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Linux/arch/powerpc/platforms/cell/spufs/sched.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /* sched.c - SPU scheduler.
  3  *
  4  * Copyright (C) IBM 2005
  5  * Author: Mark Nutter <mnutter@us.ibm.com>
  6  *
  7  * 2006-03-31   NUMA domains added.
  8  */
  9 
 10 #undef DEBUG
 11 
 12 #include <linux/errno.h>
 13 #include <linux/sched/signal.h>
 14 #include <linux/sched/loadavg.h>
 15 #include <linux/sched/rt.h>
 16 #include <linux/kernel.h>
 17 #include <linux/mm.h>
 18 #include <linux/slab.h>
 19 #include <linux/completion.h>
 20 #include <linux/vmalloc.h>
 21 #include <linux/smp.h>
 22 #include <linux/stddef.h>
 23 #include <linux/unistd.h>
 24 #include <linux/numa.h>
 25 #include <linux/mutex.h>
 26 #include <linux/notifier.h>
 27 #include <linux/kthread.h>
 28 #include <linux/pid_namespace.h>
 29 #include <linux/proc_fs.h>
 30 #include <linux/seq_file.h>
 31 
 32 #include <asm/io.h>
 33 #include <asm/mmu_context.h>
 34 #include <asm/spu.h>
 35 #include <asm/spu_csa.h>
 36 #include <asm/spu_priv1.h>
 37 #include "spufs.h"
 38 #define CREATE_TRACE_POINTS
 39 #include "sputrace.h"
 40 
 41 struct spu_prio_array {
 42         DECLARE_BITMAP(bitmap, MAX_PRIO);
 43         struct list_head runq[MAX_PRIO];
 44         spinlock_t runq_lock;
 45         int nr_waiting;
 46 };
 47 
 48 static unsigned long spu_avenrun[3];
 49 static struct spu_prio_array *spu_prio;
 50 static struct task_struct *spusched_task;
 51 static struct timer_list spusched_timer;
 52 static struct timer_list spuloadavg_timer;
 53 
 54 /*
 55  * Priority of a normal, non-rt, non-niced'd process (aka nice level 0).
 56  */
 57 #define NORMAL_PRIO             120
 58 
 59 /*
 60  * Frequency of the spu scheduler tick.  By default we do one SPU scheduler
 61  * tick for every 10 CPU scheduler ticks.
 62  */
 63 #define SPUSCHED_TICK           (10)
 64 
 65 /*
 66  * These are the 'tuning knobs' of the scheduler:
 67  *
 68  * Minimum timeslice is 5 msecs (or 1 spu scheduler tick, whichever is
 69  * larger), default timeslice is 100 msecs, maximum timeslice is 800 msecs.
 70  */
 71 #define MIN_SPU_TIMESLICE       max(5 * HZ / (1000 * SPUSCHED_TICK), 1)
 72 #define DEF_SPU_TIMESLICE       (100 * HZ / (1000 * SPUSCHED_TICK))
 73 
 74 #define SCALE_PRIO(x, prio) \
 75         max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_SPU_TIMESLICE)
 76 
 77 /*
 78  * scale user-nice values [ -20 ... 0 ... 19 ] to time slice values:
 79  * [800ms ... 100ms ... 5ms]
 80  *
 81  * The higher a thread's priority, the bigger timeslices
 82  * it gets during one round of execution. But even the lowest
 83  * priority thread gets MIN_TIMESLICE worth of execution time.
 84  */
 85 void spu_set_timeslice(struct spu_context *ctx)
 86 {
 87         if (ctx->prio < NORMAL_PRIO)
 88                 ctx->time_slice = SCALE_PRIO(DEF_SPU_TIMESLICE * 4, ctx->prio);
 89         else
 90                 ctx->time_slice = SCALE_PRIO(DEF_SPU_TIMESLICE, ctx->prio);
 91 }
 92 
 93 /*
 94  * Update scheduling information from the owning thread.
 95  */
 96 void __spu_update_sched_info(struct spu_context *ctx)
 97 {
 98         /*
 99          * assert that the context is not on the runqueue, so it is safe
100          * to change its scheduling parameters.
101          */
102         BUG_ON(!list_empty(&ctx->rq));
103 
104         /*
105          * 32-Bit assignments are atomic on powerpc, and we don't care about
106          * memory ordering here because retrieving the controlling thread is
107          * per definition racy.
108          */
109         ctx->tid = current->pid;
110 
111         /*
112          * We do our own priority calculations, so we normally want
113          * ->static_prio to start with. Unfortunately this field
114          * contains junk for threads with a realtime scheduling
115          * policy so we have to look at ->prio in this case.
116          */
117         if (rt_prio(current->prio))
118                 ctx->prio = current->prio;
119         else
120                 ctx->prio = current->static_prio;
121         ctx->policy = current->policy;
122 
123         /*
124          * TO DO: the context may be loaded, so we may need to activate
125          * it again on a different node. But it shouldn't hurt anything
126          * to update its parameters, because we know that the scheduler
127          * is not actively looking at this field, since it is not on the
128          * runqueue. The context will be rescheduled on the proper node
129          * if it is timesliced or preempted.
