.c | 1125 |
1 files changed, 1125 insertions, 0 deletions
diff --git a/kernel/smp.c b/kernel/smp.c new file mode 100644 index 0000000000..695eb13a27 --- /dev/null +++ b/kernel/smp.c @@ -0,0 +1,1125 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Generic helpers for smp ipi calls + * + * (C) Jens Axboe <jens.axboe@oracle.com> 2008 + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/irq_work.h> +#include <linux/rcupdate.h> +#include <linux/rculist.h> +#include <linux/kernel.h> +#include <linux/export.h> +#include <linux/percpu.h> +#include <linux/init.h> +#include <linux/interrupt.h> +#include <linux/gfp.h> +#include <linux/smp.h> +#include <linux/cpu.h> +#include <linux/sched.h> +#include <linux/sched/idle.h> +#include <linux/hypervisor.h> +#include <linux/sched/clock.h> +#include <linux/nmi.h> +#include <linux/sched/debug.h> +#include <linux/jump_label.h> + +#include <trace/events/ipi.h> +#define CREATE_TRACE_POINTS +#include <trace/events/csd.h> +#undef CREATE_TRACE_POINTS + +#include "smpboot.h" +#include "sched/smp.h" + +#define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK) + +struct call_function_data { + call_single_data_t __percpu *csd; + cpumask_var_t cpumask; + cpumask_var_t cpumask_ipi; +}; + +static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data); + +static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue); + +static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1); + +static void __flush_smp_call_function_queue(bool warn_cpu_offline); + +int smpcfd_prepare_cpu(unsigned int cpu) +{ + struct call_function_data *cfd = &per_cpu(cfd_data, cpu); + + if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, + cpu_to_node(cpu))) + return -ENOMEM; + if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, + cpu_to_node(cpu))) { + free_cpumask_var(cfd->cpumask); + return -ENOMEM; + } + cfd->csd = alloc_percpu(call_single_data_t); + if (!cfd->csd) { + free_cpumask_var(cfd->cpumask); + free_cpumask_var(cfd->cpumask_ipi); + return -ENOMEM; + } + + return 0; +} + +int smpcfd_dead_cpu(unsigned int cpu) +{ + struct call_function_data *cfd = &per_cpu(cfd_data, cpu); + + free_cpumask_var(cfd->cpumask); + free_cpumask_var(cfd->cpumask_ipi); + free_percpu(cfd->csd); + return 0; +} + +int smpcfd_dying_cpu(unsigned int cpu) +{ + /* + * The IPIs for the smp-call-function callbacks queued by other + * CPUs might arrive late, either due to hardware latencies or + * because this CPU disabled interrupts (inside stop-machine) + * before the IPIs were sent. So flush out any pending callbacks + * explicitly (without waiting for the IPIs to arrive), to + * ensure that the outgoing CPU doesn't go offline with work + * still pending. + */ + __flush_smp_call_function_queue(false); + irq_work_run(); + return 0; +} + +void __init call_function_init(void) +{ + int i; + + for_each_possible_cpu(i) + init_llist_head(&per_cpu(call_single_queue, i)); + + smpcfd_prepare_cpu(smp_processor_id()); +} + +static __always_inline void +send_call_function_single_ipi(int cpu) +{ + if (call_function_single_prep_ipi(cpu)) { + trace_ipi_send_cpu(cpu, _RET_IP_, + generic_smp_call_function_single_interrupt); + arch_send_call_function_single_ipi(cpu); + } +} + +static __always_inline void +send_call_function_ipi_mask(struct cpumask *mask) +{ + trace_ipi_send_cpumask(mask, _RET_IP_, + generic_smp_call_function_single_interrupt); + arch_send_call_function_ipi_mask(mask); +} + +static __always_inline void +csd_do_func(smp_call_func_t func, void *info, struct __call_single_data *csd) +{ + trace_csd_function_entry(func, csd); + func(info); + trace_csd_function_exit(func, csd); +} + +#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG + +static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled); + +/* + * Parse the csdlock_debug= kernel boot parameter. + * + * If you need to restore the old "ext" value that once provided + * additional debugging information, reapply the following