Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=379018022071489a7dffee74db2a267465dab561
Commit:     379018022071489a7dffee74db2a267465dab561
Parent:     be7031773eded128675de6da778234a935c8d8ea
Author:     Christoph Hellwig <[EMAIL PROTECTED]>
AuthorDate: Fri Jun 29 10:57:51 2007 +1000
Committer:  Paul Mackerras <[EMAIL PROTECTED]>
CommitDate: Tue Jul 3 15:24:44 2007 +1000

    [POWERPC] spusched: Switch from workqueues to kthread + timer tick
    
    Get rid of the scheduler workqueues that complicated things a lot to
    a dedicated spu scheduler thread that gets woken by a traditional
    scheduler tick.  By default this scheduler tick runs a HZ * 10, aka
    one spu scheduler tick for every 10 cpu ticks.
    
    Currently the tick is not disabled when we have less context than
    available spus, but I will implement this later.
    
    Signed-off-by: Christoph Hellwig <[EMAIL PROTECTED]>
    Signed-off-by: Arnd Bergmann <[EMAIL PROTECTED]>
    Signed-off-by: Jeremy Kerr <[EMAIL PROTECTED]>
    Signed-off-by: Paul Mackerras <[EMAIL PROTECTED]>
---
 arch/powerpc/platforms/cell/spufs/context.c |    2 +-
 arch/powerpc/platforms/cell/spufs/run.c     |    6 +-
 arch/powerpc/platforms/cell/spufs/sched.c   |  142 +++++++++++++++------------
 arch/powerpc/platforms/cell/spufs/spufs.h   |   12 +--
 4 files changed, 86 insertions(+), 76 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/context.c 
b/arch/powerpc/platforms/cell/spufs/context.c
index 7c51cb5..f084667 100644
--- a/arch/powerpc/platforms/cell/spufs/context.c
+++ b/arch/powerpc/platforms/cell/spufs/context.c
@@ -56,7 +56,7 @@ struct spu_context *alloc_spu_context(struct spu_gang *gang)
        ctx->rt_priority = current->rt_priority;
        ctx->policy = current->policy;
        ctx->prio = current->prio;
-       INIT_DELAYED_WORK(&ctx->sched_work, spu_sched_tick);
+       ctx->time_slice = SPU_DEF_TIMESLICE;
        goto out;
 out_free:
        kfree(ctx);
diff --git a/arch/powerpc/platforms/cell/spufs/run.c 
b/arch/powerpc/platforms/cell/spufs/run.c
index 3ba30ce..89b02b6 100644
--- a/arch/powerpc/platforms/cell/spufs/run.c
+++ b/arch/powerpc/platforms/cell/spufs/run.c
@@ -144,7 +144,6 @@ static int spu_run_init(struct spu_context *ctx, u32 * npc)
                ctx->ops->runcntl_write(ctx, runcntl);
        } else {
                unsigned long mode = SPU_PRIVCNTL_MODE_NORMAL;
-               spu_start_tick(ctx);
                ctx->ops->npc_write(ctx, *npc);
                if (test_thread_flag(TIF_SINGLESTEP))
                        mode = SPU_PRIVCNTL_MODE_SINGLE_STEP;
@@ -160,7 +159,6 @@ static int spu_run_fini(struct spu_context *ctx, u32 * npc,
 {
        int ret = 0;
 
-       spu_stop_tick(ctx);
        *status = ctx->ops->status_read(ctx);
        *npc = ctx->ops->npc_read(ctx);
        spu_release(ctx);
@@ -330,10 +328,8 @@ long spufs_run_spu(struct file *file, struct spu_context 
*ctx,
 
                if (unlikely(ctx->state != SPU_STATE_RUNNABLE)) {
                        ret = spu_reacquire_runnable(ctx, npc, &status);
-                       if (ret) {
-                               spu_stop_tick(ctx);
+                       if (ret)
                                goto out2;
-                       }
                        continue;
                }
                ret = spu_process_events(ctx);
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c 
b/arch/powerpc/platforms/cell/spufs/sched.c
index 3b831e0..d673353 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -35,6 +35,7 @@
 #include <linux/numa.h>
 #include <linux/mutex.h>
 #include <linux/notifier.h>
+#include <linux/kthread.h>
 
 #include <asm/io.h>
 #include <asm/mmu_context.h>
@@ -45,6 +46,8 @@
 
 #define SPU_TIMESLICE  (HZ)
 
+#define SPUSCHED_TICK  (HZ / 100)
+
 struct spu_prio_array {
        DECLARE_BITMAP(bitmap, MAX_PRIO);
        struct list_head runq[MAX_PRIO];
@@ -54,7 +57,8 @@ struct spu_prio_array {
 };
 
 static struct spu_prio_array *spu_prio;
-static struct workqueue_struct *spu_sched_wq;
+static struct task_struct *spusched_task;
+static struct timer_list spusched_timer;
 
 static inline int node_allowed(int node)
 {
@@ -68,31 +72,6 @@ static inline int node_allowed(int node)
        return 1;
 }
 