130          */
131         cpumask_copy(&ctx->cpus_allowed, current->cpus_ptr);
132 
133         /* Save the current cpu id for spu interrupt routing. */
134         ctx->last_ran = raw_smp_processor_id();
135 }
136 
137 void spu_update_sched_info(struct spu_context *ctx)
138 {
139         int node;
140 
141         if (ctx->state == SPU_STATE_RUNNABLE) {
142                 node = ctx->spu->node;
143 
144                 /*
145                  * Take list_mutex to sync with find_victim().
146                  */
147                 mutex_lock(&cbe_spu_info[node].list_mutex);
148                 __spu_update_sched_info(ctx);
149                 mutex_unlock(&cbe_spu_info[node].list_mutex);
150         } else {
151                 __spu_update_sched_info(ctx);
152         }
153 }
154 
155 static int __node_allowed(struct spu_context *ctx, int node)
156 {
157         if (nr_cpus_node(node)) {
158                 const struct cpumask *mask = cpumask_of_node(node);
159 
160                 if (cpumask_intersects(mask, &ctx->cpus_allowed))
161                         return 1;
162         }
163 
164         return 0;
165 }
166 
167 static int node_allowed(struct spu_context *ctx, int node)
168 {
169         int rval;
170 
171         spin_lock(&spu_prio->runq_lock);
172         rval = __node_allowed(ctx, node);
173         spin_unlock(&spu_prio->runq_lock);
174 
175         return rval;
176 }
177 
178 void do_notify_spus_active(void)
179 {
180         int node;
181 
182         /*
183          * Wake up the active spu_contexts.
184          *
185          * When the awakened processes see their "notify_active" flag is set,
186          * they will call spu_switch_notify().
187          */
188         for_each_online_node(node) {
189                 struct spu *spu;
190 
191                 mutex_lock(&cbe_spu_info[node].list_mutex);
192                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
193                         if (spu->alloc_state != SPU_FREE) {
194                                 struct spu_context *ctx = spu->ctx;
195                                 set_bit(SPU_SCHED_NOTIFY_ACTIVE,
196                                         &ctx->sched_flags);
197                                 mb();
198                                 wake_up_all(&ctx->stop_wq);
199                         }
200                 }
201                 mutex_unlock(&cbe_spu_info[node].list_mutex);
202         }
203 }
204 
205 /**
206  * spu_bind_context - bind spu context to physical spu
207  * @spu:        physical spu to bind to
208  * @ctx:        context to bind
209  */
210 static void spu_bind_context(struct spu *spu, struct spu_context *ctx)
211 {
212         spu_context_trace(spu_bind_context__enter, ctx, spu);
213 
214         spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
215 
216         if (ctx->flags & SPU_CREATE_NOSCHED)
217                 atomic_inc(&cbe_spu_info[spu->node].reserved_spus);
218 
219         ctx->stats.slb_flt_base = spu->stats.slb_flt;
220         ctx->stats.class2_intr_base = spu->stats.class2_intr;
221 
222         spu_associate_mm(spu, ctx->owner);
223 
224         spin_lock_irq(&spu->register_lock);
225         spu->ctx = ctx;
226         spu->flags = 0;
227         ctx->spu = spu;
228         ctx->ops = &spu_hw_ops;
229         spu->pid = current->pid;
230         spu->tgid = current->tgid;
231         spu->ibox_callback = spufs_ibox_callback;
232         spu->wbox_callback = spufs_wbox_callback;
233         spu->stop_callback = spufs_stop_callback;
234         spu->mfc_callback = spufs_mfc_callback;
235         spin_unlock_irq(&spu->register_lock);
236 
237         spu_unmap_mappings(ctx);
238 
239         spu_switch_log_notify(spu, ctx, SWITCH_LOG_START, 0);
240         spu_restore(&ctx->csa, spu);
241         spu->timestamp = jiffies;
242         spu_switch_notify(spu, ctx);
243         ctx->state = SPU_STATE_RUNNABLE;
244 
245         spuctx_switch_state(ctx, SPU_UTIL_USER);
246 }
247 
248 /*
249  * Must be used with the list_mutex held.
250  */
251 static inline int sched_spu(struct spu *spu)
252 {
253         BUG_ON(!mutex_is_locked(&cbe_spu_info[spu->node].list_mutex));
254 
255         return (!spu->ctx || !(spu->ctx->flags & SPU_CREATE_NOSCHED));
256 }
257 
258 static void aff_merge_remaining_ctxs(struct spu_gang *gang)
259 {
260         struct spu_context *ctx;
261 
262         list_for_each_entry(ctx, &gang->aff_list_head, aff_list) {
263                 if (list_empty(&ctx->aff_list))
264                         list_add(&ctx->aff_list, &gang->aff_list_head);
265         }
266         gang->aff_flags |= AFF_MERGED;
267 }
268 
269 static void aff_set_offsets(struct spu_gang *gang)
270 {
271         struct spu_context *ctx;
272         int offset;
273 
274         offset = -1;
275         list_for_each_entry_reverse(ctx, &gang->aff_ref_ctx->aff_list,
276                                                                 aff_list) {
277                 if (&ctx->aff_list == &gang->aff_list_head)
278                         break;
279                 ctx->aff_offset = offset--;
280         }
281 
282         offset = 0;
283         list_for_each_entry(ctx, gang->aff_ref_ctx->aff_list.prev, aff_list) {
284                 if (&ctx->aff_list == &gang->aff_list_head)
285                         break;
286                 ctx->aff_offset = offset++;
287         }
288 
289         gang->aff_flags |= AFF_OFFSETS_SET;
290 }
291 
292 static struct spu *aff_ref_location(struct spu_context *ctx, int mem_aff,
293                  int group_size, int lowest_offset)
294 {
295         struct spu *spu;
296         int node, n;
297 
298         /*
299          * TODO: A better algorithm could be used to find a good spu to be
300          *       used as reference location for the ctxs chain.
