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TOMOYO Linux Cross Reference
Linux/kernel/padata.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * padata.c - generic interface to process data streams in parallel
  4  *
  5  * See Documentation/core-api/padata.rst for more information.
  6  *
  7  * Copyright (C) 2008, 2009 secunet Security Networks AG
  8  * Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com>
  9  *
 10  * Copyright (c) 2020 Oracle and/or its affiliates.
 11  * Author: Daniel Jordan <daniel.m.jordan@oracle.com>
 12  *
 13  * This program is free software; you can redistribute it and/or modify it
 14  * under the terms and conditions of the GNU General Public License,
 15  * version 2, as published by the Free Software Foundation.
 16  *
 17  * This program is distributed in the hope it will be useful, but WITHOUT
 18  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 19  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 20  * more details.
 21  *
 22  * You should have received a copy of the GNU General Public License along with
 23  * this program; if not, write to the Free Software Foundation, Inc.,
 24  * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 25  */
 26 
 27 #include <linux/completion.h>
 28 #include <linux/export.h>
 29 #include <linux/cpumask.h>
 30 #include <linux/err.h>
 31 #include <linux/cpu.h>
 32 #include <linux/padata.h>
 33 #include <linux/mutex.h>
 34 #include <linux/sched.h>
 35 #include <linux/slab.h>
 36 #include <linux/sysfs.h>
 37 #include <linux/rcupdate.h>
 38 
 39 #define PADATA_WORK_ONSTACK     1       /* Work's memory is on stack */
 40 
 41 struct padata_work {
 42         struct work_struct      pw_work;
 43         struct list_head        pw_list;  /* padata_free_works linkage */
 44         void                    *pw_data;
 45 };
 46 
 47 static DEFINE_SPINLOCK(padata_works_lock);
 48 static struct padata_work *padata_works;
 49 static LIST_HEAD(padata_free_works);
 50 
 51 struct padata_mt_job_state {
 52         spinlock_t              lock;
 53         struct completion       completion;
 54         struct padata_mt_job    *job;
 55         int                     nworks;
 56         int                     nworks_fini;
 57         unsigned long           chunk_size;
 58 };
 59 
 60 static void padata_free_pd(struct parallel_data *pd);
 61 static void __init padata_mt_helper(struct work_struct *work);
 62 
 63 static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
 64 {
 65         int cpu, target_cpu;
 66 
 67         target_cpu = cpumask_first(pd->cpumask.pcpu);
 68         for (cpu = 0; cpu < cpu_index; cpu++)
 69                 target_cpu = cpumask_next(target_cpu, pd->cpumask.pcpu);
 70 
 71         return target_cpu;
 72 }
 73 
 74 static int padata_cpu_hash(struct parallel_data *pd, unsigned int seq_nr)
 75 {
 76         /*
 77          * Hash the sequence numbers to the cpus by taking
 78          * seq_nr mod. number of cpus in use.
 79          */
 80         int cpu_index = seq_nr % cpumask_weight(pd->cpumask.pcpu);
 81 
 82         return padata_index_to_cpu(pd, cpu_index);
 83 }
 84 
 85 static struct padata_work *padata_work_alloc(void)
 86 {
 87         struct padata_work *pw;
 88 
 89         lockdep_assert_held(&padata_works_lock);
 90 
 91         if (list_empty(&padata_free_works))
 92                 return NULL;    /* No more work items allowed to be queued. */
 93 
 94         pw = list_first_entry(&padata_free_works, struct padata_work, pw_list);
 95         list_del(&pw->pw_list);
 96         return pw;
 97 }
 98 
 99 static void padata_work_init(struct padata_work *pw, work_func_t work_fn,
100                              void *data, int flags)
101 {
102         if (flags & PADATA_WORK_ONSTACK)
103                 INIT_WORK_ONSTACK(&pw->pw_work, work_fn);
104         else
105                 INIT_WORK(&pw->pw_work, work_fn);
106         pw->pw_data = data;
107 }
108 
109 static int __init padata_work_alloc_mt(int nworks, void *data,
110                                        struct list_head *head)
111 {
112         int i;
113 
114         spin_lock(&padata_works_lock);
115         /* Start at 1 because the current task participates in the job. */
116         for (i = 1; i < nworks; ++i) {
117                 struct padata_work *pw = padata_work_alloc();
118 
119                 if (!pw)
120                         break;
121                 padata_work_init(pw, padata_mt_helper, data, 0);
122                 list_add(&pw->pw_list, head);
123         }
124         spin_unlock(&padata_works_lock);
125 
126         return i;
127 }
128 
129 static void padata_work_free(struct padata_work *pw)
130 {
131         lockdep_assert_held(&padata_works_lock);
132         list_add(&pw->pw_list, &padata_free_works);
133 }
134 
135 static void __init padata_works_free(struct list_head *works)
136 {
137         struct padata_work *cur, *next;
138 
139         if (list_empty(works))
140                 return;
141 
142         spin_lock(&padata_works_lock);
143         list_for_each_entry_safe(cur, next, works, pw_list) {
144                 list_del(&cur->pw_list);
145                 padata_work_free(cur);
146         }
147         spin_unlock(&padata_works_lock);
148 }
149 
150 static void padata_parallel_worker(struct work_struct *parallel_work)
151 {
152         struct padata_work *pw = container_of(parallel_work, struct padata_work,
153                                               pw_work);
154         struct padata_priv *padata = pw->pw_data;
155 
156         local_bh_disable();
157         padata->parallel(padata);
158         spin_lock(&padata_works_lock);
159         padata_work_free(pw);
160         spin_unlock(&padata_works_lock);
161         local_bh_enable();
162 }
163 
164 /**
165  * padata_do_parallel - padata parallelization function
166  *
167  * @ps: padatashell
168  * @padata: object to be parallelized
169  * @cb_cpu: pointer to the CPU that the serialization callback function should
170  *          run on.  If it's not in the serial cpumask of @pinst
171  *          (i.e. cpumask.cbcpu), this function selects a fallback CPU and if
172  *          none found, returns -EINVAL.