-void spu_start_tick(struct spu_context *ctx)
-{
-       if (ctx->policy == SCHED_RR) {
-               /*
-                * Make sure the exiting bit is cleared.
-                */
-               clear_bit(SPU_SCHED_EXITING, &ctx->sched_flags);
-               mb();
-               queue_delayed_work(spu_sched_wq, &ctx->sched_work, 
SPU_TIMESLICE);
-       }
-}
-
-void spu_stop_tick(struct spu_context *ctx)
-{
-       if (ctx->policy == SCHED_RR) {
-               /*
-                * While the work can be rearming normally setting this flag
-                * makes sure it does not rearm itself anymore.
-                */
-               set_bit(SPU_SCHED_EXITING, &ctx->sched_flags);
-               mb();
-               cancel_delayed_work(&ctx->sched_work);
-       }
-}
-
 /**
  * spu_add_to_active_list - add spu to active list
  * @spu:       spu to add to the active list
@@ -104,6 +83,11 @@ static void spu_add_to_active_list(struct spu *spu)
        mutex_unlock(&spu_prio->active_mutex[spu->node]);
 }
 
+static void __spu_remove_from_active_list(struct spu *spu)
+{
+       list_del_init(&spu->list);
+}
+
 /**
  * spu_remove_from_active_list - remove spu from active list
  * @spu:       spu to remove from the active list
@@ -113,7 +97,7 @@ static void spu_remove_from_active_list(struct spu *spu)
        int node = spu->node;
 
        mutex_lock(&spu_prio->active_mutex[node]);
-       list_del_init(&spu->list);
+       __spu_remove_from_active_list(spu);
        mutex_unlock(&spu_prio->active_mutex[node]);
 }
 
@@ -161,7 +145,6 @@ static void spu_bind_context(struct spu *spu, struct 
spu_context *ctx)
        spu->timestamp = jiffies;
        spu_cpu_affinity_set(spu, raw_smp_processor_id());
        spu_switch_notify(spu, ctx);
-       spu_add_to_active_list(spu);
        ctx->state = SPU_STATE_RUNNABLE;
 }
 
@@ -175,7 +158,6 @@ static void spu_unbind_context(struct spu *spu, struct 
spu_context *ctx)
        pr_debug("%s: unbind pid=%d SPU=%d NODE=%d\n", __FUNCTION__,
                 spu->pid, spu->number, spu->node);
 
-       spu_remove_from_active_list(spu);
        spu_switch_notify(spu, NULL);
        spu_unmap_mappings(ctx);
        spu_save(&ctx->csa, spu);
@@ -312,6 +294,7 @@ static struct spu *find_victim(struct spu_context *ctx)
                                victim = NULL;
                                goto restart;
                        }
+                       spu_remove_from_active_list(spu);
                        spu_unbind_context(spu, victim);
                        mutex_unlock(&victim->state_mutex);
                        /*
@@ -354,6 +337,7 @@ int spu_activate(struct spu_context *ctx, unsigned long 
flags)
                        spu = find_victim(ctx);
                if (spu) {
                        spu_bind_context(spu, ctx);
+                       spu_add_to_active_list(spu);
                        return 0;
                }
 
@@ -397,6 +381,7 @@ static int __spu_deactivate(struct spu_context *ctx, int 
force, int max_prio)
        if (spu) {
                new = grab_runnable_context(max_prio);
                if (new || force) {
+                       spu_remove_from_active_list(spu);
                        spu_unbind_context(spu, ctx);
                        spu_free(spu);
                        if (new)
@@ -437,51 +422,78 @@ void spu_yield(struct spu_context *ctx)
        }
 }
 
-void spu_sched_tick(struct work_struct *work)
+static void spusched_tick(struct spu_context *ctx)
 {
-       struct spu_context *ctx =
-               container_of(work, struct spu_context, sched_work.work);
-       int preempted;
+       if (ctx->policy != SCHED_RR || --ctx->time_slice)
+               return;
 
        /*
-        * If this context is being stopped avoid rescheduling from the
-        * scheduler tick because we would block on the state_mutex.
-        * The caller will yield the spu later on anyway.
+        * Unfortunately active_mutex ranks outside of state_mutex, so
+        * we have to trylock here.  If we fail give the context another
+        * tick and try again.
         */
-       if (test_bit(SPU_SCHED_EXITING, &ctx->sched_flags))
-               return;
-
-       mutex_lock(&ctx->state_mutex);
-       preempted = __spu_deactivate(ctx, 0, ctx->prio + 1);
-       mutex_unlock(&ctx->state_mutex);
+       if (mutex_trylock(&ctx->state_mutex)) {
+               struct spu_context *new = grab_runnable_context(ctx->prio + 1);
+               if (new) {
+                       struct spu *spu = ctx->spu;
 
