2 * Generic helpers for smp ipi calls
4 * (C) Jens Axboe <jens.axboe@oracle.com> 2008
7 #include <linux/init.h>
8 #include <linux/module.h>
9 #include <linux/percpu.h>
10 #include <linux/rcupdate.h>
11 #include <linux/smp.h>
13 static DEFINE_PER_CPU(struct call_single_queue
, call_single_queue
);
14 static LIST_HEAD(call_function_queue
);
15 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(call_function_lock
);
19 CSD_FLAG_ALLOC
= 0x02,
22 struct call_function_data
{
23 struct call_single_data csd
;
27 struct rcu_head rcu_head
;
30 struct call_single_queue
{
31 struct list_head list
;
35 void __cpuinit
init_call_single_data(void)
39 for_each_possible_cpu(i
) {
40 struct call_single_queue
*q
= &per_cpu(call_single_queue
, i
);
42 spin_lock_init(&q
->lock
);
43 INIT_LIST_HEAD(&q
->list
);
47 static void csd_flag_wait(struct call_single_data
*data
)
49 /* Wait for response */
52 * We need to see the flags store in the IPI handler
55 if (!(data
->flags
& CSD_FLAG_WAIT
))
62 * Insert a previously allocated call_single_data element for execution
63 * on the given CPU. data must already have ->func, ->info, and ->flags set.
65 static void generic_exec_single(int cpu
, struct call_single_data
*data
)
67 struct call_single_queue
*dst
= &per_cpu(call_single_queue
, cpu
);
68 int wait
= data
->flags
& CSD_FLAG_WAIT
, ipi
;
71 spin_lock_irqsave(&dst
->lock
, flags
);
72 ipi
= list_empty(&dst
->list
);
73 list_add_tail(&data
->list
, &dst
->list
);
74 spin_unlock_irqrestore(&dst
->lock
, flags
);
77 arch_send_call_function_single_ipi(cpu
);
83 static void rcu_free_call_data(struct rcu_head
*head
)
85 struct call_function_data
*data
;
87 data
= container_of(head
, struct call_function_data
, rcu_head
);
93 * Invoked by arch to handle an IPI for call function. Must be called with
94 * interrupts disabled.
96 void generic_smp_call_function_interrupt(void)
98 struct call_function_data
*data
;
102 * It's ok to use list_for_each_rcu() here even though we may delete
103 * 'pos', since list_del_rcu() doesn't clear ->next
106 list_for_each_entry_rcu(data
, &call_function_queue
, csd
.list
) {
109 if (!cpu_isset(cpu
, data
->cpumask
))
112 data
->csd
.func(data
->csd
.info
);
114 spin_lock(&data
->lock
);
115 cpu_clear(cpu
, data
->cpumask
);
116 WARN_ON(data
->refs
== 0);
119 spin_unlock(&data
->lock
);
124 spin_lock(&call_function_lock
);
125 list_del_rcu(&data
->csd
.list
);
126 spin_unlock(&call_function_lock
);
128 if (data
->csd
.flags
& CSD_FLAG_WAIT
) {
130 * serialize stores to data with the flag clear
134 data
->csd
.flags
&= ~CSD_FLAG_WAIT
;
136 call_rcu(&data
->rcu_head
, rcu_free_call_data
);
144 * Invoked by arch to handle an IPI for call function single. Must be called
145 * from the arch with interrupts disabled.
147 void generic_smp_call_function_single_interrupt(void)
149 struct call_single_queue
*q
= &__get_cpu_var(call_single_queue
);
153 * Need to see other stores to list head for checking whether
154 * list is empty without holding q->lock
157 while (!list_empty(&q
->list
)) {
158 unsigned int data_flags
;
161 list_replace_init(&q
->list
, &list
);
162 spin_unlock(&q
->lock
);
164 while (!list_empty(&list
)) {
165 struct call_single_data
*data
;
167 data
= list_entry(list
.next
, struct call_single_data
,
169 list_del(&data
->list
);
172 * 'data' can be invalid after this call if
173 * flags == 0 (when called through
174 * generic_exec_single(), so save them away before
177 data_flags
= data
->flags
;
179 data
->func(data
->info
);
181 if (data_flags
& CSD_FLAG_WAIT
) {
183 data
->flags
&= ~CSD_FLAG_WAIT
;
184 } else if (data_flags
& CSD_FLAG_ALLOC
)
188 * See comment on outer loop
195 * smp_call_function_single - Run a function on a specific CPU
196 * @func: The function to run. This must be fast and non-blocking.
197 * @info: An arbitrary pointer to pass to the function.
198 * @wait: If true, wait until function has completed on other CPUs.
200 * Returns 0 on success, else a negative status code. Note that @wait
201 * will be implicitly turned on in case of allocation failures, since
202 * we fall back to on-stack allocation.