commits: + * + * de7b09ef658d ("locking/csd_lock: Prepare more CSD lock debugging") + * a5aabace5fb8 ("locking/csd_lock: Add more data to CSD lock debugging") + */ +static int __init csdlock_debug(char *str) +{ + int ret; + unsigned int val = 0; + + ret = get_option(&str, &val); + if (ret) { + if (val) + static_branch_enable(&csdlock_debug_enabled); + else + static_branch_disable(&csdlock_debug_enabled); + } + + return 1; +} +__setup("csdlock_debug=", csdlock_debug); + +static DEFINE_PER_CPU(call_single_data_t *, cur_csd); +static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func); +static DEFINE_PER_CPU(void *, cur_csd_info); + +static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */ +module_param(csd_lock_timeout, ulong, 0444); +static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */ +module_param(panic_on_ipistall, int, 0444); + +static atomic_t csd_bug_count = ATOMIC_INIT(0); + +/* Record current CSD work for current CPU, NULL to erase. */ +static void __csd_lock_record(struct __call_single_data *csd) +{ + if (!csd) { + smp_mb(); /* NULL cur_csd after unlock. */ + __this_cpu_write(cur_csd, NULL); + return; + } + __this_cpu_write(cur_csd_func, csd->func); + __this_cpu_write(cur_csd_info, csd->info); + smp_wmb(); /* func and info before csd. */ + __this_cpu_write(cur_csd, csd); + smp_mb(); /* Update cur_csd before function call. */ + /* Or before unlock, as the case may be. */ +} + +static __always_inline void csd_lock_record(struct __call_single_data *csd) +{ + if (static_branch_unlikely(&csdlock_debug_enabled)) + __csd_lock_record(csd); +} + +static int csd_lock_wait_getcpu(struct __call_single_data *csd) +{ + unsigned int csd_type; + + csd_type = CSD_TYPE(csd); + if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC) + return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */ + return -1; +} + +/* + * Complain if too much time spent waiting. Note that only + * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU, + * so waiting on other types gets much less information. + */ +static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 *ts1, int *bug_id) +{ + int cpu = -1; + int cpux; + bool firsttime; + u64 ts2, ts_delta; + call_single_data_t *cpu_cur_csd; + unsigned int flags = READ_ONCE(csd->node.u_flags); + unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC; + + if (!(flags & CSD_FLAG_LOCK)) { + if (!unlikely(*bug_id)) + return true; + cpu = csd_lock_wait_getcpu(csd); + pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n", + *bug_id, raw_smp_processor_id(), cpu); + return true; + } + + ts2 = sched_clock(); + /* How long since we last checked for a stuck CSD lock.*/ + ts_delta = ts2 - *ts1; + if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0)) + return false; + + firsttime = !*bug_id; + if (firsttime) + *bug_id = atomic_inc_return(&csd_bug_count); + cpu = csd_lock_wait_getcpu(csd); + if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu)) + cpux = 0; + else + cpux = cpu; + cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */ + /* How long since this CSD lock was stuck. */ + ts_delta = ts2 - ts0; + pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n", + firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts_delta, + cpu, csd->func, csd->info); + /* + * If the CSD lock is still stuck after 5 minutes, it is unlikely + * to become unstuck. Use a signed comparison to avoid triggering + * on underflows when the TSC is out of sync between sockets. + */ + BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC)); + if (cpu_cur_csd && csd != cpu_cur_csd) { + pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n", + *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)), + READ_ONCE(per_cpu(cur_csd_info, cpux))); + } else { + pr_alert("\tcsd: CSD lock (#%d) %s.