301          */
302         node = cpu_to_node(raw_smp_processor_id());
303         for (n = 0; n < MAX_NUMNODES; n++, node++) {
304                 /*
305                  * "available_spus" counts how many spus are not potentially
306                  * going to be used by other affinity gangs whose reference
307                  * context is already in place. Although this code seeks to
308                  * avoid having affinity gangs with a summed amount of
309                  * contexts bigger than the amount of spus in the node,
310                  * this may happen sporadically. In this case, available_spus
311                  * becomes negative, which is harmless.
312                  */
313                 int available_spus;
314 
315                 node = (node < MAX_NUMNODES) ? node : 0;
316                 if (!node_allowed(ctx, node))
317                         continue;
318 
319                 available_spus = 0;
320                 mutex_lock(&cbe_spu_info[node].list_mutex);
321                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
322                         if (spu->ctx && spu->ctx->gang && !spu->ctx->aff_offset
323                                         && spu->ctx->gang->aff_ref_spu)
324                                 available_spus -= spu->ctx->gang->contexts;
325                         available_spus++;
326                 }
327                 if (available_spus < ctx->gang->contexts) {
328                         mutex_unlock(&cbe_spu_info[node].list_mutex);
329                         continue;
330                 }
331 
332                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
333                         if ((!mem_aff || spu->has_mem_affinity) &&
334                                                         sched_spu(spu)) {
335                                 mutex_unlock(&cbe_spu_info[node].list_mutex);
336                                 return spu;
337                         }
338                 }
339                 mutex_unlock(&cbe_spu_info[node].list_mutex);
340         }
341         return NULL;
342 }
343 
344 static void aff_set_ref_point_location(struct spu_gang *gang)
345 {
346         int mem_aff, gs, lowest_offset;
347         struct spu_context *ctx;
348         struct spu *tmp;
349 
350         mem_aff = gang->aff_ref_ctx->flags & SPU_CREATE_AFFINITY_MEM;
351         lowest_offset = 0;
352         gs = 0;
353 
354         list_for_each_entry(tmp, &gang->aff_list_head, aff_list)
355                 gs++;
356 
357         list_for_each_entry_reverse(ctx, &gang->aff_ref_ctx->aff_list,
358                                                                 aff_list) {
359                 if (&ctx->aff_list == &gang->aff_list_head)
360                         break;
361                 lowest_offset = ctx->aff_offset;
362         }
363 
364         gang->aff_ref_spu = aff_ref_location(gang->aff_ref_ctx, mem_aff, gs,
365                                                         lowest_offset);
366 }
367 
368 static struct spu *ctx_location(struct spu *ref, int offset, int node)
369 {
370         struct spu *spu;
371 
372         spu = NULL;
373         if (offset >= 0) {
374                 list_for_each_entry(spu, ref->aff_list.prev, aff_list) {
375                         BUG_ON(spu->node != node);
376                         if (offset == 0)
377                                 break;
378                         if (sched_spu(spu))
379                                 offset--;
380                 }
381         } else {
382                 list_for_each_entry_reverse(spu, ref->aff_list.next, aff_list) {
383                         BUG_ON(spu->node != node);
384                         if (offset == 0)
385                                 break;
386                         if (sched_spu(spu))
387                                 offset++;
388                 }
389         }
390 
391         return spu;
392 }
393 
394 /*
395  * affinity_check is called each time a context is going to be scheduled.
396  * It returns the spu ptr on which the context must run.
