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

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  1 /* sched.c - SPU scheduler.
  2  *
  3  * Copyright (C) IBM 2005
  4  * Author: Mark Nutter <mnutter@us.ibm.com>
  5  *
  6  * 2006-03-31   NUMA domains added.
  7  *
  8  * This program is free software; you can redistribute it and/or modify
  9  * it under the terms of the GNU General Public License as published by
 10  * the Free Software Foundation; either version 2, or (at your option)
 11  * any later version.
 12  *
 13  * This program is distributed in the hope that it will be useful,
 14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 16  * GNU General Public License for more details.
 17  *
 18  * You should have received a copy of the GNU General Public License
 19  * along with this program; if not, write to the Free Software
 20  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 21  */
 22 
 23 #undef DEBUG
 24 
 25 #include <linux/errno.h>
 26 #include <linux/sched.h>
 27 #include <linux/sched/rt.h>
 28 #include <linux/kernel.h>
 29 #include <linux/mm.h>
 30 #include <linux/slab.h>
 31 #include <linux/completion.h>
 32 #include <linux/vmalloc.h>
 33 #include <linux/smp.h>
 34 #include <linux/stddef.h>
 35 #include <linux/unistd.h>
 36 #include <linux/numa.h>
 37 #include <linux/mutex.h>
 38 #include <linux/notifier.h>
 39 #include <linux/kthread.h>
 40 #include <linux/pid_namespace.h>
 41 #include <linux/proc_fs.h>
 42 #include <linux/seq_file.h>
 43 
 44 #include <asm/io.h>
 45 #include <asm/mmu_context.h>
 46 #include <asm/spu.h>
 47 #include <asm/spu_csa.h>
 48 #include <asm/spu_priv1.h>
 49 #include "spufs.h"
 50 #define CREATE_TRACE_POINTS
 51 #include "sputrace.h"
 52 
 53 struct spu_prio_array {
 54         DECLARE_BITMAP(bitmap, MAX_PRIO);
 55         struct list_head runq[MAX_PRIO];
 56         spinlock_t runq_lock;
 57         int nr_waiting;
 58 };
 59 
 60 static unsigned long spu_avenrun[3];
 61 static struct spu_prio_array *spu_prio;
 62 static struct task_struct *spusched_task;
 63 static struct timer_list spusched_timer;
 64 static struct timer_list spuloadavg_timer;
 65 
 66 /*
 67  * Priority of a normal, non-rt, non-niced'd process (aka nice level 0).
 68  */
 69 #define NORMAL_PRIO             120
 70 
 71 /*
 72  * Frequency of the spu scheduler tick.  By default we do one SPU scheduler
 73  * tick for every 10 CPU scheduler ticks.
 74  */
 75 #define SPUSCHED_TICK           (10)
 76 
 77 /*
 78  * These are the 'tuning knobs' of the scheduler:
 79  *
 80  * Minimum timeslice is 5 msecs (or 1 spu scheduler tick, whichever is
 81  * larger), default timeslice is 100 msecs, maximum timeslice is 800 msecs.
 82  */
 83 #define MIN_SPU_TIMESLICE       max(5 * HZ / (1000 * SPUSCHED_TICK), 1)
 84 #define DEF_SPU_TIMESLICE       (100 * HZ / (1000 * SPUSCHED_TICK))
 85 
 86 #define SCALE_PRIO(x, prio) \
 87         max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_SPU_TIMESLICE)
 88 
 89 /*
 90  * scale user-nice values [ -20 ... 0 ... 19 ] to time slice values:
 91  * [800ms ... 100ms ... 5ms]
 92  *
 93  * The higher a thread's priority, the bigger timeslices
 94  * it gets during one round of execution. But even the lowest
 95  * priority thread gets MIN_TIMESLICE worth of execution time.
 96  */
 97 void spu_set_timeslice(struct spu_context *ctx)
 98 {
 99         if (ctx->prio < NORMAL_PRIO)
100                 ctx->time_slice = SCALE_PRIO(DEF_SPU_TIMESLICE * 4, ctx->prio);
101         else
102                 ctx->time_slice = SCALE_PRIO(DEF_SPU_TIMESLICE, ctx->prio);
103 }
104 
105 /*
106  * Update scheduling information from the owning thread.
107  */
108 void __spu_update_sched_info(struct spu_context *ctx)
109 {
110         /*
111          * assert that the context is not on the runqueue, so it is safe
112          * to change its scheduling parameters.
113          */
114         BUG_ON(!list_empty(&ctx->rq));
115 
116         /*
117          * 32-Bit assignments are atomic on powerpc, and we don't care about
118          * memory ordering here because retrieving the controlling thread is
119          * per definition racy.
120          */
121         ctx->tid = current->pid;
122 
123         /*
124          * We do our own priority calculations, so we normally want
125          * ->static_prio to start with. Unfortunately this field
126          * contains junk for threads with a realtime scheduling
127          * policy so we have to look at ->prio in this case.
128          */
129         if (rt_prio(current->prio))
130                 ctx->prio = current->prio;
131         else
132                 ctx->prio = current->static_prio;
133         ctx->policy = current->policy;
134 
135         /*
136          * TO DO: the context may be loaded, so we may need to activate
137          * it again on a different node. But it shouldn't hurt anything
138          * to update its parameters, because we know that the scheduler
139          * is not actively looking at this field, since it is not on the
140          * runqueue. The context will be rescheduled on the proper node
141          * if it is timesliced or preempted.