173  *
174  * The parallelization callback function will run with BHs off.
175  * Note: Every object which is parallelized by padata_do_parallel
176  * must be seen by padata_do_serial.
177  *
178  * Return: 0 on success or else negative error code.
179  */
180 int padata_do_parallel(struct padata_shell *ps,
181                        struct padata_priv *padata, int *cb_cpu)
182 {
183         struct padata_instance *pinst = ps->pinst;
184         int i, cpu, cpu_index, err;
185         struct parallel_data *pd;
186         struct padata_work *pw;
187 
188         rcu_read_lock_bh();
189 
190         pd = rcu_dereference_bh(ps->pd);
191 
192         err = -EINVAL;
193         if (!(pinst->flags & PADATA_INIT) || pinst->flags & PADATA_INVALID)
194                 goto out;
195 
196         if (!cpumask_test_cpu(*cb_cpu, pd->cpumask.cbcpu)) {
197                 if (!cpumask_weight(pd->cpumask.cbcpu))
198                         goto out;
199 
200                 /* Select an alternate fallback CPU and notify the caller. */
201                 cpu_index = *cb_cpu % cpumask_weight(pd->cpumask.cbcpu);
202 
203                 cpu = cpumask_first(pd->cpumask.cbcpu);
204                 for (i = 0; i < cpu_index; i++)
205                         cpu = cpumask_next(cpu, pd->cpumask.cbcpu);
206 
207                 *cb_cpu = cpu;
208         }
209 
210         err =  -EBUSY;
211         if ((pinst->flags & PADATA_RESET))
212                 goto out;
213 
214         atomic_inc(&pd->refcnt);
215         padata->pd = pd;
216         padata->cb_cpu = *cb_cpu;
217 
218         spin_lock(&padata_works_lock);
219         padata->seq_nr = ++pd->seq_nr;
220         pw = padata_work_alloc();
221         spin_unlock(&padata_works_lock);
222 
223         rcu_read_unlock_bh();
224 
225         if (pw) {
226                 padata_work_init(pw, padata_parallel_worker, padata, 0);
227                 queue_work(pinst->parallel_wq, &pw->pw_work);
228         } else {
229                 /* Maximum works limit exceeded, run in the current task. */
230                 padata->parallel(padata);
231         }
232 
233         return 0;
234 out:
235         rcu_read_unlock_bh();
236 
237         return err;
238 }
239 EXPORT_SYMBOL(padata_do_parallel);
240 
241 /*
242  * padata_find_next - Find the next object that needs serialization.
243  *
244  * Return:
245  * * A pointer to the control struct of the next object that needs
246  *   serialization, if present in one of the percpu reorder queues.
247  * * NULL, if the next object that needs serialization will
248  *   be parallel processed by another cpu and is not yet present in
249  *   the cpu's reorder queue.
250  */
251 static struct padata_priv *padata_find_next(struct parallel_data *pd,
252                                             bool remove_object)
253 {
254         struct padata_priv *padata;
255         struct padata_list *reorder;
256         int cpu = pd->cpu;
257 
258         reorder = per_cpu_ptr(pd->reorder_list, cpu);
259 
260         spin_lock(&reorder->lock);
261         if (list_empty(&reorder->list)) {
262                 spin_unlock(&reorder->lock);
263                 return NULL;
264         }
265 
266         padata = list_entry(reorder->list.next, struct padata_priv, list);
267 
268         /*
269          * Checks the rare case where two or more parallel jobs have hashed to
270          * the same CPU and one of the later ones finishes first.
271          */
272         if (padata->seq_nr != pd->processed) {
273                 spin_unlock(&reorder->lock);
274                 return NULL;
275         }
276 
277         if (remove_object) {
278                 list_del_init(&padata->list);
279                 ++pd->processed;
280                 pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu, -1, false);
281         }
282 
283         spin_unlock(&reorder->lock);
284         return padata;
285 }
286 
287 static void padata_reorder(struct parallel_data *pd)
288 {
289         struct padata_instance *pinst = pd->ps->pinst;
290         int cb_cpu;
291         struct padata_priv *padata;
292         struct padata_serial_queue *squeue;
293         struct padata_list *reorder;
294 
295         /*
296          * We need to ensure that only one cpu can work on dequeueing of
297          * the reorder queue the time. Calculating in which percpu reorder
298          * queue the next object will arrive takes some time. A spinlock
299          * would be highly contended. Also it is not clear in which order
300          * the objects arrive to the reorder queues. So a cpu could wait to
301          * get the lock just to notice that there is nothing to do at the
302          * moment. Therefore we use a trylock and let the holder of the lock
303          * care for all the objects enqueued during the holdtime of the lock.
