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

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