142          */
143         cpumask_copy(&ctx->cpus_allowed, tsk_cpus_allowed(current));
144 
145         /* Save the current cpu id for spu interrupt routing. */
146         ctx->last_ran = raw_smp_processor_id();
147 }
148 
149 void spu_update_sched_info(struct spu_context *ctx)
150 {
151         int node;
152 
153         if (ctx->state == SPU_STATE_RUNNABLE) {
154                 node = ctx->spu->node;
155 
156                 /*
157                  * Take list_mutex to sync with find_victim().
158                  */
159                 mutex_lock(&cbe_spu_info[node].list_mutex);
160                 __spu_update_sched_info(ctx);
161                 mutex_unlock(&cbe_spu_info[node].list_mutex);
162         } else {
163                 __spu_update_sched_info(ctx);
164         }
165 }
166 
167 static int __node_allowed(struct spu_context *ctx, int node)
168 {
169         if (nr_cpus_node(node)) {
170                 const struct cpumask *mask = cpumask_of_node(node);
171 
172                 if (cpumask_intersects(mask, &ctx->cpus_allowed))
173                         return 1;
174         }
175 
176         return 0;
177 }
178 
179 static int node_allowed(struct spu_context *ctx, int node)
180 {
181         int rval;
182 
183         spin_lock(&spu_prio->runq_lock);
184         rval = __node_allowed(ctx, node);
185         spin_unlock(&spu_prio->runq_lock);
186 
187         return rval;
188 }
189 
190 void do_notify_spus_active(void)
191 {
192         int node;
193 
194         /*
195          * Wake up the active spu_contexts.
196          *
197          * When the awakened processes see their "notify_active" flag is set,
198          * they will call spu_switch_notify().
199          */
200         for_each_online_node(node) {
201                 struct spu *spu;
202 
203                 mutex_lock(&cbe_spu_info[node].list_mutex);
204                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
205                         if (spu->alloc_state != SPU_FREE) {
206                                 struct spu_context *ctx = spu->ctx;
207                                 set_bit(SPU_SCHED_NOTIFY_ACTIVE,
208                                         &ctx->sched_flags);
209                                 mb();
210                                 wake_up_all(&ctx->stop_wq);
211                         }
212                 }
213                 mutex_unlock(&cbe_spu_info[node].list_mutex);
214         }
215 }
216 
217 /**
218  * spu_bind_context - bind spu context to physical spu
219  * @spu:        physical spu to bind to
220  * @ctx:        context to bind
221  */
222 static void spu_bind_context(struct spu *spu, struct spu_context *ctx)
223 {
224         spu_context_trace(spu_bind_context__enter, ctx, spu);
225 
226         spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
227 
228         if (ctx->flags & SPU_CREATE_NOSCHED)
229                 atomic_inc(&cbe_spu_info[spu->node].reserved_spus);
230 
231         ctx->stats.slb_flt_base = spu->stats.slb_flt;
232         ctx->stats.class2_intr_base = spu->stats.class2_intr;
233 
234         spu_associate_mm(spu, ctx->owner);
235 
236         spin_lock_irq(&spu->register_lock);
237         spu->ctx = ctx;
238         spu->flags = 0;
239         ctx->spu = spu;
240         ctx->ops = &spu_hw_ops;
241         spu->pid = current->pid;
242         spu->tgid = current->tgid;
243         spu->ibox_callback = spufs_ibox_callback;
244         spu->wbox_callback = spufs_wbox_callback;
245         spu->stop_callback = spufs_stop_callback;
246         spu->mfc_callback = spufs_mfc_callback;
247         spin_unlock_irq(&spu->register_lock);
248 
249         spu_unmap_mappings(ctx);
250 
251         spu_switch_log_notify(spu, ctx, SWITCH_LOG_START, 0);
252         spu_restore(&ctx->csa, spu);
253         spu->timestamp = jiffies;
254         spu_switch_notify(spu, ctx);
255         ctx->state = SPU_STATE_RUNNABLE;
256 
257         spuctx_switch_state(ctx, SPU_UTIL_USER);
258 }
259 
260 /*
261  * Must be used with the list_mutex held.
262  */
263 static inline int sched_spu(struct spu *spu)
264 {
265         BUG_ON(!mutex_is_locked(&cbe_spu_info[spu->node].list_mutex));
266 
267         return (!spu->ctx || !(spu->ctx->flags & SPU_CREATE_NOSCHED));
268 }
269 
270 static void aff_merge_remaining_ctxs(struct spu_gang *gang)
271 {
272         struct spu_context *ctx;
273 
274         list_for_each_entry(ctx, &gang->aff_list_head, aff_list) {
275                 if (list_empty(&ctx->aff_list))
276                         list_add(&ctx->aff_list, &gang->aff_list_head);
277         }
278         gang->aff_flags |= AFF_MERGED;
279 }
280 
281 static void aff_set_offsets(struct spu_gang *gang)
282 {
283         struct spu_context *ctx;
284         int offset;
285 
286         offset = -1;
287         list_for_each_entry_reverse(ctx, &gang->aff_ref_ctx->aff_list,
288                                                                 aff_list) {
289                 if (&ctx->aff_list == &gang->aff_list_head)
290                         break;
291                 ctx->aff_offset = offset--;
292         }
293 
294         offset = 0;
295         list_for_each_entry(ctx, gang->aff_ref_ctx->aff_list.prev, aff_list) {
296                 if (&ctx->aff_list == &gang->aff_list_head)
297                         break;
298                 ctx->aff_offset = offset++;
299         }
300 
301         gang->aff_flags |= AFF_OFFSETS_SET;
302 }
303 
304 static struct spu *aff_ref_location(struct spu_context *ctx, int mem_aff,
305                  int group_size, int lowest_offset)
306 {
307         struct spu *spu;
308         int node, n;
309 
310         /*
311          * TODO: A better algorithm could be used to find a good spu to be
312          *       used as reference location for the ctxs chain.
