Quelle smp.c Sprache: C

// 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 <linux/string_choices.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.
*
* This runs with interrupts disabled inside the stopper task invoked by
* stop_machine(), ensuring mutually exclusive CPU offlining and IPI flush.
*/
__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, call_single_data_t *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, 0644);
static int panic_on_ipistall;  /* CSD panic timeout in milliseconds, 300000 for five minutes. */
module_param(panic_on_ipistall, int, 0644);

static atomic_t csd_bug_count = ATOMIC_INIT(0);

/* Record current CSD work for current CPU, NULL to erase. */
static void __csd_lock_record(call_single_data_t *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(call_single_data_t *csd)
{
if (static_branch_unlikely(&csdlock_debug_enabled))
  __csd_lock_record(csd);
}

static int csd_lock_wait_getcpu(call_single_data_t *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;
}

static atomic_t n_csd_lock_stuck;

/**
* csd_lock_is_stuck - Has a CSD-lock acquisition been stuck too long?
*
* Returns @true if a CSD-lock acquisition is stuck and has been stuck
* long enough for a "non-responsive CSD lock" message to be printed.
*/
bool csd_lock_is_stuck(void)
{
return !!atomic_read(&n_csd_lock_stuck);
}

/*
* 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(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id, unsigned long *nmessages)
{
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);
  atomic_dec(&n_csd_lock_stuck);
  return true;
}

ts2 = ktime_get_mono_fast_ns();
/* How long since we last checked for a stuck CSD lock.*/
ts_delta = ts2 - *ts1;
if (likely(ts_delta <= csd_lock_timeout_ns * (*nmessages + 1) *
          (!*nmessages ? 1 : (ilog2(num_online_cpus()) / 2 + 1)) ||
     csd_lock_timeout_ns == 0))
  return false;

if (ts0 > ts2) {
  /* Our own sched_clock went backward; don't blame another CPU. */
  ts_delta = ts0 - ts2;
  pr_alert("sched_clock on CPU %d went backward by %llu ns\n", raw_smp_processor_id(), ts_delta);
  *ts1 = ts2;
  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 %lld ns for CPU#%02d %pS(%ps).\n",
   firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), (s64)ts_delta,
   cpu, csd->func, csd->info);
(*nmessages)++;
if (firsttime)
  atomic_inc(&n_csd_lock_stuck);
/*
* 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(call_single_data_t *csd)
{
unsigned long nmessages = 0;
int bug_id = 0;
u64 ts0, ts1;

ts1 = ts0 = ktime_get_mono_fast_ns();
for (;;) {
  if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages))
   break;
  cpu_relax();
}
smp_acquire__after_ctrl_dep();
}

static __always_inline void csd_lock_wait(call_single_data_t *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(call_single_data_t *csd)
{
}

static __always_inline void csd_lock_wait(call_single_data_t *csd)
{
smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK));
}
#endif

static __always_inline void csd_lock(call_single_data_t *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(call_single_data_t *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, call_single_data_t *csd)
{
/*
* Preemption already disabled here so stopper cannot run on this CPU,
* ensuring mutually exclusive CPU offlining and last IPI flush.
*/
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 CPU, as well as CPU
* removal. This prevents stopper from running on this CPU, thus
* providing mutual exclusion of the below cpu_online() check and
* IPI sending ensuring IPI are not missed by CPU going offline.
*/
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, call_single_data_t *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) nearest cpu in @mask, based on NUMA topology
*/
int smp_call_function_any(const struct cpumask *mask,
     smp_call_func_t func, void *info, int wait)
{
unsigned int cpu;
int ret;

/* Try for same CPU (cheapest) */
cpu = get_cpu();
if (!cpumask_test_cpu(cpu, mask))
  cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu));

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;

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 remote execution, i.e., any CPU excluding this one. */
if (cpumask_any_and_but(mask, cpu_online_mask, this_cpu) < nr_cpu_ids) {
  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;
   }

   /* Work is enqueued on a remote CPU. */
   run_remote = true;

   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);

   /*
* Kick the remote CPU if this is the first work
* item enqueued.
*/
   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);
}

/* Check if we need local execution. */
if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) &&
     (!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: If true, wait (atomically) until function has completed
*        on other CPUs.
*
* 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.
*
* @func is not called on the local CPU even if @mask contains it.  Consider
* using on_each_cpu_cond_mask() instead if this is not desirable.
*/
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, str_plural(num_nodes), num_cpus, str_plural(num_cpus));

/* 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 boolean 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);
destroy_work_on_stack(&sscs.work);

return sscs.ret;
}
EXPORT_SYMBOL_GPL(smp_call_on_cpu);

quality99%

¤ Dauer der Verarbeitung: 0.48 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.