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
  41struct 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
  48static unsigned long spu_avenrun[3];
  49static struct spu_prio_array *spu_prio;
  50static struct task_struct *spusched_task;
  51static struct timer_list spusched_timer;
  52static 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 */
  85void 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 */
  96void __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
 137void 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
 155static 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
 167static 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
 178void 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 */
 210static 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 */
 251static 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
 258static 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
 269static 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
 292static 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
 344static 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
 368static 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 */
 398static 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 */
 424static 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 */
 481static 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
 504static 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
 511static 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
 525void 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
 532static 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
 559static 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 */
 617static 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
 705static 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
 727static 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 */
 750static 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 */
 774int 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
 787spu_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 */
 825static 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
 850static 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 */
 883void 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 */
 897void 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
 907static 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        }
 939out:
 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 */
 955static 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 */
 972static 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
 982static void spusched_wake(struct timer_list *unused)
 983{
 984        mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
 985        wake_up_process(spusched_task);
 986}
 987
 988static void spuloadavg_wake(struct timer_list *unused)
 989{
 990        mod_timer(&spuloadavg_timer, jiffies + LOAD_FREQ);
 991        spu_calc_load();
 992}
 993
 994static 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
1025void 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
1061static 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
1084int __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
1126void 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