304          */
305         if (!spin_trylock_bh(&pd->lock))
306                 return;
307 
308         while (1) {
309                 padata = padata_find_next(pd, true);
310 
311                 /*
312                  * If the next object that needs serialization is parallel
313                  * processed by another cpu and is still on it's way to the
314                  * cpu's reorder queue, nothing to do for now.
315                  */
316                 if (!padata)
317                         break;
318 
319                 cb_cpu = padata->cb_cpu;
320                 squeue = per_cpu_ptr(pd->squeue, cb_cpu);
321 
322                 spin_lock(&squeue->serial.lock);
323                 list_add_tail(&padata->list, &squeue->serial.list);
324                 spin_unlock(&squeue->serial.lock);
325 
326                 queue_work_on(cb_cpu, pinst->serial_wq, &squeue->work);
327         }
328 
329         spin_unlock_bh(&pd->lock);
330 
331         /*
332          * The next object that needs serialization might have arrived to
333          * the reorder queues in the meantime.
334          *
335          * Ensure reorder queue is read after pd->lock is dropped so we see
336          * new objects from another task in padata_do_serial.  Pairs with
337          * smp_mb in padata_do_serial.
338          */
339         smp_mb();
340 
341         reorder = per_cpu_ptr(pd->reorder_list, pd->cpu);
342         if (!list_empty(&reorder->list) && padata_find_next(pd, false))
343                 queue_work(pinst->serial_wq, &pd->reorder_work);
344 }
345 
346 static void invoke_padata_reorder(struct work_struct *work)
347 {
348         struct parallel_data *pd;
349 
350         local_bh_disable();
351         pd = container_of(work, struct parallel_data, reorder_work);
352         padata_reorder(pd);
353         local_bh_enable();
354 }
355 
356 static void padata_serial_worker(struct work_struct *serial_work)
357 {
358         struct padata_serial_queue *squeue;
359         struct parallel_data *pd;
360         LIST_HEAD(local_list);
361         int cnt;
362 
363         local_bh_disable();
364         squeue = container_of(serial_work, struct padata_serial_queue, work);
365         pd = squeue->pd;
366 
367         spin_lock(&squeue->serial.lock);
368         list_replace_init(&squeue->serial.list, &local_list);
369         spin_unlock(&squeue->serial.lock);
370 
371         cnt = 0;
372 
373         while (!list_empty(&local_list)) {
374                 struct padata_priv *padata;
375 
376                 padata = list_entry(local_list.next,
377                                     struct padata_priv, list);
378 
379                 list_del_init(&padata->list);
380 
381                 padata->serial(padata);
382                 cnt++;
383         }
384         local_bh_enable();
385 
386         if (atomic_sub_and_test(cnt, &pd->refcnt))
387                 padata_free_pd(pd);
388 }
389 
390 /**
391  * padata_do_serial - padata serialization function
392  *
393  * @padata: object to be serialized.
394  *
395  * padata_do_serial must be called for every parallelized object.
396  * The serialization callback function will run with BHs off.
397  */
398 void padata_do_serial(struct padata_priv *padata)
399 {
400         struct parallel_data *pd = padata->pd;
401         int hashed_cpu = padata_cpu_hash(pd, padata->seq_nr);
402         struct padata_list *reorder = per_cpu_ptr(pd->reorder_list, hashed_cpu);
403         struct padata_priv *cur;
404 
405         spin_lock(&reorder->lock);
406         /* Sort in ascending order of sequence number. */
407         list_for_each_entry_reverse(cur, &reorder->list, list)
408                 if (cur->seq_nr < padata->seq_nr)
409                         break;
410         list_add(&padata->list, &cur->list);
411         spin_unlock(&reorder->lock);
412 
413         /*
414          * Ensure the addition to the reorder list is ordered correctly
415          * with the trylock of pd->lock in padata_reorder.  Pairs with smp_mb
416          * in padata_reorder.