313          */
314         node = cpu_to_node(raw_smp_processor_id());
315         for (n = 0; n < MAX_NUMNODES; n++, node++) {
316                 /*
317                  * "available_spus" counts how many spus are not potentially
318                  * going to be used by other affinity gangs whose reference
319                  * context is already in place. Although this code seeks to
320                  * avoid having affinity gangs with a summed amount of
321                  * contexts bigger than the amount of spus in the node,
322                  * this may happen sporadically. In this case, available_spus
323                  * becomes negative, which is harmless.
324                  */
325                 int available_spus;
326 
327                 node = (node < MAX_NUMNODES) ? node : 0;
328                 if (!node_allowed(ctx, node))
329                         continue;
330 
331                 available_spus = 0;
332                 mutex_lock(&cbe_spu_info[node].list_mutex);
333                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
334                         if (spu->ctx && spu->ctx->gang && !spu->ctx->aff_offset
335                                         && spu->ctx->gang->aff_ref_spu)
336                                 available_spus -= spu->ctx->gang->contexts;
337                         available_spus++;
338                 }
339                 if (available_spus < ctx->gang->contexts) {
340                         mutex_unlock(&cbe_spu_info[node].list_mutex);
341                         continue;
342                 }
343 
344                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
345                         if ((!mem_aff || spu->has_mem_affinity) &&
346                                                         sched_spu(spu)) {
347                                 mutex_unlock(&cbe_spu_info[node].list_mutex);
348                                 return spu;
349                         }
350                 }
351                 mutex_unlock(&cbe_spu_info[node].list_mutex);
352         }
353         return NULL;
354 }
355 
356 static void aff_set_ref_point_location(struct spu_gang *gang)
357 {
358         int mem_aff, gs, lowest_offset;
359         struct spu_context *ctx;
360         struct spu *tmp;
361 
362         mem_aff = gang->aff_ref_ctx->flags & SPU_CREATE_AFFINITY_MEM;
363         lowest_offset = 0;
364         gs = 0;
365 
366         list_for_each_entry(tmp, &gang->aff_list_head, aff_list)
367                 gs++;
368 
369         list_for_each_entry_reverse(ctx, &gang->aff_ref_ctx->aff_list,
370                                                                 aff_list) {
371                 if (&ctx->aff_list == &gang->aff_list_head)
372                         break;
373                 lowest_offset = ctx->aff_offset;
374         }
375 
376         gang->aff_ref_spu = aff_ref_location(gang->aff_ref_ctx, mem_aff, gs,
377                                                         lowest_offset);
378 }
379 
380 static struct spu *ctx_location(struct spu *ref, int offset, int node)
381 {
382         struct spu *spu;
383 
384         spu = NULL;
385         if (offset >= 0) {
386                 list_for_each_entry(spu, ref->aff_list.prev, aff_list) {
387                         BUG_ON(spu->node != node);
388                         if (offset == 0)
389                                 break;
390                         if (sched_spu(spu))
391                                 offset--;
392                 }
393         } else {
394                 list_for_each_entry_reverse(spu, ref->aff_list.next, aff_list) {
395                         BUG_ON(spu->node != node);
396                         if (offset == 0)
397                                 break;
398                         if (sched_spu(spu))
399                                 offset++;
400                 }
401         }
402 
403         return spu;
404 }
405 
406 /*
407  * affinity_check is called each time a context is going to be scheduled.
408  * It returns the spu ptr on which the context must run.