397  */
398 static int has_affinity(struct spu_context *ctx)
399 {
400         struct spu_gang *gang = ctx->gang;
401 
402         if (list_empty(&ctx->aff_list))
403                 return 0;
404 
405         if (atomic_read(&ctx->gang->aff_sched_count) == 0)
406                 ctx->gang->aff_ref_spu = NULL;
407 
408         if (!gang->aff_ref_spu) {
409                 if (!(gang->aff_flags & AFF_MERGED))
410                         aff_merge_remaining_ctxs(gang);
411                 if (!(gang->aff_flags & AFF_OFFSETS_SET))
412                         aff_set_offsets(gang);
413                 aff_set_ref_point_location(gang);
414         }
415 
416         return gang->aff_ref_spu != NULL;
417 }
418 
419 /**
420  * spu_unbind_context - unbind spu context from physical spu
421  * @spu:        physical spu to unbind from
422  * @ctx:        context to unbind
423  */
424 static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
425 {
426         u32 status;
427 
428         spu_context_trace(spu_unbind_context__enter, ctx, spu);
429 
430         spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
431 
432         if (spu->ctx->flags & SPU_CREATE_NOSCHED)
433                 atomic_dec(&cbe_spu_info[spu->node].reserved_spus);
434 
435         if (ctx->gang)
436                 /*
437                  * If ctx->gang->aff_sched_count is positive, SPU affinity is
438                  * being considered in this gang. Using atomic_dec_if_positive
439                  * allow us to skip an explicit check for affinity in this gang
440                  */
441                 atomic_dec_if_positive(&ctx->gang->aff_sched_count);
442 
443         spu_switch_notify(spu, NULL);
444         spu_unmap_mappings(ctx);
445         spu_save(&ctx->csa, spu);
446         spu_switch_log_notify(spu, ctx, SWITCH_LOG_STOP, 0);
447 
448         spin_lock_irq(&spu->register_lock);
449         spu->timestamp = jiffies;
450         ctx->state = SPU_STATE_SAVED;
451         spu->ibox_callback = NULL;
452         spu->wbox_callback = NULL;
453         spu->stop_callback = NULL;
454         spu->mfc_callback = NULL;
455         spu->pid = 0;
456         spu->tgid = 0;
457         ctx->ops = &spu_backing_ops;
458         spu->flags = 0;
459         spu->ctx = NULL;
460         spin_unlock_irq(&spu->register_lock);
461 
462         spu_associate_mm(spu, NULL);
463 
464         ctx->stats.slb_flt +=
465                 (spu->stats.slb_flt - ctx->stats.slb_flt_base);
466         ctx->stats.class2_intr +=
467                 (spu->stats.class2_intr - ctx->stats.class2_intr_base);
468 
469         /* This maps the underlying spu state to idle */
470         spuctx_switch_state(ctx, SPU_UTIL_IDLE_LOADED);
471         ctx->spu = NULL;
472 
473         if (spu_stopped(ctx, &status))
474                 wake_up_all(&ctx->stop_wq);
475 }
476 
477 /**
478  * spu_add_to_rq - add a context to the runqueue
479  * @ctx:       context to add
480  */
481 static void __spu_add_to_rq(struct spu_context *ctx)
482 {
483         /*
484          * Unfortunately this code path can be called from multiple threads
485          * on behalf of a single context due to the way the problem state
486          * mmap support works.
487          *
488          * Fortunately we need to wake up all these threads at the same time
489          * and can simply skip the runqueue addition for every but the first
490          * thread getting into this codepath.
491          *
492          * It's still quite hacky, and long-term we should proxy all other
493          * threads through the owner thread so that spu_run is in control
494          * of all the scheduling activity for a given context.
495          */
496         if (list_empty(&ctx->rq)) {
497                 list_add_tail(&ctx->rq, &spu_prio->runq[ctx->prio]);
498                 set_bit(ctx->prio, spu_prio->bitmap);
499                 if (!spu_prio->nr_waiting++)
500                         mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
501         }
502 }
503 
504 static void spu_add_to_rq(struct spu_context *ctx)
505 {
506         spin_lock(&spu_prio->runq_lock);
507         __spu_add_to_rq(ctx);
508         spin_unlock(&spu_prio->runq_lock);
509 }
510 
511 static void __spu_del_from_rq(struct spu_context *ctx)
512 {
513         int prio = ctx->prio;
514 
515         if (!list_empty(&ctx->rq)) {
516                 if (!--spu_prio->nr_waiting)
517                         del_timer(&spusched_timer);
518                 list_del_init(&ctx->rq);
519 
520                 if (list_empty(&spu_prio->runq[prio]))
521                         clear_bit(prio, spu_prio->bitmap);
522         }
523 }
524 
525 void spu_del_from_rq(struct spu_context *ctx)
526 {
527         spin_lock(&spu_prio->runq_lock);
528         __spu_del_from_rq(ctx);
529         spin_unlock(&spu_prio->runq_lock);
530 }
531 
532 static void spu_prio_wait(struct spu_context *ctx)
533 {
534         DEFINE_WAIT(wait);
535 
536         /*
537          * The caller must explicitly wait for a context to be loaded
538          * if the nosched flag is set.  If NOSCHED is not set, the caller
539          * queues the context and waits for an spu event or error.