204 int smp_call_function_single(int cpu
, void (*func
) (void *info
), void *info
,
207 struct call_single_data d
;
209 /* prevent preemption and reschedule on another processor */
212 /* Can deadlock when called with interrupts disabled */
213 WARN_ON(irqs_disabled());
216 local_irq_save(flags
);
218 local_irq_restore(flags
);
220 struct call_single_data
*data
= NULL
;
223 data
= kmalloc(sizeof(*data
), GFP_ATOMIC
);
225 data
->flags
= CSD_FLAG_ALLOC
;
229 data
->flags
= CSD_FLAG_WAIT
;
234 generic_exec_single(cpu
, data
);
240 EXPORT_SYMBOL(smp_call_function_single
);
243 * __smp_call_function_single(): Run a function on another CPU
244 * @cpu: The CPU to run on.
245 * @data: Pre-allocated and setup data structure
247 * Like smp_call_function_single(), but allow caller to pass in a pre-allocated
248 * data structure. Useful for embedding @data inside other structures, for
252 void __smp_call_function_single(int cpu
, struct call_single_data
*data
)
254 /* Can deadlock when called with interrupts disabled */
255 WARN_ON((data
->flags
& CSD_FLAG_WAIT
) && irqs_disabled());
257 generic_exec_single(cpu
, data
);
261 * smp_call_function_mask(): Run a function on a set of other CPUs.
262 * @mask: The set of cpus to run on.
263 * @func: The function to run. This must be fast and non-blocking.
264 * @info: An arbitrary pointer to pass to the function.
265 * @wait: If true, wait (atomically) until function has completed on other CPUs.
267 * Returns 0 on success, else a negative status code.
269 * If @wait is true, then returns once @func has returned. Note that @wait
270 * will be implicitly turned on in case of allocation failures, since
271 * we fall back to on-stack allocation.
273 * You must not call this function with disabled interrupts or from a
274 * hardware interrupt handler or from a bottom half handler. Preemption
275 * must be disabled when calling this function.
277 int smp_call_function_mask(cpumask_t mask
, void (*func
)(void *), void *info
,
280 struct call_function_data d
;
281 struct call_function_data
*data
= NULL
;
282 cpumask_t allbutself
;
286 /* Can deadlock when called with interrupts disabled */
287 WARN_ON(irqs_disabled());
289 cpu
= smp_processor_id();
290 allbutself
= cpu_online_map
;
291 cpu_clear(cpu
, allbutself
);
292 cpus_and(mask
, mask
, allbutself
);
293 num_cpus
= cpus_weight(mask
);
296 * If zero CPUs, return. If just a single CPU, turn this request
297 * into a targetted single call instead since it's faster.
301 else if (num_cpus
== 1) {
302 cpu
= first_cpu(mask
);
303 return smp_call_function_single(cpu
, func
, info
, 0, wait
);
307 data
= kmalloc(sizeof(*data
), GFP_ATOMIC
);
309 data
->csd
.flags
= CSD_FLAG_ALLOC
;
313 data
->csd
.flags
= CSD_FLAG_WAIT
;
316 spin_lock_init(&data
->lock
);
317 data
->csd
.func
= func
;
318 data
->csd
.info
= info
;
319 data
->refs
= num_cpus
;
320 data
->cpumask
= mask
;
322 spin_lock_irqsave(&call_function_lock
, flags
);
323 list_add_tail_rcu(&data
->csd
.list
, &call_function_queue
);
324 spin_unlock_irqrestore(&call_function_lock
, flags
);
326 /* Send a message to all CPUs in the map */
327 arch_send_call_function_ipi(mask
);
329 /* optionally wait for the CPUs to complete */
331 csd_flag_wait(&data
->csd
);
335 EXPORT_SYMBOL(smp_call_function_mask
);
338 * smp_call_function(): Run a function on all other CPUs.
339 * @func: The function to run. This must be fast and non-blocking.
340 * @info: An arbitrary pointer to pass to the function.
341 * @wait: If true, wait (atomically) until function has completed on other CPUs.
343 * Returns 0 on success, else a negative status code.
345 * If @wait is true, then returns once @func has returned; otherwise
346 * it returns just before the target cpu calls @func. In case of allocation
347 * failure, @wait will be implicitly turned on.
349 * You must not call this function with disabled interrupts or from a
350 * hardware interrupt handler or from a bottom half handler.
352 int smp_call_function(void (*func
)(void *), void *info
, int wait
)
357 ret
= smp_call_function_mask(cpu_online_map
, func
, info
, wait
);
361 EXPORT_SYMBOL(smp_call_function
);
363 void ipi_call_lock(void)
365 spin_lock(&call_function_lock
);
368 void ipi_call_unlock(void)
370 spin_unlock(&call_function_lock
);
373 void ipi_call_lock_irq(void)
375 spin_lock_irq(&call_function_lock
);
378 void ipi_call_unlock_irq(void)
380 spin_unlock_irq(&call_function_lock
);