409  */
410 static int has_affinity(struct spu_context *ctx)
411 {
412         struct spu_gang *gang = ctx->gang;
413 
414         if (list_empty(&ctx->aff_list))
415                 return 0;
416 
417         if (atomic_read(&ctx->gang->aff_sched_count) == 0)
418                 ctx->gang->aff_ref_spu = NULL;
419 
420         if (!gang->aff_ref_spu) {
421                 if (!(gang->aff_flags & AFF_MERGED))
422                         aff_merge_remaining_ctxs(gang);
423                 if (!(gang->aff_flags & AFF_OFFSETS_SET))
424                         aff_set_offsets(gang);
425                 aff_set_ref_point_location(gang);
426         }
427 
428         return gang->aff_ref_spu != NULL;
429 }
430 
431 /**
432  * spu_unbind_context - unbind spu context from physical spu
433  * @spu:        physical spu to unbind from
434  * @ctx:        context to unbind
435  */
436 static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
437 {
438         u32 status;
439 
440         spu_context_trace(spu_unbind_context__enter, ctx, spu);
441 
442         spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
443 
444         if (spu->ctx->flags & SPU_CREATE_NOSCHED)
445                 atomic_dec(&cbe_spu_info[spu->node].reserved_spus);
446 
447         if (ctx->gang)
448                 /*
449                  * If ctx->gang->aff_sched_count is positive, SPU affinity is
450                  * being considered in this gang. Using atomic_dec_if_positive
451                  * allow us to skip an explicit check for affinity in this gang
452                  */
453                 atomic_dec_if_positive(&ctx->gang->aff_sched_count);
454 
455         spu_switch_notify(spu, NULL);
456         spu_unmap_mappings(ctx);
457         spu_save(&ctx->csa, spu);
458         spu_switch_log_notify(spu, ctx, SWITCH_LOG_STOP, 0);
459 
460         spin_lock_irq(&spu->register_lock);
461         spu->timestamp = jiffies;
462         ctx->state = SPU_STATE_SAVED;
463         spu->ibox_callback = NULL;
464         spu->wbox_callback = NULL;
465         spu->stop_callback = NULL;
466         spu->mfc_callback = NULL;
467         spu->pid = 0;
468         spu->tgid = 0;
469         ctx->ops = &spu_backing_ops;
470         spu->flags = 0;
471         spu->ctx = NULL;
472         spin_unlock_irq(&spu->register_lock);
473 
474         spu_associate_mm(spu, NULL);
475 
476         ctx->stats.slb_flt +=
477                 (spu->stats.slb_flt - ctx->stats.slb_flt_base);
478         ctx->stats.class2_intr +=
479                 (spu->stats.class2_intr - ctx->stats.class2_intr_base);
480 
481         /* This maps the underlying spu state to idle */
482         spuctx_switch_state(ctx, SPU_UTIL_IDLE_LOADED);
483         ctx->spu = NULL;
484 
485         if (spu_stopped(ctx, &status))
486                 wake_up_all(&ctx->stop_wq);
487 }
488 
489 /**
490  * spu_add_to_rq - add a context to the runqueue
491  * @ctx:       context to add
492  */
493 static void __spu_add_to_rq(struct spu_context *ctx)
494 {
495         /*
496          * Unfortunately this code path can be called from multiple threads
497          * on behalf of a single context due to the way the problem state
498          * mmap support works.
499          *
500          * Fortunately we need to wake up all these threads at the same time
501          * and can simply skip the runqueue addition for every but the first
502          * thread getting into this codepath.
503          *
504          * It's still quite hacky, and long-term we should proxy all other
505          * threads through the owner thread so that spu_run is in control
506          * of all the scheduling activity for a given context.
507          */
508         if (list_empty(&ctx->rq)) {
509                 list_add_tail(&ctx->rq, &spu_prio->runq[ctx->prio]);
510                 set_bit(ctx->prio, spu_prio->bitmap);
511                 if (!spu_prio->nr_waiting++)
512                         mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
513         }
514 }
515 
516 static void spu_add_to_rq(struct spu_context *ctx)
517 {
518         spin_lock(&spu_prio->runq_lock);
519         __spu_add_to_rq(ctx);
520         spin_unlock(&spu_prio->runq_lock);
521 }
522 
523 static void __spu_del_from_rq(struct spu_context *ctx)
524 {
525         int prio = ctx->prio;
526 
527         if (!list_empty(&ctx->rq)) {
528                 if (!--spu_prio->nr_waiting)
529                         del_timer(&spusched_timer);
530                 list_del_init(&ctx->rq);
531 
532                 if (list_empty(&spu_prio->runq[prio]))
533                         clear_bit(prio, spu_prio->bitmap);
534         }
535 }
536 
537 void spu_del_from_rq(struct spu_context *ctx)
538 {
539         spin_lock(&spu_prio->runq_lock);
540         __spu_del_from_rq(ctx);
541         spin_unlock(&spu_prio->runq_lock);
542 }
543 
544 static void spu_prio_wait(struct spu_context *ctx)
545 {
546         DEFINE_WAIT(wait);
547 
548         /*
549          * The caller must explicitly wait for a context to be loaded
550          * if the nosched flag is set.  If NOSCHED is not set, the caller
551          * queues the context and waits for an spu event or error.