417          */
418         smp_mb();
419 
420         padata_reorder(pd);
421 }
422 EXPORT_SYMBOL(padata_do_serial);
423 
424 static int padata_setup_cpumasks(struct padata_instance *pinst)
425 {
426         struct workqueue_attrs *attrs;
427         int err;
428 
429         attrs = alloc_workqueue_attrs();
430         if (!attrs)
431                 return -ENOMEM;
432 
433         /* Restrict parallel_wq workers to pd->cpumask.pcpu. */
434         cpumask_copy(attrs->cpumask, pinst->cpumask.pcpu);
435         err = apply_workqueue_attrs(pinst->parallel_wq, attrs);
436         free_workqueue_attrs(attrs);
437 
438         return err;
439 }
440 
441 static void __init padata_mt_helper(struct work_struct *w)
442 {
443         struct padata_work *pw = container_of(w, struct padata_work, pw_work);
444         struct padata_mt_job_state *ps = pw->pw_data;
445         struct padata_mt_job *job = ps->job;
446         bool done;
447 
448         spin_lock(&ps->lock);
449 
450         while (job->size > 0) {
451                 unsigned long start, size, end;
452 
453                 start = job->start;
454                 /* So end is chunk size aligned if enough work remains. */
455                 size = roundup(start + 1, ps->chunk_size) - start;
456                 size = min(size, job->size);
457                 end = start + size;
458 
459                 job->start = end;
460                 job->size -= size;
461 
462                 spin_unlock(&ps->lock);
463                 job->thread_fn(start, end, job->fn_arg);
464                 spin_lock(&ps->lock);
465         }
466 
467         ++ps->nworks_fini;
468         done = (ps->nworks_fini == ps->nworks);
469         spin_unlock(&ps->lock);
470 
471         if (done)
472                 complete(&ps->completion);
473 }
474 
475 /**
476  * padata_do_multithreaded - run a multithreaded job
477  * @job: Description of the job.
478  *
479  * See the definition of struct padata_mt_job for more details.
480  */
481 void __init padata_do_multithreaded(struct padata_mt_job *job)
482 {
483         /* In case threads finish at different times. */
484         static const unsigned long load_balance_factor = 4;
485         struct padata_work my_work, *pw;
486         struct padata_mt_job_state ps;
487         LIST_HEAD(works);
488         int nworks;
489 
490         if (job->size == 0)
491                 return;
492 
493         /* Ensure at least one thread when size < min_chunk. */
494         nworks = max(job->size / job->min_chunk, 1ul);
495         nworks = min(nworks, job->max_threads);
496 
497         if (nworks == 1) {
498                 /* Single thread, no coordination needed, cut to the chase. */
499                 job->thread_fn(job->start, job->start + job->size, job->fn_arg);
500                 return;
501         }
502 
503         spin_lock_init(&ps.lock);
504         init_completion(&ps.completion);
505         ps.job         = job;
506         ps.nworks      = padata_work_alloc_mt(nworks, &ps, &works);
507         ps.nworks_fini = 0;
508 
509         /*
510          * Chunk size is the amount of work a helper does per call to the
511          * thread function.  Load balance large jobs between threads by
512          * increasing the number of chunks, guarantee at least the minimum
513          * chunk size from the caller, and honor the caller's alignment.
514          */
515         ps.chunk_size = job->size / (ps.nworks * load_balance_factor);
516         ps.chunk_size = max(ps.chunk_size, job->min_chunk);
517         ps.chunk_size = roundup(ps.chunk_size, job->align);
518 
519         list_for_each_entry(pw, &works, pw_list)
520                 queue_work(system_unbound_wq, &pw->pw_work);
521 
522         /* Use the current thread, which saves starting a workqueue worker. */
523         padata_work_init(&my_work, padata_mt_helper, &ps, PADATA_WORK_ONSTACK);
524         padata_mt_helper(&my_work.pw_work);
525 
526         /* Wait for all the helpers to finish. */
527         wait_for_completion(&ps.completion);
528 
529         destroy_work_on_stack(&my_work.pw_work);
530         padata_works_free(&works);
531 }
532 
533 static void __padata_list_init(struct padata_list *pd_list)
534 {
535         INIT_LIST_HEAD(&pd_list->list);
536         spin_lock_init(&pd_list->lock);
537 }
538 
539 /* Initialize all percpu queues used by serial workers */
540 static void padata_init_squeues(struct parallel_data *pd)
541 {
542         int cpu;
543         struct padata_serial_queue *squeue;
544 
545         for_each_cpu(cpu, pd->cpumask.cbcpu) {
546                 squeue = per_cpu_ptr(pd->squeue, cpu);
547                 squeue->pd = pd;
548                 __padata_list_init(&squeue->serial);
549                 INIT_WORK(&squeue->work, padata_serial_worker);
550         }
551 }
552 
553 /* Initialize per-CPU reorder lists */
554 static void padata_init_reorder_list(struct parallel_data *pd)
555 {
556         int cpu;
557         struct padata_list *list;
558 
559         for_each_cpu(cpu, pd->cpumask.pcpu) {
560                 list = per_cpu_ptr(pd->reorder_list, cpu);
561                 __padata_list_init(list);
