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smp.c
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smp.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
* Generic helpers for smp ipi calls
*
* (C) Jens Axboe <[email protected]> 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 "smpboot.h"
#include "sched/smp.h"
#define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK)
#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
union cfd_seq_cnt {
u64 val;
struct {
u64 src:16;
u64 dst:16;
#define CFD_SEQ_NOCPU 0xffff
u64 type:4;
#define CFD_SEQ_QUEUE 0
#define CFD_SEQ_IPI 1
#define CFD_SEQ_NOIPI 2
#define CFD_SEQ_PING 3
#define CFD_SEQ_PINGED 4
#define CFD_SEQ_HANDLE 5
#define CFD_SEQ_DEQUEUE 6
#define CFD_SEQ_IDLE 7
#define CFD_SEQ_GOTIPI 8
#define CFD_SEQ_HDLEND 9
u64 cnt:28;
} u;
};
static char *seq_type[] = {
[CFD_SEQ_QUEUE] = "queue",
[CFD_SEQ_IPI] = "ipi",
[CFD_SEQ_NOIPI] = "noipi",
[CFD_SEQ_PING] = "ping",
[CFD_SEQ_PINGED] = "pinged",
[CFD_SEQ_HANDLE] = "handle",
[CFD_SEQ_DEQUEUE] = "dequeue (src CPU 0 == empty)",
[CFD_SEQ_IDLE] = "idle",
[CFD_SEQ_GOTIPI] = "gotipi",
[CFD_SEQ_HDLEND] = "hdlend (src CPU 0 == early)",
};
struct cfd_seq_local {
u64 ping;
u64 pinged;
u64 handle;
u64 dequeue;
u64 idle;
u64 gotipi;
u64 hdlend;
};
#endif
struct cfd_percpu {
call_single_data_t csd;
#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
u64 seq_queue;
u64 seq_ipi;
u64 seq_noipi;
#endif
};
struct call_function_data {
struct cfd_percpu __percpu *pcpu;
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 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->pcpu = alloc_percpu(struct cfd_percpu);
if (!cfd->pcpu) {
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->pcpu);
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());
}
#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
static DEFINE_STATIC_KEY_FALSE(csdlock_debug_enabled);
static DEFINE_STATIC_KEY_FALSE(csdlock_debug_extended);
static int __init csdlock_debug(char *str)
{
unsigned int val = 0;
if (str && !strcmp(str, "ext")) {
val = 1;
static_branch_enable(&csdlock_debug_extended);
} else
get_option(&str, &val);
if (val)
static_branch_enable(&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 DEFINE_PER_CPU(struct cfd_seq_local, cfd_seq_local);
static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */
module_param(csd_lock_timeout, ulong, 0444);
static atomic_t csd_bug_count = ATOMIC_INIT(0);
static u64 cfd_seq;
#define CFD_SEQ(s, d, t, c) \
(union cfd_seq_cnt){ .u.src = s, .u.dst = d, .u.type = t, .u.cnt = c }
static u64 cfd_seq_inc(unsigned int src, unsigned int dst, unsigned int type)
{
union cfd_seq_cnt new, old;
new = CFD_SEQ(src, dst, type, 0);
do {
old.val = READ_ONCE(cfd_seq);
new.u.cnt = old.u.cnt + 1;
} while (cmpxchg(&cfd_seq, old.val, new.val) != old.val);
return old.val;
}
#define cfd_seq_store(var, src, dst, type) \
do { \
if (static_branch_unlikely(&csdlock_debug_extended)) \
var = cfd_seq_inc(src, dst, type); \
} while (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;
}
static void cfd_seq_data_add(u64 val, unsigned int src, unsigned int dst,
unsigned int type, union cfd_seq_cnt *data,
unsigned int *n_data, unsigned int now)
{
union cfd_seq_cnt new[2];
unsigned int i, j, k;
new[0].val = val;
new[1] = CFD_SEQ(src, dst, type, new[0].u.cnt + 1);