540          */
541         BUG_ON(!(ctx->flags & SPU_CREATE_NOSCHED));
542 
543         spin_lock(&spu_prio->runq_lock);
544         prepare_to_wait_exclusive(&ctx->stop_wq, &wait, TASK_INTERRUPTIBLE);
545         if (!signal_pending(current)) {
546                 __spu_add_to_rq(ctx);
547                 spin_unlock(&spu_prio->runq_lock);
548                 mutex_unlock(&ctx->state_mutex);
549                 schedule();
550                 mutex_lock(&ctx->state_mutex);
551                 spin_lock(&spu_prio->runq_lock);
552                 __spu_del_from_rq(ctx);
553         }
554         spin_unlock(&spu_prio->runq_lock);
555         __set_current_state(TASK_RUNNING);
556         remove_wait_queue(&ctx->stop_wq, &wait);
557 }
558 
559 static struct spu *spu_get_idle(struct spu_context *ctx)
560 {
561         struct spu *spu, *aff_ref_spu;
562         int node, n;
563 
564         spu_context_nospu_trace(spu_get_idle__enter, ctx);
565 
566         if (ctx->gang) {
567                 mutex_lock(&ctx->gang->aff_mutex);
568                 if (has_affinity(ctx)) {
569                         aff_ref_spu = ctx->gang->aff_ref_spu;
570                         atomic_inc(&ctx->gang->aff_sched_count);
571                         mutex_unlock(&ctx->gang->aff_mutex);
572                         node = aff_ref_spu->node;
573 
574                         mutex_lock(&cbe_spu_info[node].list_mutex);
575                         spu = ctx_location(aff_ref_spu, ctx->aff_offset, node);
576                         if (spu && spu->alloc_state == SPU_FREE)
577                                 goto found;
578                         mutex_unlock(&cbe_spu_info[node].list_mutex);
579 
580                         atomic_dec(&ctx->gang->aff_sched_count);
581                         goto not_found;
582                 }
583                 mutex_unlock(&ctx->gang->aff_mutex);
584         }
585         node = cpu_to_node(raw_smp_processor_id());
586         for (n = 0; n < MAX_NUMNODES; n++, node++) {
587                 node = (node < MAX_NUMNODES) ? node : 0;
588                 if (!node_allowed(ctx, node))
589                         continue;
590 
591                 mutex_lock(&cbe_spu_info[node].list_mutex);
592                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
593                         if (spu->alloc_state == SPU_FREE)
594                                 goto found;
595                 }
596                 mutex_unlock(&cbe_spu_info[node].list_mutex);
597         }
598 
599  not_found:
600         spu_context_nospu_trace(spu_get_idle__not_found, ctx);
601         return NULL;
602 
603  found:
604         spu->alloc_state = SPU_USED;
605         mutex_unlock(&cbe_spu_info[node].list_mutex);
606         spu_context_trace(spu_get_idle__found, ctx, spu);
607         spu_init_channels(spu);
608         return spu;
609 }
610 
611 /**
612  * find_victim - find a lower priority context to preempt
613  * @ctx:        candidate context for running
614  *
615  * Returns the freed physical spu to run the new context on.
616  */
617 static struct spu *find_victim(struct spu_context *ctx)
618 {
619         struct spu_context *victim = NULL;
620         struct spu *spu;
621         int node, n;
622 
623         spu_context_nospu_trace(spu_find_victim__enter, ctx);
624 
625         /*
626          * Look for a possible preemption candidate on the local node first.
627          * If there is no candidate look at the other nodes.  This isn't
628          * exactly fair, but so far the whole spu scheduler tries to keep
629          * a strong node affinity.  We might want to fine-tune this in
630          * the future.
631          */
632  restart:
633         node = cpu_to_node(raw_smp_processor_id());
634         for (n = 0; n < MAX_NUMNODES; n++, node++) {
635                 node = (node < MAX_NUMNODES) ? node : 0;
636                 if (!node_allowed(ctx, node))
637                         continue;
638 
639                 mutex_lock(&cbe_spu_info[node].list_mutex);
640                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
641                         struct spu_context *tmp = spu->ctx;
642 
643                         if (tmp && tmp->prio > ctx->prio &&
644                             !(tmp->flags & SPU_CREATE_NOSCHED) &&
645                             (!victim || tmp->prio > victim->prio)) {
646                                 victim = spu->ctx;
647                         }
648                 }
649                 if (victim)
650                         get_spu_context(victim);
651                 mutex_unlock(&cbe_spu_info[node].list_mutex);
652 
653                 if (victim) {
654                         /*
655                          * This nests ctx->state_mutex, but we always lock
656                          * higher priority contexts before lower priority
657                          * ones, so this is safe until we introduce
658                          * priority inheritance schemes.
659                          *
660                          * XXX if the highest priority context is locked,
661                          * this can loop a long time.  Might be better to
662                          * look at another context or give up after X retries.
663                          */
664                         if (!mutex_trylock(&victim->state_mutex)) {
665                                 put_spu_context(victim);
666                                 victim = NULL;
667                                 goto restart;
668                         }
669 
670                         spu = victim->spu;
671                         if (!spu || victim->prio <= ctx->prio) {
672                                 /*
673                                  * This race can happen because we've dropped
674                                  * the active list mutex.  Not a problem, just
675                                  * restart the search.
676                                  */
677                                 mutex_unlock(&victim->state_mutex);
678                                 put_spu_context(victim);
679                                 victim = NULL;
680                                 goto restart;
681                         }
682 
683                         spu_context_trace(__spu_deactivate__unload, ctx, spu);
684 
685                         mutex_lock(&cbe_spu_info[node].list_mutex);
686                         cbe_spu_info[node].nr_active--;
687                         spu_unbind_context(spu, victim);
688                         mutex_unlock(&cbe_spu_info[node].list_mutex);
689 
690                         victim->stats.invol_ctx_switch++;
691                         spu->stats.invol_ctx_switch++;
692                         if (test_bit(SPU_SCHED_SPU_RUN, &victim->sched_flags))
693                                 spu_add_to_rq(victim);
694 
695                         mutex_unlock(&victim->state_mutex);
696                         put_spu_context(victim);
697 
698                         return spu;
699                 }
700         }
701 
702         return NULL;
703 }
704 
705 static void __spu_schedule(struct spu *spu, struct spu_context *ctx)
706 {
707         int node = spu->node;
708         int success = 0;
709 
710         spu_set_timeslice(ctx);
711 
712         mutex_lock(&cbe_spu_info[node].list_mutex);
713         if (spu->ctx == NULL) {
714                 spu_bind_context(spu, ctx);
715                 cbe_spu_info[node].nr_active++;
716                 spu->alloc_state = SPU_USED;
717                 success = 1;
718         }
719         mutex_unlock(&cbe_spu_info[node].list_mutex);
720 
721         if (success)
722                 wake_up_all(&ctx->run_wq);
723         else
724                 spu_add_to_rq(ctx);
725 }
726 
727 static void spu_schedule(struct spu *spu, struct spu_context *ctx)
728 {
729         /* not a candidate for interruptible because it's called either
730            from the scheduler thread or from spu_deactivate */
731         mutex_lock(&ctx->state_mutex);
732         if (ctx->state == SPU_STATE_SAVED)
733                 __spu_schedule(spu, ctx);
734         spu_release(ctx);
735 }
736 
737 /**
738  * spu_unschedule - remove a context from a spu, and possibly release it.