562         }
563 }
564 
565 /* Allocate and initialize the internal cpumask dependend resources. */
566 static struct parallel_data *padata_alloc_pd(struct padata_shell *ps)
567 {
568         struct padata_instance *pinst = ps->pinst;
569         struct parallel_data *pd;
570 
571         pd = kzalloc(sizeof(struct parallel_data), GFP_KERNEL);
572         if (!pd)
573                 goto err;
574 
575         pd->reorder_list = alloc_percpu(struct padata_list);
576         if (!pd->reorder_list)
577                 goto err_free_pd;
578 
579         pd->squeue = alloc_percpu(struct padata_serial_queue);
580         if (!pd->squeue)
581                 goto err_free_reorder_list;
582 
583         pd->ps = ps;
584 
585         if (!alloc_cpumask_var(&pd->cpumask.pcpu, GFP_KERNEL))
586                 goto err_free_squeue;
587         if (!alloc_cpumask_var(&pd->cpumask.cbcpu, GFP_KERNEL))
588                 goto err_free_pcpu;
589 
590         cpumask_and(pd->cpumask.pcpu, pinst->cpumask.pcpu, cpu_online_mask);
591         cpumask_and(pd->cpumask.cbcpu, pinst->cpumask.cbcpu, cpu_online_mask);
592 
593         padata_init_reorder_list(pd);
594         padata_init_squeues(pd);
595         pd->seq_nr = -1;
596         atomic_set(&pd->refcnt, 1);
597         spin_lock_init(&pd->lock);
598         pd->cpu = cpumask_first(pd->cpumask.pcpu);
599         INIT_WORK(&pd->reorder_work, invoke_padata_reorder);
600 
601         return pd;
602 
603 err_free_pcpu:
604         free_cpumask_var(pd->cpumask.pcpu);
605 err_free_squeue:
606         free_percpu(pd->squeue);
607 err_free_reorder_list:
608         free_percpu(pd->reorder_list);
609 err_free_pd:
610         kfree(pd);
611 err:
612         return NULL;
613 }
614 
615 static void padata_free_pd(struct parallel_data *pd)
616 {
617         free_cpumask_var(pd->cpumask.pcpu);
618         free_cpumask_var(pd->cpumask.cbcpu);
619         free_percpu(pd->reorder_list);
620         free_percpu(pd->squeue);
621         kfree(pd);
622 }
623 
624 static void __padata_start(struct padata_instance *pinst)
625 {
626         pinst->flags |= PADATA_INIT;
627 }
628 
629 static void __padata_stop(struct padata_instance *pinst)
630 {
631         if (!(pinst->flags & PADATA_INIT))
632                 return;
633 
634         pinst->flags &= ~PADATA_INIT;
635 
636         synchronize_rcu();
637 }
638 
639 /* Replace the internal control structure with a new one. */
640 static int padata_replace_one(struct padata_shell *ps)
641 {
642         struct parallel_data *pd_new;
643 
644         pd_new = padata_alloc_pd(ps);
645         if (!pd_new)
646                 return -ENOMEM;
647 
648         ps->opd = rcu_dereference_protected(ps->pd, 1);
649         rcu_assign_pointer(ps->pd, pd_new);
650 
651         return 0;
652 }
653 
654 static int padata_replace(struct padata_instance *pinst)
655 {
656         struct padata_shell *ps;
657         int err = 0;
658 
659         pinst->flags |= PADATA_RESET;
660 
661         list_for_each_entry(ps, &pinst->pslist, list) {
662                 err = padata_replace_one(ps);
663                 if (err)
664                         break;
665         }
666 
667         synchronize_rcu();
668 
669         list_for_each_entry_continue_reverse(ps, &pinst->pslist, list)
670                 if (atomic_dec_and_test(&ps->opd->refcnt))
671                         padata_free_pd(ps->opd);
672 
673         pinst->flags &= ~PADATA_RESET;
674 
675         return err;
676 }
677 
678 /* If cpumask contains no active cpu, we mark the instance as invalid. */
679 static bool padata_validate_cpumask(struct padata_instance *pinst,
680                                     const struct cpumask *cpumask)
681 {
682         if (!cpumask_intersects(cpumask, cpu_online_mask)) {
683                 pinst->flags |= PADATA_INVALID;
684                 return false;
685         }
686 
687         pinst->flags &= ~PADATA_INVALID;
688         return true;
689 }
690 
691 static int __padata_set_cpumasks(struct padata_instance *pinst,
692                                  cpumask_var_t pcpumask,
693                                  cpumask_var_t cbcpumask)
694 {
695         int valid;
696         int err;
697 
698         valid = padata_validate_cpumask(pinst, pcpumask);
699         if (!valid) {
700                 __padata_stop(pinst);
701                 goto out_replace;
702         }
703 
704         valid = padata_validate_cpumask(pinst, cbcpumask);
705         if (!valid)
706                 __padata_stop(pinst);
707 
708 out_replace:
709         cpumask_copy(pinst->cpumask.pcpu, pcpumask);
710         cpumask_copy(pinst->cpumask.cbcpu, cbcpumask);
711 
712         err = padata_setup_cpumasks(pinst) ?: padata_replace(pinst);
713 
714         if (valid)
715                 __padata_start(pinst);
716 
717         return err;
718 }
719 
720 /**
721  * padata_set_cpumask - Sets specified by @cpumask_type cpumask to the value
722  *                      equivalent to @cpumask.
723  * @pinst: padata instance
724  * @cpumask_type: PADATA_CPU_SERIAL or PADATA_CPU_PARALLEL corresponding
725  *                to parallel and serial cpumasks respectively.