for (i = 0; i < 2; i++) {
if (new[i].u.cnt <= now)
new[i].u.cnt |= 0x80000000U;
for (j = 0; j < *n_data; j++) {
if (new[i].u.cnt == data[j].u.cnt) {
/* Direct read value trumps generated one. */
if (i == 0)
data[j].val = new[i].val;
break;
}
if (new[i].u.cnt < data[j].u.cnt) {
for (k = *n_data; k > j; k--)
data[k].val = data[k - 1].val;
data[j].val = new[i].val;
(*n_data)++;
break;
}
}
if (j == *n_data) {
data[j].val = new[i].val;
(*n_data)++;
}
}
}
static const char *csd_lock_get_type(unsigned int type)
{
return (type >= ARRAY_SIZE(seq_type)) ? "?" : seq_type[type];
}
static void csd_lock_print_extended(struct __call_single_data *csd, int cpu)
{
struct cfd_seq_local *seq = &per_cpu(cfd_seq_local, cpu);
unsigned int srccpu = csd->node.src;
struct call_function_data *cfd = per_cpu_ptr(&cfd_data, srccpu);
struct cfd_percpu *pcpu = per_cpu_ptr(cfd->pcpu, cpu);
unsigned int now;
union cfd_seq_cnt data[2 * ARRAY_SIZE(seq_type)];
unsigned int n_data = 0, i;
data[0].val = READ_ONCE(cfd_seq);
now = data[0].u.cnt;
cfd_seq_data_add(pcpu->seq_queue, srccpu, cpu, CFD_SEQ_QUEUE, data, &n_data, now);
cfd_seq_data_add(pcpu->seq_ipi, srccpu, cpu, CFD_SEQ_IPI, data, &n_data, now);
cfd_seq_data_add(pcpu->seq_noipi, srccpu, cpu, CFD_SEQ_NOIPI, data, &n_data, now);
cfd_seq_data_add(per_cpu(cfd_seq_local.ping, srccpu), srccpu, CFD_SEQ_NOCPU, CFD_SEQ_PING, data, &n_data, now);
cfd_seq_data_add(per_cpu(cfd_seq_local.pinged, srccpu), srccpu, CFD_SEQ_NOCPU, CFD_SEQ_PINGED, data, &n_data, now);
cfd_seq_data_add(seq->idle, CFD_SEQ_NOCPU, cpu, CFD_SEQ_IDLE, data, &n_data, now);
cfd_seq_data_add(seq->gotipi, CFD_SEQ_NOCPU, cpu, CFD_SEQ_GOTIPI, data, &n_data, now);
cfd_seq_data_add(seq->handle, CFD_SEQ_NOCPU, cpu, CFD_SEQ_HANDLE, data, &n_data, now);
cfd_seq_data_add(seq->dequeue, CFD_SEQ_NOCPU, cpu, CFD_SEQ_DEQUEUE, data, &n_data, now);
cfd_seq_data_add(seq->hdlend, CFD_SEQ_NOCPU, cpu, CFD_SEQ_HDLEND, data, &n_data, now);
for (i = 0; i < n_data; i++) {
pr_alert("\tcsd: cnt(%07x): %04x->%04x %s\n",
data[i].u.cnt & ~0x80000000U, data[i].u.src,
data[i].u.dst, csd_lock_get_type(data[i].u.type));
}
pr_alert("\tcsd: cnt now: %07x\n", now);
}
/*
* 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();
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. */
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(), ts2 - ts0,
cpu, csd->func, csd->info);
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 (static_branch_unlikely(&csdlock_debug_extended))
csd_lock_print_extended(csd, cpu);
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);
}
}
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));
}
static void __smp_call_single_queue_debug(int cpu, struct llist_node *node)
{
unsigned int this_cpu = smp_processor_id();
struct cfd_seq_local *seq = this_cpu_ptr(&cfd_seq_local);
struct call_function_data *cfd = this_cpu_ptr(&cfd_data);
struct cfd_percpu *pcpu = per_cpu_ptr(cfd->pcpu, cpu);
cfd_seq_store(pcpu->seq_queue, this_cpu, cpu, CFD_SEQ_QUEUE);
if (llist_add(node, &per_cpu(call_single_queue, cpu))) {
cfd_seq_store(pcpu->seq_ipi, this_cpu, cpu, CFD_SEQ_IPI);
cfd_seq_store(seq->ping, this_cpu, cpu, CFD_SEQ_PING);
send_call_function_single_ipi(cpu);
cfd_seq_store(seq->pinged, this_cpu, cpu, CFD_SEQ_PINGED);
} else {
cfd_seq_store(pcpu->seq_noipi, this_cpu, cpu, CFD_SEQ_NOIPI);