\n", + *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request"); + } + if (cpu >= 0) { + if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0)) + dump_cpu_task(cpu); + if (!cpu_cur_csd) { + pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu); + arch_send_call_function_single_ipi(cpu); + } + } + if (firsttime) + dump_stack(); + *ts1 = ts2; + + return false; +} + +/* + * csd_lock/csd_unlock used to serialize access to per-cpu csd resources + * + * For non-synchronous ipi calls the csd can still be in use by the + * previous function call. For multi-cpu calls its even more interesting + * as we'll have to ensure no other cpu is observing our csd. + */ +static void __csd_lock_wait(struct __call_single_data *csd) +{ + int bug_id = 0; + u64 ts0, ts1; + + ts1 = ts0 = sched_clock(); + for (;;) { + if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id)) + break; + cpu_relax(); + } + smp_acquire__after_ctrl_dep(); +} + +static __always_inline void csd_lock_wait(struct __call_single_data *csd) +{ + if (static_branch_unlikely(&csdlock_debug_enabled)) { + __csd_lock_wait(csd); + return; + } + + smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); +} +#else +static void csd_lock_record(struct __call_single_data *csd) +{ +} + +static __always_inline void csd_lock_wait(struct __call_single_data *csd) +{ + smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); +} +#endif + +static __always_inline void csd_lock(struct __call_single_data *csd) +{ + csd_lock_wait(csd); + csd->node.u_flags |= CSD_FLAG_LOCK; + + /* + * prevent CPU from reordering the above assignment + * to ->flags with any subsequent assignments to other + * fields of the specified call_single_data_t structure: + */ + smp_wmb(); +} + +static __always_inline void csd_unlock(struct __call_single_data *csd) +{ + WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK)); + + /* + * ensure we're all done before releasing data: + */ + smp_store_release(&csd->node.u_flags, 0); +} + +static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data); + +void __smp_call_single_queue(int cpu, struct llist_node *node) +{ + /* + * We have to check the type of the CSD before queueing it, because + * once queued it can have its flags cleared by + * flush_smp_call_function_queue() + * even if we haven't sent the smp_call IPI yet (e.g. the stopper + * executes migration_cpu_stop() on the remote CPU). + */ + if (trace_csd_queue_cpu_enabled()) { + call_single_data_t *csd; + smp_call_func_t func; + + csd = container_of(node, call_single_data_t, node.llist); + func = CSD_TYPE(csd) == CSD_TYPE_TTWU ? + sched_ttwu_pending : csd->func; + + trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); + } + + /* + * The list addition should be visible to the target CPU when it pops + * the head of the list to pull the entry off it in the IPI handler + * because of normal cache coherency rules implied by the underlying + * llist ops. + * + * If IPIs can go out of order to the cache coherency protocol + * in an architecture, sufficient synchronisation should be added + * to arch code to make it appear to obey cache coherency WRT + * locking and barrier primitives. Generic code isn't really + * equipped to do the right thing... + */ + if (llist_add(node, &per_cpu(call_single_queue, cpu))) + send_call_function_single_ipi(cpu); +} + +/* + * Insert a previously allocated call_single_data_t element + * for execution on the given CPU. data must already have + * ->func, ->info, and ->flags set. + */ +static int generic_exec_single(int cpu, struct __call_single_data *csd) +{ + if (cpu == smp_processor_id()) { + smp_call_func_t func = csd->func; + void *info = csd->info; + unsigned long flags; + + /* + * We can unlock early even for the synchronous on-stack case, + * since we're doing this from the same CPU.. + */ + csd_lock_record(csd); + csd_unlock(csd); + local_irq_save(flags); + csd_do_func(func, info, NULL); + csd_lock_record(NULL); + local_irq_restore(flags); + return 0; + } + + if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) { + csd_unlock(csd); + return -ENXIO; + } + + __smp_call_single_queue(cpu, &csd->node.llist); + + return 0; +} + +/** + * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks + * + * Invoked by arch to handle an IPI for call function single. + * Must be called with interrupts disabled. + */ +void generic_smp_call_function_single_interrupt(void) +{ + __flush_smp_call_function_queue(true); +} + +/** + * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks + * + * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an + * offline CPU. Skip this check if set to 'false'. + * + * Flush any pending smp-call-function callbacks queued on this CPU. This is + * invoked by the generic IPI handler, as well as by a CPU about to go offline, + * to ensure that all pending IPI callbacks are run before it goes completely + * offline. + * + * Loop through the call_single_queue and run all the queued callbacks. + * Must be called with interrupts disabled. + */ +static void __flush_smp_call_function_queue(bool warn_cpu_offline) +{ + call_single_data_t *csd, *csd_next; + struct llist_node *entry, *prev; + struct llist_head *head; + static bool warned; + atomic_t *tbt; + + lockdep_assert_irqs_disabled(); + + /* Allow waiters to send backtrace NMI from here onwards */ + tbt = this_cpu_ptr(&trigger_backtrace); + atomic_set_release(tbt, 1); + + head = this_cpu_ptr(&call_single_queue); + entry = llist_del_all(head); + entry = llist_reverse_order(entry); + + /* There shouldn't be any pending callbacks on an offline CPU. */ + if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && + !warned && entry != NULL)) { + warned = true; + WARN(1, "IPI on offline CPU %d\n", smp_processor_id()); + + /* + * We don't have to use the _safe() variant here + * because we are not invoking the IPI handlers yet. + */ + llist_for_each_entry(csd, entry, node.llist) { + switch (CSD_TYPE(csd)) { + case CSD_TYPE_ASYNC: + case CSD_TYPE_SYNC: + case CSD_TYPE_IRQ_WORK: + pr_warn("IPI callback %pS sent to offline CPU\n", + csd->func); + break; + + case CSD_TYPE_TTWU: + pr_warn("IPI task-wakeup sent to offline CPU\n"); + break; + + default: + pr_warn("IPI callback, unknown type %d, sent to offline CPU\n", + CSD_TYPE(csd)); + break; + } + } + } + + /* + * First; run all SYNC callbacks, people are waiting for us. + */ + prev = NULL; + llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { + /* Do we wait until *after* callback? */ + if (CSD_TYPE(csd) == CSD_TYPE_SYNC) { + smp_call_func_t func = csd->func; + void *info = csd->info; + + if (prev) { + prev->next = &csd_next->node.llist; + } else { + entry = &csd_next->node.llist; + } + + csd_lock_record(csd); + csd_do_func(func, info, csd); + csd_unlock(csd); + csd_lock_record(NULL); + } else { + prev = &csd->node.llist; + } + } + + if (!entry) + return; + + /* + * Second; run all !SYNC callbacks. + */ + prev = NULL; + llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { + int type = CSD_TYPE(csd); + + if (type != CSD_TYPE_TTWU) { + if (prev) { + prev->next = &csd_next->node.llist; + } else { + entry = &csd_next->node.llist; + } + + if (type == CSD_TYPE_ASYNC) { + smp_call_func_t func = csd->func; + void *info = csd->info; + + csd_lock_record(csd); + csd_unlock(csd); + csd_do_func(func, info, csd); + csd_lock_record(NULL); + } else if (type == CSD_TYPE_IRQ_WORK) { + irq_work_single(csd); + } + + } else { + prev = &csd->node.llist; + } + } + + /* + * Third; only CSD_TYPE_TTWU is left, issue those. + */ + if (entry) { + csd = llist_entry(entry, typeof(*csd), node.llist); + csd_do_func(sched_ttwu_pending, entry, csd); + } +} + + +/** + * flush_smp_call_function_queue - Flush pending smp-call-function callbacks + * from task context (idle, migration thread) + * + * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it + * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by + * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to + * handle queued SMP function calls before scheduling. + * + * The migration thread has to ensure that