726  * @cpumask: the cpumask to use
727  *
728  * Return: 0 on success or negative error code
729  */
730 int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
731                        cpumask_var_t cpumask)
732 {
733         struct cpumask *serial_mask, *parallel_mask;
734         int err = -EINVAL;
735 
736         get_online_cpus();
737         mutex_lock(&pinst->lock);
738 
739         switch (cpumask_type) {
740         case PADATA_CPU_PARALLEL:
741                 serial_mask = pinst->cpumask.cbcpu;
742                 parallel_mask = cpumask;
743                 break;
744         case PADATA_CPU_SERIAL:
745                 parallel_mask = pinst->cpumask.pcpu;
746                 serial_mask = cpumask;
747                 break;
748         default:
749                  goto out;
750         }
751 
752         err =  __padata_set_cpumasks(pinst, parallel_mask, serial_mask);
753 
754 out:
755         mutex_unlock(&pinst->lock);
756         put_online_cpus();
757 
758         return err;
759 }
760 EXPORT_SYMBOL(padata_set_cpumask);
761 
762 #ifdef CONFIG_HOTPLUG_CPU
763 
764 static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
765 {
766         int err = 0;
767 
768         if (cpumask_test_cpu(cpu, cpu_online_mask)) {
769                 err = padata_replace(pinst);
770 
771                 if (padata_validate_cpumask(pinst, pinst->cpumask.pcpu) &&
772                     padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))
773                         __padata_start(pinst);
774         }
775 
776         return err;
777 }
778 
779 static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
780 {
781         int err = 0;
782 
783         if (!cpumask_test_cpu(cpu, cpu_online_mask)) {
784                 if (!padata_validate_cpumask(pinst, pinst->cpumask.pcpu) ||
785                     !padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))
786                         __padata_stop(pinst);
787 
788                 err = padata_replace(pinst);
789         }
790 
791         return err;
792 }
793 
794 static inline int pinst_has_cpu(struct padata_instance *pinst, int cpu)
795 {
796         return cpumask_test_cpu(cpu, pinst->cpumask.pcpu) ||
797                 cpumask_test_cpu(cpu, pinst->cpumask.cbcpu);
798 }
799 
800 static int padata_cpu_online(unsigned int cpu, struct hlist_node *node)
801 {
802         struct padata_instance *pinst;
803         int ret;
804 
805         pinst = hlist_entry_safe(node, struct padata_instance, cpu_online_node);
806         if (!pinst_has_cpu(pinst, cpu))
807                 return 0;
808 
809         mutex_lock(&pinst->lock);
810         ret = __padata_add_cpu(pinst, cpu);
811         mutex_unlock(&pinst->lock);
812         return ret;
813 }
814 
815 static int padata_cpu_dead(unsigned int cpu, struct hlist_node *node)
816 {
817         struct padata_instance *pinst;
818         int ret;
819 
820         pinst = hlist_entry_safe(node, struct padata_instance, cpu_dead_node);
821         if (!pinst_has_cpu(pinst, cpu))
822                 return 0;
823 
824         mutex_lock(&pinst->lock);
825         ret = __padata_remove_cpu(pinst, cpu);
826         mutex_unlock(&pinst->lock);
827         return ret;
828 }
829 
830 static enum cpuhp_state hp_online;
831 #endif
832 
833 static void __padata_free(struct padata_instance *pinst)
834 {
835 #ifdef CONFIG_HOTPLUG_CPU
836         cpuhp_state_remove_instance_nocalls(CPUHP_PADATA_DEAD,
837                                             &pinst->cpu_dead_node);
838         cpuhp_state_remove_instance_nocalls(hp_online, &pinst->cpu_online_node);
839 #endif
840 
841         WARN_ON(!list_empty(&pinst->pslist));
842 
843         free_cpumask_var(pinst->cpumask.pcpu);
844         free_cpumask_var(pinst->cpumask.cbcpu);
845         destroy_workqueue(pinst->serial_wq);
846         destroy_workqueue(pinst->parallel_wq);
847         kfree(pinst);
848 }
849 
850 #define kobj2pinst(_kobj)                                       \
851         container_of(_kobj, struct padata_instance, kobj)
852 #define attr2pentry(_attr)                                      \
853         container_of(_attr, struct padata_sysfs_entry, attr)
854 
855 static void padata_sysfs_release(struct kobject *kobj)
856 {
857         struct padata_instance *pinst = kobj2pinst(kobj);
858         __padata_free(pinst);
859 }
860 
861 struct padata_sysfs_entry {
862         struct attribute attr;
863         ssize_t (*show)(struct padata_instance *, struct attribute *, char *);
864         ssize_t (*store)(struct padata_instance *, struct attribute *,
865                          const char *, size_t);
866 };
867 
868 static ssize_t show_cpumask(struct padata_instance *pinst,
869                             struct attribute *attr,  char *buf)
870 {
871         struct cpumask *cpumask;
872         ssize_t len;
873 
874         mutex_lock(&pinst->lock);
875         if (!strcmp(attr->name, "serial_cpumask"))
876                 cpumask = pinst->cpumask.cbcpu;
877         else
878                 cpumask = pinst->cpumask.pcpu;
879 
880         len = snprintf(buf, PAGE_SIZE, "%*pb\n",
881                        nr_cpu_ids, cpumask_bits(cpumask));
882         mutex_unlock(&pinst->lock);
883         return len < PAGE_SIZE ? len : -EINVAL;
884 }
885 
886 static ssize_t store_cpumask(struct padata_instance *pinst,
887                              struct attribute *attr,
888                              const char *buf, size_t count)
889 {
890         cpumask_var_t new_cpumask;
891         ssize_t ret;
892         int mask_type;
893 
894         if (!alloc_cpumask_var(&new_cpumask, GFP_KERNEL))
895                 return -ENOMEM;
896 
897         ret = bitmap_parse(buf, count, cpumask_bits(new_cpumask),
898                            nr_cpumask_bits);
899         if (ret < 0)
900                 goto out;
901 
902         mask_type = !strcmp(attr->name, "serial_cpumask") ?