552          */
553         BUG_ON(!(ctx->flags & SPU_CREATE_NOSCHED));
554 
555         spin_lock(&spu_prio->runq_lock);
556         prepare_to_wait_exclusive(&ctx->stop_wq, &wait, TASK_INTERRUPTIBLE);
557         if (!signal_pending(current)) {
558                 __spu_add_to_rq(ctx);
559                 spin_unlock(&spu_prio->runq_lock);
560                 mutex_unlock(&ctx->state_mutex);
561                 schedule();
562                 mutex_lock(&ctx->state_mutex);
563                 spin_lock(&spu_prio->runq_lock);
564                 __spu_del_from_rq(ctx);
565         }
566         spin_unlock(&spu_prio->runq_lock);
567         __set_current_state(TASK_RUNNING);
568         remove_wait_queue(&ctx->stop_wq, &wait);
569 }
570 
571 static struct spu *spu_get_idle(struct spu_context *ctx)
572 {
573         struct spu *spu, *aff_ref_spu;
574         int node, n;
575 
576         spu_context_nospu_trace(spu_get_idle__enter, ctx);
577 
578         if (ctx->gang) {
579                 mutex_lock(&ctx->gang->aff_mutex);
580                 if (has_affinity(ctx)) {
581                         aff_ref_spu = ctx->gang->aff_ref_spu;
582                         atomic_inc(&ctx->gang->aff_sched_count);
583                         mutex_unlock(&ctx->gang->aff_mutex);
584                         node = aff_ref_spu->node;
585 
586                         mutex_lock(&cbe_spu_info[node].list_mutex);
587                         spu = ctx_location(aff_ref_spu, ctx->aff_offset, node);
588                         if (spu && spu->alloc_state == SPU_FREE)
589                                 goto found;
590                         mutex_unlock(&cbe_spu_info[node].list_mutex);
591 
592                         atomic_dec(&ctx->gang->aff_sched_count);
593                         goto not_found;
594                 }
595                 mutex_unlock(&ctx->gang->aff_mutex);
596         }
597         node = cpu_to_node(raw_smp_processor_id());
598         for (n = 0; n < MAX_NUMNODES; n++, node++) {
599                 node = (node < MAX_NUMNODES) ? node : 0;
600                 if (!node_allowed(ctx, node))
601                         continue;
602 
603                 mutex_lock(&cbe_spu_info[node].list_mutex);
604                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
605                         if (spu->alloc_state == SPU_FREE)
606                                 goto found;
607                 }
608                 mutex_unlock(&cbe_spu_info[node].list_mutex);
609         }
610 
611  not_found:
612         spu_context_nospu_trace(spu_get_idle__not_found, ctx);
613         return NULL;
614 
615  found:
616         spu->alloc_state = SPU_USED;
617         mutex_unlock(&cbe_spu_info[node].list_mutex);
618         spu_context_trace(spu_get_idle__found, ctx, spu);
619         spu_init_channels(spu);
620         return spu;
621 }
622 
623 /**
624  * find_victim - find a lower priority context to preempt
625  * @ctx:        canidate context for running
626  *
627  * Returns the freed physical spu to run the new context on.
628  */
629 static struct spu *find_victim(struct spu_context *ctx)
630 {
631         struct spu_context *victim = NULL;
632         struct spu *spu;
633         int node, n;
634 
635         spu_context_nospu_trace(spu_find_victim__enter, ctx);
636 
637         /*
638          * Look for a possible preemption candidate on the local node first.
639          * If there is no candidate look at the other nodes.  This isn't
640          * exactly fair, but so far the whole spu scheduler tries to keep
641          * a strong node affinity.  We might want to fine-tune this in
642          * the future.
643          */
644  restart:
645         node = cpu_to_node(raw_smp_processor_id());
646         for (n = 0; n < MAX_NUMNODES; n++, node++) {
647                 node = (node < MAX_NUMNODES) ? node : 0;
648                 if (!node_allowed(ctx, node))
649                         continue;
650 
651                 mutex_lock(&cbe_spu_info[node].list_mutex);
652                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
653                         struct spu_context *tmp = spu->ctx;
654 
655                         if (tmp && tmp->prio > ctx->prio &&
656                             !(tmp->flags & SPU_CREATE_NOSCHED) &&
657                             (!victim || tmp->prio > victim->prio)) {
658                                 victim = spu->ctx;
659                         }
660                 }
661                 if (victim)
662                         get_spu_context(victim);
663                 mutex_unlock(&cbe_spu_info[node].list_mutex);
664 
665                 if (victim) {
666                         /*
667                          * This nests ctx->state_mutex, but we always lock
668                          * higher priority contexts before lower priority
669                          * ones, so this is safe until we introduce
670                          * priority inheritance schemes.
671                          *
672                          * XXX if the highest priority context is locked,
673                          * this can loop a long time.  Might be better to
674                          * look at another context or give up after X retries.
675                          */
676                         if (!mutex_trylock(&victim->state_mutex)) {
677                                 put_spu_context(victim);
678                                 victim = NULL;
679                                 goto restart;
680                         }
681 
682                         spu = victim->spu;
683                         if (!spu || victim->prio <= ctx->prio) {
684                                 /*
685                                  * This race can happen because we've dropped
686                                  * the active list mutex.  Not a problem, just
687                                  * restart the search.
688                                  */
689                                 mutex_unlock(&victim->state_mutex);
690                                 put_spu_context(victim);
691                                 victim = NULL;
692                                 goto restart;
693                         }
694 
695                         spu_context_trace(__spu_deactivate__unload, ctx, spu);
696 
697                         mutex_lock(&cbe_spu_info[node].list_mutex);
698                         cbe_spu_info[node].nr_active--;
699                         spu_unbind_context(spu, victim);
700                         mutex_unlock(&cbe_spu_info[node].list_mutex);
701 
702                         victim->stats.invol_ctx_switch++;
703                         spu->stats.invol_ctx_switch++;
704                         if (test_bit(SPU_SCHED_SPU_RUN, &victim->sched_flags))
705                                 spu_add_to_rq(victim);
706 
707                         mutex_unlock(&victim->state_mutex);
708                         put_spu_context(victim);
709 
710                         return spu;
711                 }
712         }
713 
714         return NULL;
715 }
716 
717 static void __spu_schedule(struct spu *spu, struct spu_context *ctx)
718 {
719         int node = spu->node;
720         int success = 0;
721 
722         spu_set_timeslice(ctx);
723 
724         mutex_lock(&cbe_spu_info[node].list_mutex);
725         if (spu->ctx == NULL) {
726                 spu_bind_context(spu, ctx);
727                 cbe_spu_info[node].nr_active++;
728                 spu->alloc_state = SPU_USED;
729                 success = 1;
730         }
731         mutex_unlock(&cbe_spu_info[node].list_mutex);
732 
733         if (success)
734                 wake_up_all(&ctx->run_wq);
735         else
736                 spu_add_to_rq(ctx);
737 }
738 
739 static void spu_schedule(struct spu *spu, struct spu_context *ctx)
740 {
741         /* not a candidate for interruptible because it's called either
742            from the scheduler thread or from spu_deactivate */
743         mutex_lock(&ctx->state_mutex);
744         if (ctx->state == SPU_STATE_SAVED)
745                 __spu_schedule(spu, ctx);
746         spu_release(ctx);
747 }
748 
749 /**
750  * spu_unschedule - remove a context from a spu, and possibly release it.