}
}
#else
#define cfd_seq_store(var, src, dst, type)
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)
{
#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
if (static_branch_unlikely(&csdlock_debug_extended)) {
unsigned int type;
type = CSD_TYPE(container_of(node, call_single_data_t,
node.llist));
if (type == CSD_TYPE_SYNC || type == CSD_TYPE_ASYNC) {
__smp_call_single_queue_debug(cpu, node);
return;
}
}
#endif
/*
* The list addition should be visible before sending the IPI
* handler locks the list to pull the entry off it because of
* normal cache coherency rules implied by spinlocks.
*
* 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);
func(info);
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)
{
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->gotipi, CFD_SEQ_NOCPU,
smp_processor_id(), CFD_SEQ_GOTIPI);
__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;
lockdep_assert_irqs_disabled();
head = this_cpu_ptr(&call_single_queue);
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->handle, CFD_SEQ_NOCPU,
smp_processor_id(), CFD_SEQ_HANDLE);
entry = llist_del_all(head);
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->dequeue,
/* Special meaning of source cpu: 0 == queue empty */
entry ? CFD_SEQ_NOCPU : 0,
smp_processor_id(), CFD_SEQ_DEQUEUE);
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);
func(info);
csd_unlock(csd);
csd_lock_record(NULL);
} else {
prev = &csd->node.llist;
}
}
if (!entry) {
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->hdlend,
0, smp_processor_id(),
CFD_SEQ_HDLEND);
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);
func(info);
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)
sched_ttwu_pending(entry);
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->hdlend, CFD_SEQ_NOCPU,
smp_processor_id(), CFD_SEQ_HDLEND);
}
/**
* 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;
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->idle, CFD_SEQ_NOCPU,
smp_processor_id(), CFD_SEQ_IDLE);
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;
bool run_remote = false;
bool run_local = false;
int nr_cpus = 0;
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) {
struct cfd_percpu *pcpu = per_cpu_ptr(cfd->pcpu, cpu);
call_single_data_t *csd = &pcpu->csd;
if (cond_func && !cond_func(cpu, info))
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
cfd_seq_store(pcpu->seq_queue, this_cpu, cpu, CFD_SEQ_QUEUE);
if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) {
__cpumask_set_cpu(cpu, cfd->cpumask_ipi);
nr_cpus++;
last_cpu = cpu;
cfd_seq_store(pcpu->seq_ipi, this_cpu, cpu, CFD_SEQ_IPI);
} else {
cfd_seq_store(pcpu->seq_noipi, this_cpu, cpu, CFD_SEQ_NOIPI);
}
}
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->ping, this_cpu, CFD_SEQ_NOCPU, CFD_SEQ_PING);
/*
* 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))
arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->pinged, this_cpu, CFD_SEQ_NOCPU, CFD_SEQ_PINGED);
}
if (run_local && (!cond_func || cond_func(this_cpu, info))) {
unsigned long flags;
local_irq_save(flags);
func(info);
local_irq_restore(flags);
}
if (run_remote && wait) {
for_each_cpu(cpu, cfd->cpumask) {
call_single_data_t *csd;
csd = &per_cpu_ptr(cfd->pcpu, cpu)->csd;
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.