903                 PADATA_CPU_SERIAL : PADATA_CPU_PARALLEL;
904         ret = padata_set_cpumask(pinst, mask_type, new_cpumask);
905         if (!ret)
906                 ret = count;
907 
908 out:
909         free_cpumask_var(new_cpumask);
910         return ret;
911 }
912 
913 #define PADATA_ATTR_RW(_name, _show_name, _store_name)          \
914         static struct padata_sysfs_entry _name##_attr =         \
915                 __ATTR(_name, 0644, _show_name, _store_name)
916 #define PADATA_ATTR_RO(_name, _show_name)               \
917         static struct padata_sysfs_entry _name##_attr = \
918                 __ATTR(_name, 0400, _show_name, NULL)
919 
920 PADATA_ATTR_RW(serial_cpumask, show_cpumask, store_cpumask);
921 PADATA_ATTR_RW(parallel_cpumask, show_cpumask, store_cpumask);
922 
923 /*
924  * Padata sysfs provides the following objects:
925  * serial_cpumask   [RW] - cpumask for serial workers
926  * parallel_cpumask [RW] - cpumask for parallel workers
927  */
928 static struct attribute *padata_default_attrs[] = {
929         &serial_cpumask_attr.attr,
930         &parallel_cpumask_attr.attr,
931         NULL,
932 };
933 ATTRIBUTE_GROUPS(padata_default);
934 
935 static ssize_t padata_sysfs_show(struct kobject *kobj,
936                                  struct attribute *attr, char *buf)
937 {
938         struct padata_instance *pinst;
939         struct padata_sysfs_entry *pentry;
940         ssize_t ret = -EIO;
941 
942         pinst = kobj2pinst(kobj);
943         pentry = attr2pentry(attr);
944         if (pentry->show)
945                 ret = pentry->show(pinst, attr, buf);
946 
947         return ret;
948 }
949 
950 static ssize_t padata_sysfs_store(struct kobject *kobj, struct attribute *attr,
951                                   const char *buf, size_t count)
952 {
953         struct padata_instance *pinst;
954         struct padata_sysfs_entry *pentry;
955         ssize_t ret = -EIO;
956 
957         pinst = kobj2pinst(kobj);
958         pentry = attr2pentry(attr);
959         if (pentry->show)
960                 ret = pentry->store(pinst, attr, buf, count);
961 
962         return ret;
963 }
964 
965 static const struct sysfs_ops padata_sysfs_ops = {
966         .show = padata_sysfs_show,
967         .store = padata_sysfs_store,
968 };
969 
970 static struct kobj_type padata_attr_type = {
971         .sysfs_ops = &padata_sysfs_ops,
972         .default_groups = padata_default_groups,
973         .release = padata_sysfs_release,
974 };
975 
976 /**
977  * padata_alloc - allocate and initialize a padata instance
978  * @name: used to identify the instance
979  *
980  * Return: new instance on success, NULL on error
981  */
982 struct padata_instance *padata_alloc(const char *name)
983 {
984         struct padata_instance *pinst;
985 
986         pinst = kzalloc(sizeof(struct padata_instance), GFP_KERNEL);
987         if (!pinst)
988                 goto err;
989 
990         pinst->parallel_wq = alloc_workqueue("%s_parallel", WQ_UNBOUND, 0,
991                                              name);
992         if (!pinst->parallel_wq)
993                 goto err_free_inst;
994 
995         get_online_cpus();
996 
997         pinst->serial_wq = alloc_workqueue("%s_serial", WQ_MEM_RECLAIM |
998                                            WQ_CPU_INTENSIVE, 1, name);
999         if (!pinst->serial_wq)
1000                 goto err_put_cpus;
1001 
1002         if (!alloc_cpumask_var(&pinst->cpumask.pcpu, GFP_KERNEL))
1003                 goto err_free_serial_wq;
1004         if (!alloc_cpumask_var(&pinst->cpumask.cbcpu, GFP_KERNEL)) {
1005                 free_cpumask_var(pinst->cpumask.pcpu);
1006                 goto err_free_serial_wq;
1007         }
1008 
1009         INIT_LIST_HEAD(&pinst->pslist);
1010 
1011         cpumask_copy(pinst->cpumask.pcpu, cpu_possible_mask);
1012         cpumask_copy(pinst->cpumask.cbcpu, cpu_possible_mask);
1013 
1014         if (padata_setup_cpumasks(pinst))
1015                 goto err_free_masks;
1016 
1017         __padata_start(pinst);
1018 
1019         kobject_init(&pinst->kobj, &padata_attr_type);