739  * @spu:        The SPU to unschedule from
740  * @ctx:        The context currently scheduled on the SPU
741  * @free_spu    Whether to free the SPU for other contexts
742  *
743  * Unbinds the context @ctx from the SPU @spu. If @free_spu is non-zero, the
744  * SPU is made available for other contexts (ie, may be returned by
745  * spu_get_idle). If this is zero, the caller is expected to schedule another
746  * context to this spu.
747  *
748  * Should be called with ctx->state_mutex held.
749  */
750 static void spu_unschedule(struct spu *spu, struct spu_context *ctx,
751                 int free_spu)
752 {
753         int node = spu->node;
754 
755         mutex_lock(&cbe_spu_info[node].list_mutex);
756         cbe_spu_info[node].nr_active--;
757         if (free_spu)
758                 spu->alloc_state = SPU_FREE;
759         spu_unbind_context(spu, ctx);
760         ctx->stats.invol_ctx_switch++;
761         spu->stats.invol_ctx_switch++;
762         mutex_unlock(&cbe_spu_info[node].list_mutex);
763 }
764 
765 /**
766  * spu_activate - find a free spu for a context and execute it
767  * @ctx:        spu context to schedule
768  * @flags:      flags (currently ignored)
769  *
770  * Tries to find a free spu to run @ctx.  If no free spu is available
771  * add the context to the runqueue so it gets woken up once an spu
772  * is available.
773  */
774 int spu_activate(struct spu_context *ctx, unsigned long flags)
775 {
776         struct spu *spu;
777 
778         /*
779          * If there are multiple threads waiting for a single context
780          * only one actually binds the context while the others will
781          * only be able to acquire the state_mutex once the context
782          * already is in runnable state.
783          */
784         if (ctx->spu)
785                 return 0;
786 
787 spu_activate_top:
788         if (signal_pending(current))
789                 return -ERESTARTSYS;
790 
791         spu = spu_get_idle(ctx);
792         /*
793          * If this is a realtime thread we try to get it running by
794          * preempting a lower priority thread.
795          */
796         if (!spu && rt_prio(ctx->prio))
797                 spu = find_victim(ctx);
798         if (spu) {
799                 unsigned long runcntl;
800 
801                 runcntl = ctx->ops->runcntl_read(ctx);
802                 __spu_schedule(spu, ctx);
803                 if (runcntl & SPU_RUNCNTL_RUNNABLE)
804                         spuctx_switch_state(ctx, SPU_UTIL_USER);
805 
806                 return 0;
807         }
808 
809         if (ctx->flags & SPU_CREATE_NOSCHED) {
810                 spu_prio_wait(ctx);
811                 goto spu_activate_top;
812         }
813 
814         spu_add_to_rq(ctx);
815 
816         return 0;
817 }
818 
819 /**
820  * grab_runnable_context - try to find a runnable context
821  *
822  * Remove the highest priority context on the runqueue and return it
823  * to the caller.  Returns %NULL if no runnable context was found.
824  */
825 static struct spu_context *grab_runnable_context(int prio, int node)
826 {
827         struct spu_context *ctx;
828         int best;
829 
830         spin_lock(&spu_prio->runq_lock);
831         best = find_first_bit(spu_prio->bitmap, prio);
832         while (best < prio) {
833                 struct list_head *rq = &spu_prio->runq[best];
834 
835                 list_for_each_entry(ctx, rq, rq) {
836                         /* XXX(hch): check for affinity here as well */
837                         if (__node_allowed(ctx, node)) {
838                                 __spu_del_from_rq(ctx);
839                                 goto found;
840                         }
841                 }
842                 best++;
843         }
844         ctx = NULL;
845  found:
846         spin_unlock(&spu_prio->runq_lock);
847         return ctx;
848 }
849 
850 static int __spu_deactivate(struct spu_context *ctx, int force, int max_prio)
851 {
852         struct spu *spu = ctx->spu;
853         struct spu_context *new = NULL;
854 
855         if (spu) {
856                 new = grab_runnable_context(max_prio, spu->node);
857                 if (new || force) {
858                         spu_unschedule(spu, ctx, new == NULL);
859                         if (new) {
860                                 if (new->flags & SPU_CREATE_NOSCHED)
861                                         wake_up(&new->stop_wq);
862                                 else {
863                                         spu_release(ctx);
864                                         spu_schedule(spu, new);
865                                         /* this one can't easily be made
866                                            interruptible */
867                                         mutex_lock(&ctx->state_mutex);
868                                 }
869                         }
870                 }
871         }
872 
873         return new != NULL;
874 }
875 
876 /**
877  * spu_deactivate - unbind a context from it's physical spu
878  * @ctx:        spu context to unbind
879  *
880  * Unbind @ctx from the physical spu it is running on and schedule
881  * the highest priority context to run on the freed physical spu.