an eventually pending wakeup has + * been handled before it migrates a task. + */ +void flush_smp_call_function_queue(void) +{ + unsigned int was_pending; + unsigned long flags; + + if (llist_empty(this_cpu_ptr(&call_single_queue))) + return; + + local_irq_save(flags); + /* Get the already pending soft interrupts for RT enabled kernels */ + was_pending = local_softirq_pending(); + __flush_smp_call_function_queue(true); + if (local_softirq_pending()) + do_softirq_post_smp_call_flush(was_pending); + + local_irq_restore(flags); +} + +/* + * smp_call_function_single - Run a function on a specific CPU + * @func: The function to run. This must be fast and non-blocking. + * @info: An arbitrary pointer to pass to the function. + * @wait: If true, wait until function has completed on other CPUs. + * + * Returns 0 on success, else a negative status code. + */ +int smp_call_function_single(int cpu, smp_call_func_t func, void *info, + int wait) +{ + call_single_data_t *csd; + call_single_data_t csd_stack = { + .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, }, + }; + int this_cpu; + int err; + + /* + * prevent preemption and reschedule on another processor, + * as well as CPU removal + */ + this_cpu = get_cpu(); + + /* + * Can deadlock when called with interrupts disabled. + * We allow cpu's that are not yet online though, as no one else can + * send smp call function interrupt to this cpu and as such deadlocks + * can't happen. + */ + WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() + && !oops_in_progress); + + /* + * When @wait we can deadlock when we interrupt between llist_add() and + * arch_send_call_function_ipi*(); when !@wait we can deadlock due to + * csd_lock() on because the interrupt context uses the same csd + * storage. + */ + WARN_ON_ONCE(!in_task()); + + csd = &csd_stack; + if (!wait) { + csd = this_cpu_ptr(&csd_data); + csd_lock(csd); + } + + csd->func = func; + csd->info = info; +#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG + csd->node.src = smp_processor_id(); + csd->node.dst = cpu; +#endif + + err = generic_exec_single(cpu, csd); + + if (wait) + csd_lock_wait(csd); + + put_cpu(); + + return err; +} +EXPORT_SYMBOL(smp_call_function_single); + +/** + * smp_call_function_single_async() - Run an asynchronous function on a + * specific CPU. + * @cpu: The CPU to run on. + * @csd: Pre-allocated and setup data structure + * + * Like smp_call_function_single(), but the call is asynchonous and + * can thus be done from contexts with disabled interrupts. + * + * The caller passes his own pre-allocated data structure + * (ie: embedded in an object) and is responsible for synchronizing it + * such that the IPIs performed on the @csd are strictly serialized. + * + * If the function is called with one csd which has not yet been + * processed by previous call to smp_call_function_single_async(), the + * function will return immediately with -EBUSY showing that the csd + * object is still in progress. + * + * NOTE: Be careful, there is unfortunately no current debugging facility to + * validate the correctness of this serialization. + * + * Return: %0 on success or negative errno value on error + */ +int smp_call_function_single_async(int cpu, struct __call_single_data *csd) +{ + int err = 0; + + preempt_disable(); + + if (csd->node.u_flags & CSD_FLAG_LOCK) { + err = -EBUSY; + goto out; + } + + csd->node.u_flags = CSD_FLAG_LOCK; + smp_wmb(); + + err = generic_exec_single(cpu, csd); + +out: + preempt_enable(); + + return err; +} +EXPORT_SYMBOL_GPL(smp_call_function_single_async); + +/* + * smp_call_function_any - Run a function on any of the given cpus + * @mask: The mask of cpus it can run on. + * @func: The function to run. This must be fast and non-blocking. + * @info: An arbitrary pointer to pass to the function. + * @wait: If true, wait until function has completed. + * + * Returns 0 on success, else a negative status code (if no cpus were online). + * + * Selection