-       if (preempted) {
-               /*
-                * We need to break out of the wait loop in spu_run manually
-                * to ensure this context gets put on the runqueue again
-                * ASAP.
-                */
-               wake_up(&ctx->stop_wq);
+                       __spu_remove_from_active_list(spu);
+                       spu_unbind_context(spu, ctx);
+                       spu_free(spu);
+                       wake_up(&new->stop_wq);
+                       /*
+                        * We need to break out of the wait loop in
+                        * spu_run manually to ensure this context
+                        * gets put on the runqueue again ASAP.
+                        */
+                       wake_up(&ctx->stop_wq);
+               }
+               ctx->time_slice = SPU_DEF_TIMESLICE;
+               mutex_unlock(&ctx->state_mutex);
        } else {
-               spu_start_tick(ctx);
+               ctx->time_slice++;
        }
 }
 
+static void spusched_wake(unsigned long data)
+{
+       mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
+       wake_up_process(spusched_task);
+}
+
+static int spusched_thread(void *unused)
+{
+       struct spu *spu, *next;
+       int node;
+
+       setup_timer(&spusched_timer, spusched_wake, 0);
+       __mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
+
+       while (!kthread_should_stop()) {
+               set_current_state(TASK_INTERRUPTIBLE);
+               schedule();
+               for (node = 0; node < MAX_NUMNODES; node++) {
+                       mutex_lock(&spu_prio->active_mutex[node]);
+                       list_for_each_entry_safe(spu, next,
+                                                &spu_prio->active_list[node],
+                                                list)
+                               spusched_tick(spu->ctx);
+                       mutex_unlock(&spu_prio->active_mutex[node]);
+               }
+       }
+
+       del_timer_sync(&spusched_timer);
+       return 0;
+}
+
 int __init spu_sched_init(void)
 {
        int i;
 
-       spu_sched_wq = create_singlethread_workqueue("spusched");
-       if (!spu_sched_wq)
-               return 1;
-
        spu_prio = kzalloc(sizeof(struct spu_prio_array), GFP_KERNEL);
-       if (!spu_prio) {
-               printk(KERN_WARNING "%s: Unable to allocate priority queue.\n",
-                      __FUNCTION__);
-                      destroy_workqueue(spu_sched_wq);
-               return 1;
-       }
+       if (!spu_prio)
+               return -ENOMEM;
+
        for (i = 0; i < MAX_PRIO; i++) {
                INIT_LIST_HEAD(&spu_prio->runq[i]);
                __clear_bit(i, spu_prio->bitmap);
@@ -492,7 +504,14 @@ int __init spu_sched_init(void)
                INIT_LIST_HEAD(&spu_prio->active_list[i]);
        }
        spin_lock_init(&spu_prio->runq_lock);
+
+       spusched_task = kthread_run(spusched_thread, NULL, "spusched");
+       if (IS_ERR(spusched_task)) {
+               kfree(spu_prio);
+               return PTR_ERR(spusched_task);
+       }
        return 0;
+
 }
 
 void __exit spu_sched_exit(void)
@@ -500,6 +519,8 @@ void __exit spu_sched_exit(void)
        struct spu *spu, *tmp;
        int node;
 
+       kthread_stop(spusched_task);
+
        for (node = 0; node < MAX_NUMNODES; node++) {
                mutex_lock(&spu_prio->active_mutex[node]);
                list_for_each_entry_safe(spu, tmp, &spu_prio->active_list[node],
@@ -510,5 +531,4 @@ void __exit spu_sched_exit(void)
                mutex_unlock(&spu_prio->active_mutex[node]);
        }
        kfree(spu_prio);
-       destroy_workqueue(spu_sched_wq);
 }
diff --git a/arch/powerpc/platforms/cell/spufs/spufs.h 
b/arch/powerpc/platforms/cell/spufs/spufs.h
index 47617e8..8068171 100644
--- a/arch/powerpc/platforms/cell/spufs/spufs.h
+++ b/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -31,6 +31,8 @@
 #include <asm/spu_csa.h>
 #include <asm/spu_info.h>
 
+#define SPU_DEF_TIMESLICE      100
+
 /* The magic number for our file system */
 enum {
        SPUFS_MAGIC = 0x23c9b64e,
@@ -39,11 +41,6 @@ enum {
 struct spu_context_ops;
 struct spu_gang;
 
-/* ctx->sched_flags */
-enum {
-       SPU_SCHED_EXITING = 0,
-};
-
 struct spu_context {
        struct spu *spu;                  /* pointer to a physical SPU */
        struct spu_state csa;             /* SPU context save area. */
@@ -83,7 +80,7 @@ struct spu_context {
 
        /* scheduler fields */
        struct list_head rq;
-       struct delayed_work sched_work;
+       unsigned int time_slice;
        unsigned long sched_flags;
        unsigned long rt_priority;
        int policy;
@@ -200,9 +197,6 @@ void spu_acquire_saved(struct spu_context *ctx);
 int spu_activate(struct spu_context *ctx, unsigned long flags);
 void spu_deactivate(struct spu_context *ctx);
 void spu_yield(struct spu_context *ctx);
-void spu_start_tick(struct spu_context *ctx);
-void spu_stop_tick(struct spu_context *ctx);
-void spu_sched_tick(struct work_struct *work);
 int __init spu_sched_init(void);
 void __exit spu_sched_exit(void);
 
-
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