882  */
883 void spu_deactivate(struct spu_context *ctx)
884 {
885         spu_context_nospu_trace(spu_deactivate__enter, ctx);
886         __spu_deactivate(ctx, 1, MAX_PRIO);
887 }
888 
889 /**
890  * spu_yield -  yield a physical spu if others are waiting
891  * @ctx:        spu context to yield
892  *
893  * Check if there is a higher priority context waiting and if yes
894  * unbind @ctx from the physical spu and schedule the highest
895  * priority context to run on the freed physical spu instead.
896  */
897 void spu_yield(struct spu_context *ctx)
898 {
899         spu_context_nospu_trace(spu_yield__enter, ctx);
900         if (!(ctx->flags & SPU_CREATE_NOSCHED)) {
901                 mutex_lock(&ctx->state_mutex);
902                 __spu_deactivate(ctx, 0, MAX_PRIO);
903                 mutex_unlock(&ctx->state_mutex);
904         }
905 }
906 
907 static noinline void spusched_tick(struct spu_context *ctx)
908 {
909         struct spu_context *new = NULL;
910         struct spu *spu = NULL;
911 
912         if (spu_acquire(ctx))
913                 BUG();  /* a kernel thread never has signals pending */
914 
915         if (ctx->state != SPU_STATE_RUNNABLE)
916                 goto out;
917         if (ctx->flags & SPU_CREATE_NOSCHED)
918                 goto out;
919         if (ctx->policy == SCHED_FIFO)
920                 goto out;
921 
922         if (--ctx->time_slice && test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
923                 goto out;
924 
925         spu = ctx->spu;
926 
927         spu_context_trace(spusched_tick__preempt, ctx, spu);
928 
929         new = grab_runnable_context(ctx->prio + 1, spu->node);
930         if (new) {
931                 spu_unschedule(spu, ctx, 0);
932                 if (test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
933                         spu_add_to_rq(ctx);
934         } else {
935                 spu_context_nospu_trace(spusched_tick__newslice, ctx);
936                 if (!ctx->time_slice)
937                         ctx->time_slice++;
938         }
939 out:
940         spu_release(ctx);
941 
942         if (new)
943                 spu_schedule(spu, new);
944 }
945 
946 /**
947  * count_active_contexts - count nr of active tasks
948  *
949  * Return the number of tasks currently running or waiting to run.
950  *
951  * Note that we don't take runq_lock / list_mutex here.  Reading
952  * a single 32bit value is atomic on powerpc, and we don't care
953  * about memory ordering issues here.
954  */
955 static unsigned long count_active_contexts(void)
956 {
957         int nr_active = 0, node;
958 
959         for (node = 0; node < MAX_NUMNODES; node++)
960                 nr_active += cbe_spu_info[node].nr_active;
961         nr_active += spu_prio->nr_waiting;
962 
963         return nr_active;
964 }
965 
966 /**
967  * spu_calc_load - update the avenrun load estimates.
968  *
969  * No locking against reading these values from userspace, as for
970  * the CPU loadavg code.
971  */
972 static void spu_calc_load(void)
973 {
974         unsigned long active_tasks; /* fixed-point */
975 
976         active_tasks = count_active_contexts() * FIXED_1;
977         spu_avenrun[0] = calc_load(spu_avenrun[0], EXP_1, active_tasks);
978         spu_avenrun[1] = calc_load(spu_avenrun[1], EXP_5, active_tasks);
979         spu_avenrun[2] = calc_load(spu_avenrun[2], EXP_15, active_tasks);
980 }
981 
982 static void spusched_wake(struct timer_list *unused)
983 {
984         mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
985         wake_up_process(spusched_task);
986 }
987 
988 static void spuloadavg_wake(struct timer_list *unused)
989 {
990         mod_timer(&spuloadavg_timer, jiffies + LOAD_FREQ);
991         spu_calc_load();
992 }
993 
994 static int spusched_thread(void *unused)
995 {
996         struct spu *spu;
997         int node;
998 
999         while (!kthread_should_stop()) {
1000                 set_current_state(TASK_INTERRUPTIBLE);
1001                 schedule();
1002                 for (node = 0; node < MAX_NUMNODES; node++) {
1003                         struct mutex *mtx = &cbe_spu_info[node].list_mutex;
1004 
1005                         mutex_lock(mtx);
1006                         list_for_each_entry(spu, &cbe_spu_info[node].spus,
1007                                         cbe_list) {
1008                                 struct spu_context *ctx = spu->ctx;
1009 
1010                                 if (ctx) {
1011                                         get_spu_context(ctx);
1012                                         mutex_unlock(mtx);
1013                                         spusched_tick(ctx);
1014                                         mutex_lock(mtx);
1015                                         put_spu_context(ctx);
1016                                 }
1017                         }
1018                         mutex_unlock(mtx);
1019                 }
1020         }
1021 
1022         return 0;
1023 }
1024 
1025 void spuctx_switch_state(struct spu_context *ctx,
1026                 enum spu_utilization_state new_state)
1027 {
1028         unsigned long long curtime;
1029         signed long long delta;
1030         struct spu *spu;
1031         enum spu_utilization_state old_state;
1032         int node;
1033 
1034         curtime = ktime_get_ns();
1035         delta = curtime - ctx->stats.tstamp;
1036 
1037         WARN_ON(!mutex_is_locked(&ctx->state_mutex));
1038         WARN_ON(delta < 0);
1039 
1040         spu = ctx->spu;
1041         old_state = ctx->stats.util_state;
1042         ctx->stats.util_state = new_state;
1043         ctx->stats.tstamp = curtime;
1044 
1045         /*
1046          * Update the physical SPU utilization statistics.