1020         mutex_init(&pinst->lock);
1021 
1022 #ifdef CONFIG_HOTPLUG_CPU
1023         cpuhp_state_add_instance_nocalls_cpuslocked(hp_online,
1024                                                     &pinst->cpu_online_node);
1025         cpuhp_state_add_instance_nocalls_cpuslocked(CPUHP_PADATA_DEAD,
1026                                                     &pinst->cpu_dead_node);
1027 #endif
1028 
1029         put_online_cpus();
1030 
1031         return pinst;
1032 
1033 err_free_masks:
1034         free_cpumask_var(pinst->cpumask.pcpu);
1035         free_cpumask_var(pinst->cpumask.cbcpu);
1036 err_free_serial_wq:
1037         destroy_workqueue(pinst->serial_wq);
1038 err_put_cpus:
1039         put_online_cpus();
1040         destroy_workqueue(pinst->parallel_wq);
1041 err_free_inst:
1042         kfree(pinst);
1043 err:
1044         return NULL;
1045 }
1046 EXPORT_SYMBOL(padata_alloc);
1047 
1048 /**
1049  * padata_free - free a padata instance
1050  *
1051  * @pinst: padata instance to free
1052  */
1053 void padata_free(struct padata_instance *pinst)
1054 {
1055         kobject_put(&pinst->kobj);
1056 }
1057 EXPORT_SYMBOL(padata_free);
1058 
1059 /**
1060  * padata_alloc_shell - Allocate and initialize padata shell.
1061  *
1062  * @pinst: Parent padata_instance object.
1063  *
1064  * Return: new shell on success, NULL on error
1065  */
1066 struct padata_shell *padata_alloc_shell(struct padata_instance *pinst)
1067 {
1068         struct parallel_data *pd;
1069         struct padata_shell *ps;
1070 
1071         ps = kzalloc(sizeof(*ps), GFP_KERNEL);
1072         if (!ps)
1073                 goto out;
1074 
1075         ps->pinst = pinst;
1076 
1077         get_online_cpus();
1078         pd = padata_alloc_pd(ps);
1079         put_online_cpus();
1080 
1081         if (!pd)
1082                 goto out_free_ps;
1083 
1084         mutex_lock(&pinst->lock);
1085         RCU_INIT_POINTER(ps->pd, pd);
1086         list_add(&ps->list, &pinst->pslist);
1087         mutex_unlock(&pinst->lock);
1088 
1089         return ps;
1090 
1091 out_free_ps:
1092         kfree(ps);
1093 out:
1094         return NULL;
1095 }
1096 EXPORT_SYMBOL(padata_alloc_shell);
1097 
1098 /**
1099  * padata_free_shell - free a padata shell
1100  *
1101  * @ps: padata shell to free
1102  */
1103 void padata_free_shell(struct padata_shell *ps)
1104 {
1105         if (!ps)
1106                 return;
1107 
1108         mutex_lock(&ps->pinst->lock);
1109         list_del(&ps->list);
1110         padata_free_pd(rcu_dereference_protected(ps->pd, 1));
1111         mutex_unlock(&ps->pinst->lock);
1112 
1113         kfree(ps);
1114 }
1115 EXPORT_SYMBOL(padata_free_shell);
1116 
1117 void __init padata_init(void)
1118 {
1119         unsigned int i, possible_cpus;
1120 #ifdef CONFIG_HOTPLUG_CPU
1121         int ret;
1122 
1123         ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "padata:online",
1124                                       padata_cpu_online, NULL);
1125         if (ret < 0)
1126                 goto err;
1127         hp_online = ret;
1128 
1129         ret = cpuhp_setup_state_multi(CPUHP_PADATA_DEAD, "padata:dead",
1130                                       NULL, padata_cpu_dead);
1131         if (ret < 0)
1132                 goto remove_online_state;
1133 #endif
1134 
1135         possible_cpus = num_possible_cpus();
1136         padata_works = kmalloc_array(possible_cpus, sizeof(struct padata_work),
1137                                      GFP_KERNEL);
1138         if (!padata_works)
1139                 goto remove_dead_state;
1140 
1141         for (i = 0; i < possible_cpus; ++i)
1142                 list_add(&padata_works[i].pw_list, &padata_free_works);
1143 
1144         return;
1145 
1146 remove_dead_state:
1147 #ifdef CONFIG_HOTPLUG_CPU
1148         cpuhp_remove_multi_state(CPUHP_PADATA_DEAD);
1149 remove_online_state:
1150         cpuhp_remove_multi_state(hp_online);
1151 err:
1152 #endif
1153         pr_warn("padata: initialization failed\n");
1154 }
1155 

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