751  * @spu:        The SPU to unschedule from
752  * @ctx:        The context currently scheduled on the SPU
753  * @free_spu    Whether to free the SPU for other contexts
754  *
755  * Unbinds the context @ctx from the SPU @spu. If @free_spu is non-zero, the
756  * SPU is made available for other contexts (ie, may be returned by
757  * spu_get_idle). If this is zero, the caller is expected to schedule another
758  * context to this spu.
759  *
760  * Should be called with ctx->state_mutex held.
761  */
762 static void spu_unschedule(struct spu *spu, struct spu_context *ctx,
763                 int free_spu)
764 {
765         int node = spu->node;
766 
767         mutex_lock(&cbe_spu_info[node].list_mutex);
768         cbe_spu_info[node].nr_active--;
769         if (free_spu)
770                 spu->alloc_state = SPU_FREE;
771         spu_unbind_context(spu, ctx);
772         ctx->stats.invol_ctx_switch++;
773         spu->stats.invol_ctx_switch++;
774         mutex_unlock(&cbe_spu_info[node].list_mutex);
775 }
776 
777 /**
778  * spu_activate - find a free spu for a context and execute it
779  * @ctx:        spu context to schedule
780  * @flags:      flags (currently ignored)
781  *
782  * Tries to find a free spu to run @ctx.  If no free spu is available
783  * add the context to the runqueue so it gets woken up once an spu
784  * is available.
785  */
786 int spu_activate(struct spu_context *ctx, unsigned long flags)
787 {
788         struct spu *spu;
789 
790         /*
791          * If there are multiple threads waiting for a single context
792          * only one actually binds the context while the others will
793          * only be able to acquire the state_mutex once the context
794          * already is in runnable state.
795          */
796         if (ctx->spu)
797                 return 0;
798 
799 spu_activate_top:
800         if (signal_pending(current))
801                 return -ERESTARTSYS;
802 
803         spu = spu_get_idle(ctx);
804         /*
805          * If this is a realtime thread we try to get it running by
806          * preempting a lower priority thread.
807          */
808         if (!spu && rt_prio(ctx->prio))
809                 spu = find_victim(ctx);
810         if (spu) {
811                 unsigned long runcntl;
812 
813                 runcntl = ctx->ops->runcntl_read(ctx);
814                 __spu_schedule(spu, ctx);
815                 if (runcntl & SPU_RUNCNTL_RUNNABLE)
816                         spuctx_switch_state(ctx, SPU_UTIL_USER);
817 
818                 return 0;
819         }
820 
821         if (ctx->flags & SPU_CREATE_NOSCHED) {
822                 spu_prio_wait(ctx);
823                 goto spu_activate_top;
824         }
825 
826         spu_add_to_rq(ctx);
827 
828         return 0;
829 }
830 
831 /**
832  * grab_runnable_context - try to find a runnable context
833  *
834  * Remove the highest priority context on the runqueue and return it
835  * to the caller.  Returns %NULL if no runnable context was found.
836  */
837 static struct spu_context *grab_runnable_context(int prio, int node)
838 {
839         struct spu_context *ctx;
840         int best;
841 
842         spin_lock(&spu_prio->runq_lock);
843         best = find_first_bit(spu_prio->bitmap, prio);
844         while (best < prio) {
845                 struct list_head *rq = &spu_prio->runq[best];
846 
847                 list_for_each_entry(ctx, rq, rq) {
848                         /* XXX(hch): check for affinity here as well */
849                         if (__node_allowed(ctx, node)) {
850                                 __spu_del_from_rq(ctx);
851                                 goto found;
852                         }
853                 }
854                 best++;
855         }
856         ctx = NULL;
857  found:
858         spin_unlock(&spu_prio->runq_lock);
859         return ctx;
860 }
861 
862 static int __spu_deactivate(struct spu_context *ctx, int force, int max_prio)
863 {
864         struct spu *spu = ctx->spu;
865         struct spu_context *new = NULL;
866 
867         if (spu) {
868                 new = grab_runnable_context(max_prio, spu->node);
869                 if (new || force) {
870                         spu_unschedule(spu, ctx, new == NULL);
871                         if (new) {
872                                 if (new->flags & SPU_CREATE_NOSCHED)
873                                         wake_up(&new->stop_wq);
874                                 else {
875                                         spu_release(ctx);
876                                         spu_schedule(spu, new);
877                                         /* this one can't easily be made
878                                            interruptible */
879                                         mutex_lock(&ctx->state_mutex);
880                                 }
881                         }
882                 }
883         }
884 
885         return new != NULL;
886 }
887 
888 /**
889  * spu_deactivate - unbind a context from it's physical spu
890  * @ctx:        spu context to unbind
891  *
892  * Unbind @ctx from the physical spu it is running on and schedule
893  * the highest priority context to run on the freed physical spu.