preference: + * 1) current cpu if in @mask + * 2) any cpu of current node if in @mask + * 3) any other online cpu in @mask + */ +int smp_call_function_any(const struct cpumask *mask, + smp_call_func_t func, void *info, int wait) +{ + unsigned int cpu; + const struct cpumask *nodemask; + int ret; + + /* Try for same CPU (cheapest) */ + cpu = get_cpu(); + if (cpumask_test_cpu(cpu, mask)) + goto call; + + /* Try for same node. */ + nodemask = cpumask_of_node(cpu_to_node(cpu)); + for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; + cpu = cpumask_next_and(cpu, nodemask, mask)) { + if (cpu_online(cpu)) + goto call; + } + + /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ + cpu = cpumask_any_and(mask, cpu_online_mask); +call: + ret = smp_call_function_single(cpu, func, info, wait); + put_cpu(); + return ret; +} +EXPORT_SYMBOL_GPL(smp_call_function_any); + +/* + * Flags to be used as scf_flags argument of smp_call_function_many_cond(). + * + * %SCF_WAIT: Wait until function execution is completed + * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask + */ +#define SCF_WAIT (1U << 0) +#define SCF_RUN_LOCAL (1U << 1) + +static void smp_call_function_many_cond(const struct cpumask *mask, + smp_call_func_t func, void *info, + unsigned int scf_flags, + smp_cond_func_t cond_func) +{ + int cpu, last_cpu, this_cpu = smp_processor_id(); + struct call_function_data *cfd; + bool wait = scf_flags & SCF_WAIT; + int nr_cpus = 0; + bool run_remote = false; + bool run_local = false; + + lockdep_assert_preemption_disabled(); + + /* + * Can deadlock when called with interrupts disabled. + * We allow cpu's that are not yet online though, as no one else can + * send smp call function interrupt to this cpu and as such deadlocks + * can't happen. + */ + if (cpu_online(this_cpu) && !oops_in_progress && + !early_boot_irqs_disabled) + lockdep_assert_irqs_enabled(); + + /* + * When @wait we can deadlock when we interrupt between llist_add() and + * arch_send_call_function_ipi*(); when !@wait we can deadlock due to + * csd_lock() on because the interrupt context uses the same csd + * storage. + */ + WARN_ON_ONCE(!in_task()); + + /* Check if we need local execution. */ + if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask)) + run_local = true; + + /* Check if we need remote execution, i.e., any CPU excluding this one. */ + cpu = cpumask_first_and(mask, cpu_online_mask); + if (cpu == this_cpu) + cpu = cpumask_next_and(cpu, mask, cpu_online_mask); + if (cpu < nr_cpu_ids) + run_remote = true; + + if (run_remote) { + cfd = this_cpu_ptr(&cfd_data); + cpumask_and(cfd->cpumask, mask, cpu_online_mask); + __cpumask_clear_cpu(this_cpu, cfd->cpumask); + + cpumask_clear(cfd->cpumask_ipi); + for_each_cpu(cpu, cfd->cpumask) { + call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu); + + if (cond_func && !cond_func(cpu, info)) { + __cpumask_clear_cpu(cpu, cfd->cpumask); + continue; + } + + csd_lock(csd); + if (wait) + csd->node.u_flags |= CSD_TYPE_SYNC; + csd->func = func; + csd->info = info; +#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG + csd->node.src = smp_processor_id(); + csd->node.dst = cpu; +#endif + trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); + + if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) { + __cpumask_set_cpu(cpu, cfd->cpumask_ipi); + nr_cpus++; + last_cpu = cpu; + } + } + + /* + * Choose the most efficient way to send an IPI. Note that the + * number of CPUs might be zero due to concurrent changes to the + * provided mask. + */ + if (nr_cpus == 1) + send_call_function_single_ipi(last_cpu); + else if (likely(nr_cpus > 1)) + send_call_function_ipi_mask(cfd->cpumask_ipi); + } + + if (run_local && (!cond_func || cond_func(this_cpu, info))) { + unsigned long flags; + + local_irq_save(flags); + csd_do_func(func, info, NULL); + local_irq_restore(flags); + } + + if (run_remote && wait) { + for_each_cpu(cpu, cfd->cpumask) { + call_single_data_t *csd; + + csd = per_cpu_ptr(cfd->csd, cpu); + csd_lock_wait(csd); + } + } +} + +/** + * smp_call_function_many(): Run a function on a set of CPUs. + * @mask: The set of cpus to run on (only runs on online subset). + * @func: The function to run. This must be fast and non-blocking. + * @info: An arbitrary pointer to pass to the function. + * @wait: Bitmask that controls the operation. If %SCF_WAIT is set, wait + * (atomically) until function has completed on other CPUs. If + * %SCF_RUN_LOCAL is set, the function will also be run locally + * if the local CPU is set in the @cpumask. + * + * If @wait is true, then returns once @func has returned. + * + * You must not call this function with disabled interrupts or from a + * hardware interrupt handler or from a bottom half handler. Preemption + * must be disabled when calling this function. + */ +void smp_call_function_many(const struct cpumask *mask, + smp_call_func_t func, void *info, bool wait) +{ + smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL); +} +EXPORT_SYMBOL(smp_call_function_many); + +/** + * smp_call_function(): Run a function on all other CPUs. + * @func: The function to run. This must be fast and non-blocking. + * @info: An arbitrary pointer to pass to the function. + * @wait: If true, wait (atomically) until function has completed + * on other CPUs. + * + * Returns 0. + * + * If @wait is true, then returns once @func has returned; otherwise + * it returns just before the target cpu calls @func. + * + * You must not call this function with disabled interrupts or from a + * hardware interrupt handler or from a bottom half handler. + */ +void smp_call_function(smp_call_func_t func, void *info, int wait) +{ + preempt_disable(); + smp_call_function_many(cpu_online_mask, func, info, wait); + preempt_enable(); +} +EXPORT_SYMBOL(smp_call_function); + +/* Setup configured maximum number of CPUs to activate */ +unsigned int setup_max_cpus = NR_CPUS; +EXPORT_SYMBOL(setup_max_cpus); + + +/* + * Setup routine for controlling SMP activation + * + * Command-line option of "nosmp" or "maxcpus=0" will disable SMP + * activation entirely (the MPS table probe still happens, though). + * + * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer + * greater than 0, limits the maximum number of CPUs activated in + * SMP mode to <NUM>. + */ + +void __weak __init arch_disable_smp_support(void) { } + +static int __init nosmp(char *str) +{ + setup_max_cpus = 0; + arch_disable_smp_support(); + + return 0; +} + +early_param("nosmp", nosmp); + +/* this is hard limit */ +static int __init nrcpus(char *str) +{ + int nr_cpus; + + if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids) + set_nr_cpu_ids(nr_cpus); + + return 0; +} + +early_param("nr_cpus", nrcpus); + +static int __init maxcpus(char *str) +{ + get_option(&str, &setup_max_cpus); + if (setup_max_cpus == 0) + arch_disable_smp_support(); + + return 0; +} + +early_param("maxcpus", maxcpus); + +#if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS) +/* Setup number of possible processor ids */ +unsigned int nr_cpu_ids __read_mostly = NR_CPUS; +EXPORT_SYMBOL(nr_cpu_ids); +#endif + +/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ +void __init setup_nr_cpu_ids(void) +{ + set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1); +} + +/* Called by boot processor to activate the rest. */ +void __init smp_init(void) +{ + int num_nodes, num_cpus; + + idle_threads_init(); + cpuhp_threads_init(); + + pr_info("Bringing up secondary CPUs ...