1047          */
1048         if (spu) {
1049                 ctx->stats.times[old_state] += delta;
1050                 spu->stats.times[old_state] += delta;
1051                 spu->stats.util_state = new_state;
1052                 spu->stats.tstamp = curtime;
1053                 node = spu->node;
1054                 if (old_state == SPU_UTIL_USER)
1055                         atomic_dec(&cbe_spu_info[node].busy_spus);
1056                 if (new_state == SPU_UTIL_USER)
1057                         atomic_inc(&cbe_spu_info[node].busy_spus);
1058         }
1059 }
1060 
1061 static int show_spu_loadavg(struct seq_file *s, void *private)
1062 {
1063         int a, b, c;
1064 
1065         a = spu_avenrun[0] + (FIXED_1/200);
1066         b = spu_avenrun[1] + (FIXED_1/200);
1067         c = spu_avenrun[2] + (FIXED_1/200);
1068 
1069         /*
1070          * Note that last_pid doesn't really make much sense for the
1071          * SPU loadavg (it even seems very odd on the CPU side...),
1072          * but we include it here to have a 100% compatible interface.
1073          */
1074         seq_printf(s, "%d.%02d %d.%02d %d.%02d %ld/%d %d\n",
1075                 LOAD_INT(a), LOAD_FRAC(a),
1076                 LOAD_INT(b), LOAD_FRAC(b),
1077                 LOAD_INT(c), LOAD_FRAC(c),
1078                 count_active_contexts(),
1079                 atomic_read(&nr_spu_contexts),
1080                 idr_get_cursor(&task_active_pid_ns(current)->idr) - 1);
1081         return 0;
1082 };
1083 
1084 int __init spu_sched_init(void)
1085 {
1086         struct proc_dir_entry *entry;
1087         int err = -ENOMEM, i;
1088 
1089         spu_prio = kzalloc(sizeof(struct spu_prio_array), GFP_KERNEL);
1090         if (!spu_prio)
1091                 goto out;
1092 
1093         for (i = 0; i < MAX_PRIO; i++) {
1094                 INIT_LIST_HEAD(&spu_prio->runq[i]);
1095                 __clear_bit(i, spu_prio->bitmap);
1096         }
1097         spin_lock_init(&spu_prio->runq_lock);
1098 
1099         timer_setup(&spusched_timer, spusched_wake, 0);
1100         timer_setup(&spuloadavg_timer, spuloadavg_wake, 0);
1101 
1102         spusched_task = kthread_run(spusched_thread, NULL, "spusched");
1103         if (IS_ERR(spusched_task)) {
1104                 err = PTR_ERR(spusched_task);
1105                 goto out_free_spu_prio;
1106         }
1107 
1108         mod_timer(&spuloadavg_timer, 0);
1109 
1110         entry = proc_create_single("spu_loadavg", 0, NULL, show_spu_loadavg);
1111         if (!entry)
1112                 goto out_stop_kthread;
1113 
1114         pr_debug("spusched: tick: %d, min ticks: %d, default ticks: %d\n",
1115                         SPUSCHED_TICK, MIN_SPU_TIMESLICE, DEF_SPU_TIMESLICE);
1116         return 0;
1117 
1118  out_stop_kthread:
1119         kthread_stop(spusched_task);
1120  out_free_spu_prio:
1121         kfree(spu_prio);
1122  out:
1123         return err;
1124 }
1125 
1126 void spu_sched_exit(void)
1127 {
1128         struct spu *spu;
1129         int node;
1130 
1131         remove_proc_entry("spu_loadavg", NULL);
1132 
1133         del_timer_sync(&spusched_timer);
1134         del_timer_sync(&spuloadavg_timer);
1135         kthread_stop(spusched_task);
1136 
1137         for (node = 0; node < MAX_NUMNODES; node++) {
1138                 mutex_lock(&cbe_spu_info[node].list_mutex);
1139                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list)
1140                         if (spu->alloc_state != SPU_FREE)
1141                                 spu->alloc_state = SPU_FREE;
1142                 mutex_unlock(&cbe_spu_info[node].list_mutex);
1143         }
1144         kfree(spu_prio);
1145 }
1146 

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