894  */
895 void spu_deactivate(struct spu_context *ctx)
896 {
897         spu_context_nospu_trace(spu_deactivate__enter, ctx);
898         __spu_deactivate(ctx, 1, MAX_PRIO);
899 }
900 
901 /**
902  * spu_yield -  yield a physical spu if others are waiting
903  * @ctx:        spu context to yield
904  *
905  * Check if there is a higher priority context waiting and if yes
906  * unbind @ctx from the physical spu and schedule the highest
907  * priority context to run on the freed physical spu instead.
908  */
909 void spu_yield(struct spu_context *ctx)
910 {
911         spu_context_nospu_trace(spu_yield__enter, ctx);
912         if (!(ctx->flags & SPU_CREATE_NOSCHED)) {
913                 mutex_lock(&ctx->state_mutex);
914                 __spu_deactivate(ctx, 0, MAX_PRIO);
915                 mutex_unlock(&ctx->state_mutex);
916         }
917 }
918 
919 static noinline void spusched_tick(struct spu_context *ctx)
920 {
921         struct spu_context *new = NULL;
922         struct spu *spu = NULL;
923 
924         if (spu_acquire(ctx))
925                 BUG();  /* a kernel thread never has signals pending */
926 
927         if (ctx->state != SPU_STATE_RUNNABLE)
928                 goto out;
929         if (ctx->flags & SPU_CREATE_NOSCHED)
930                 goto out;
931         if (ctx->policy == SCHED_FIFO)
932                 goto out;
933 
934         if (--ctx->time_slice && test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
935                 goto out;
936 
937         spu = ctx->spu;
938 
939         spu_context_trace(spusched_tick__preempt, ctx, spu);
940 
941         new = grab_runnable_context(ctx->prio + 1, spu->node);
942         if (new) {
943                 spu_unschedule(spu, ctx, 0);
944                 if (test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
945                         spu_add_to_rq(ctx);
946         } else {
947                 spu_context_nospu_trace(spusched_tick__newslice, ctx);
948                 if (!ctx->time_slice)
949                         ctx->time_slice++;
950         }
951 out:
952         spu_release(ctx);
953 
954         if (new)
955                 spu_schedule(spu, new);
956 }
957 
958 /**
959  * count_active_contexts - count nr of active tasks
960  *
961  * Return the number of tasks currently running or waiting to run.
962  *
963  * Note that we don't take runq_lock / list_mutex here.  Reading
964  * a single 32bit value is atomic on powerpc, and we don't care
965  * about memory ordering issues here.
966  */
967 static unsigned long count_active_contexts(void)
968 {
969         int nr_active = 0, node;
970 
971         for (node = 0; node < MAX_NUMNODES; node++)
972                 nr_active += cbe_spu_info[node].nr_active;
973         nr_active += spu_prio->nr_waiting;
974 
975         return nr_active;
976 }
977 
978 /**
979  * spu_calc_load - update the avenrun load estimates.
980  *
981  * No locking against reading these values from userspace, as for
982  * the CPU loadavg code.
983  */
984 static void spu_calc_load(void)
985 {
986         unsigned long active_tasks; /* fixed-point */
987 
988         active_tasks = count_active_contexts() * FIXED_1;
989         CALC_LOAD(spu_avenrun[0], EXP_1, active_tasks);
990         CALC_LOAD(spu_avenrun[1], EXP_5, active_tasks);
991         CALC_LOAD(spu_avenrun[2], EXP_15, active_tasks);
992 }
993 
994 static void spusched_wake(unsigned long data)
995 {
996         mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
997         wake_up_process(spusched_task);
998 }
999 
1000 static void spuloadavg_wake(unsigned long data)
1001 {
1002         mod_timer(&spuloadavg_timer, jiffies + LOAD_FREQ);
1003         spu_calc_load();
1004 }
1005 
1006 static int spusched_thread(void *unused)
1007 {
1008         struct spu *spu;
1009         int node;
1010 
1011         while (!kthread_should_stop()) {
1012                 set_current_state(TASK_INTERRUPTIBLE);
1013                 schedule();
1014                 for (node = 0; node < MAX_NUMNODES; node++) {
1015                         struct mutex *mtx = &cbe_spu_info[node].list_mutex;
1016 
1017                         mutex_lock(mtx);
1018                         list_for_each_entry(spu, &cbe_spu_info[node].spus,
1019                                         cbe_list) {
1020                                 struct spu_context *ctx = spu->ctx;
1021 
1022                                 if (ctx) {
1023                                         get_spu_context(ctx);
1024                                         mutex_unlock(mtx);
1025                                         spusched_tick(ctx);
1026                                         mutex_lock(mtx);
1027                                         put_spu_context(ctx);
1028                                 }
1029                         }
1030                         mutex_unlock(mtx);
1031                 }
1032         }
1033 
1034         return 0;
1035 }
1036 
1037 void spuctx_switch_state(struct spu_context *ctx,
1038                 enum spu_utilization_state new_state)
1039 {
1040         unsigned long long curtime;
1041         signed long long delta;
1042         struct spu *spu;
1043         enum spu_utilization_state old_state;
1044         int node;
1045 
1046         curtime = ktime_get_ns();
1047         delta = curtime - ctx->stats.tstamp;
1048 
1049         WARN_ON(!mutex_is_locked(&ctx->state_mutex));
1050         WARN_ON(delta < 0);
1051 
1052         spu = ctx->spu;
1053         old_state = ctx->stats.util_state;
1054         ctx->stats.util_state = new_state;
1055         ctx->stats.tstamp = curtime;
1056 
1057         /*
1058          * Update the physical SPU utilization statistics.