\n"); + + bringup_nonboot_cpus(setup_max_cpus); + + num_nodes = num_online_nodes(); + num_cpus = num_online_cpus(); + pr_info("Brought up %d node%s, %d CPU%s\n", + num_nodes, (num_nodes > 1 ? "s" : ""), + num_cpus, (num_cpus > 1 ? "s" : "")); + + /* Any cleanup work */ + smp_cpus_done(setup_max_cpus); +} + +/* + * on_each_cpu_cond(): Call a function on each processor for which + * the supplied function cond_func returns true, optionally waiting + * for all the required CPUs to finish. This may include the local + * processor. + * @cond_func: A callback function that is passed a cpu id and + * the info parameter. The function is called + * with preemption disabled. The function should + * return a blooean value indicating whether to IPI + * the specified CPU. + * @func: The function to run on all applicable CPUs. + * This must be fast and non-blocking. + * @info: An arbitrary pointer to pass to both functions. + * @wait: If true, wait (atomically) until function has + * completed on other CPUs. + * + * Preemption is disabled to protect against CPUs going offline but not online. + * CPUs going online during the call will not be seen or sent an IPI. + * + * You must not call this function with disabled interrupts or + * from a hardware interrupt handler or from a bottom half handler. + */ +void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func, + void *info, bool wait, const struct cpumask *mask) +{ + unsigned int scf_flags = SCF_RUN_LOCAL; + + if (wait) + scf_flags |= SCF_WAIT; + + preempt_disable(); + smp_call_function_many_cond(mask, func, info, scf_flags, cond_func); + preempt_enable(); +} +EXPORT_SYMBOL(on_each_cpu_cond_mask); + +static void do_nothing(void *unused) +{ +} + +/** + * kick_all_cpus_sync - Force all cpus out of idle + * + * Used to synchronize the update of pm_idle function pointer. It's + * called after the pointer is updated and returns after the dummy + * callback function has been executed on all cpus. The execution of + * the function can only happen on the remote cpus after they have + * left the idle function which had been called via pm_idle function + * pointer. So it's guaranteed that nothing uses the previous pointer + * anymore. + */ +void kick_all_cpus_sync(void) +{ + /* Make sure the change is visible before we kick the cpus */ + smp_mb(); + smp_call_function(do_nothing, NULL, 1); +} +EXPORT_SYMBOL_GPL(kick_all_cpus_sync); + +/** + * wake_up_all_idle_cpus - break all cpus out of idle + * wake_up_all_idle_cpus try to break all cpus which is in idle state even + * including idle polling cpus, for non-idle cpus, we will do nothing + * for them. + */ +void wake_up_all_idle_cpus(void) +{ + int cpu; + + for_each_possible_cpu(cpu) { + preempt_disable(); + if (cpu != smp_processor_id() && cpu_online(cpu)) + wake_up_if_idle(cpu); + preempt_enable(); + } +} +EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus); + +/** + * struct smp_call_on_cpu_struct - Call a function on a specific CPU + * @work: &work_struct + * @done: &completion to signal + * @func: function to call + * @data: function's data argument + * @ret: return value from @func + * @cpu: target CPU (%-1 for any CPU) + * + * Used to call a function on a specific cpu and wait for it to return. + * Optionally make sure the call is done on a specified physical cpu via vcpu + * pinning in order to support virtualized environments. + */ +struct smp_call_on_cpu_struct { + struct work_struct work; + struct completion done; + int (*func)(void *); + void *data; + int ret; + int cpu; +}; + +static void smp_call_on_cpu_callback(struct work_struct *work) +{ + struct smp_call_on_cpu_struct *sscs; + + sscs = container_of(work, struct smp_call_on_cpu_struct, work); + if (sscs->cpu >= 0) + hypervisor_pin_vcpu(sscs->cpu); + sscs->ret = sscs->func(sscs->data); + if (sscs->cpu >= 0) + hypervisor_pin_vcpu(-1); + + complete(&sscs->done); +} + +int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys) +{ + struct smp_call_on_cpu_struct sscs = { + .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done), + .func = func, + .data = par, + .cpu = phys ? cpu : -1, + }; + + INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback); + + if (cpu >= nr_cpu_ids || !cpu_online(cpu)) + return -ENXIO; + + queue_work_on(cpu, system_wq, &sscs.work); + wait_for_completion(&sscs.done); + + return sscs.ret; +} +EXPORT_SYMBOL_GPL(smp_call_on_cpu); |