1059          */
1060         if (spu) {
1061                 ctx->stats.times[old_state] += delta;
1062                 spu->stats.times[old_state] += delta;
1063                 spu->stats.util_state = new_state;
1064                 spu->stats.tstamp = curtime;
1065                 node = spu->node;
1066                 if (old_state == SPU_UTIL_USER)
1067                         atomic_dec(&cbe_spu_info[node].busy_spus);
1068                 if (new_state == SPU_UTIL_USER)
1069                         atomic_inc(&cbe_spu_info[node].busy_spus);
1070         }
1071 }
1072 
1073 #define LOAD_INT(x) ((x) >> FSHIFT)
1074 #define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
1075 
1076 static int show_spu_loadavg(struct seq_file *s, void *private)
1077 {
1078         int a, b, c;
1079 
1080         a = spu_avenrun[0] + (FIXED_1/200);
1081         b = spu_avenrun[1] + (FIXED_1/200);
1082         c = spu_avenrun[2] + (FIXED_1/200);
1083 
1084         /*
1085          * Note that last_pid doesn't really make much sense for the
1086          * SPU loadavg (it even seems very odd on the CPU side...),
1087          * but we include it here to have a 100% compatible interface.
1088          */
1089         seq_printf(s, "%d.%02d %d.%02d %d.%02d %ld/%d %d\n",
1090                 LOAD_INT(a), LOAD_FRAC(a),
1091                 LOAD_INT(b), LOAD_FRAC(b),
1092                 LOAD_INT(c), LOAD_FRAC(c),
1093                 count_active_contexts(),
1094                 atomic_read(&nr_spu_contexts),
1095                 task_active_pid_ns(current)->last_pid);
1096         return 0;
1097 }
1098 
1099 static int spu_loadavg_open(struct inode *inode, struct file *file)
1100 {
1101         return single_open(file, show_spu_loadavg, NULL);
1102 }
1103 
1104 static const struct file_operations spu_loadavg_fops = {
1105         .open           = spu_loadavg_open,
1106         .read           = seq_read,
1107         .llseek         = seq_lseek,
1108         .release        = single_release,
1109 };
1110 
1111 int __init spu_sched_init(void)
1112 {
1113         struct proc_dir_entry *entry;
1114         int err = -ENOMEM, i;
1115 
1116         spu_prio = kzalloc(sizeof(struct spu_prio_array), GFP_KERNEL);
1117         if (!spu_prio)
1118                 goto out;
1119 
1120         for (i = 0; i < MAX_PRIO; i++) {
1121                 INIT_LIST_HEAD(&spu_prio->runq[i]);
1122                 __clear_bit(i, spu_prio->bitmap);
1123         }
1124         spin_lock_init(&spu_prio->runq_lock);
1125 
1126         setup_timer(&spusched_timer, spusched_wake, 0);
1127         setup_timer(&spuloadavg_timer, spuloadavg_wake, 0);
1128 
1129         spusched_task = kthread_run(spusched_thread, NULL, "spusched");
1130         if (IS_ERR(spusched_task)) {
1131                 err = PTR_ERR(spusched_task);
1132                 goto out_free_spu_prio;
1133         }
1134 
1135         mod_timer(&spuloadavg_timer, 0);
1136 
1137         entry = proc_create("spu_loadavg", 0, NULL, &spu_loadavg_fops);
1138         if (!entry)
1139                 goto out_stop_kthread;
1140 
1141         pr_debug("spusched: tick: %d, min ticks: %d, default ticks: %d\n",
1142                         SPUSCHED_TICK, MIN_SPU_TIMESLICE, DEF_SPU_TIMESLICE);
1143         return 0;
1144 
1145  out_stop_kthread:
1146         kthread_stop(spusched_task);
1147  out_free_spu_prio:
1148         kfree(spu_prio);
1149  out:
1150         return err;
1151 }
1152 
1153 void spu_sched_exit(void)
1154 {
1155         struct spu *spu;
1156         int node;
1157 
1158         remove_proc_entry("spu_loadavg", NULL);
1159 
1160         del_timer_sync(&spusched_timer);
1161         del_timer_sync(&spuloadavg_timer);
1162         kthread_stop(spusched_task);
1163 
1164         for (node = 0; node < MAX_NUMNODES; node++) {
1165                 mutex_lock(&cbe_spu_info[node].list_mutex);
1166                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list)
1167                         if (spu->alloc_state != SPU_FREE)
1168                                 spu->alloc_state = SPU_FREE;
1169                 mutex_unlock(&cbe_spu_info[node].list_mutex);
1170         }
1171         kfree(spu_prio);
1172 }
1173 

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