[Cbe-oss-dev] [PATCH -- RFC]Add notification for active Cell SPU tasks -- update #2
Maynard Johnson
maynardj at us.ibm.com
Wed Jan 10 04:59:43 EST 2007
My statement below indicating that the first execution of this new SPU
notication code works properly was wrong. Even the first execution will
usually have one or more PPE processes that don't get awakened. It
dawned on me that since I'm using a global variable as a flag (assigned
in one process and checked in another), I should use smp_wmb() on the
assignment side and smp_rmb() on the PPE process side that checks the
flag. But that didn't help. Oddly, when I put a printk in the new
notify_spus_active function just prior to setting the notify_profiler
flag, then everything works -- with or without memory barriers! I'm
still investigating this, but I wanted to re-post to clear up my
incorrect statement from yesterday.
-Maynard
Maynard Johnson wrote:
> The attached patch adds notification of already-active SPU tasks to
> SPUFS. However, there's a bug that I'm having trouble finding. The
> first execution of this code path works fine, but subsequent runs do not
> work properly. On subsequent runs, I can see that not all of the
> already-active tasks are getting awakened, so my OProfile driver is not
> able to collect samples for those SPU contexts that were not awakened.
> If anyone can see the error in my logic or if you have any other
> comments on this patch, I would appreciate it.
>
> Thanks.
>
> Maynard
>
>------------------------------------------------------------------------
>
>Subject: Enable SPU switch notification to detect currently active SPU tasks.
>
>From: Maynard Johnson <maynardj at us.ibm.com>
>
>This patch adds to the capability of spu_switch_event_register to notify the
>caller of currently active SPU tasks. It also exports spu_switch_event_register
>and spu_switch_event_unregister.
>
>Signed-off-by: Maynard Johnson <mpjohn at us.ibm.com>
>
>
>Index: linux-2.6.19-rc6-arnd1+patches/arch/powerpc/platforms/cell/spufs/sched.c
>===================================================================
>--- linux-2.6.19-rc6-arnd1+patches.orig/arch/powerpc/platforms/cell/spufs/sched.c 2006-12-04 10:56:04.730698720 -0600
>+++ linux-2.6.19-rc6-arnd1+patches/arch/powerpc/platforms/cell/spufs/sched.c 2007-01-08 18:37:19.209355672 -0600
>@@ -46,6 +46,10 @@
>
> #define SPU_MIN_TIMESLICE (100 * HZ / 1000)
>
>+int notify_profiler;
>+
>+struct list_head active_spu_ctx_cache[MAX_NUMNODES];
>+
> #define SPU_BITMAP_SIZE (((MAX_PRIO+BITS_PER_LONG)/BITS_PER_LONG)+1)
> struct spu_prio_array {
> unsigned long bitmap[SPU_BITMAP_SIZE];
>@@ -81,19 +85,62 @@
> static void spu_switch_notify(struct spu *spu, struct spu_context *ctx)
> {
> blocking_notifier_call_chain(&spu_switch_notifier,
>- ctx ? ctx->object_id : 0, spu);
>+ ctx ? ctx->object_id : 0, spu);
>+}
>+
>+static void notify_spus_active(void)
>+{
>+ int node;
>+ /* Obtain and cache the active spu_contexts. */
>+ for (node = 0; node < MAX_NUMNODES; node++) {
>+ struct spu *spu;
>+ mutex_lock(&spu_prio->active_mutex[node]);
>+ list_for_each_entry(spu, &spu_prio->active_list[node],
>+ list) {
>+ struct spu_context *ctx = spu->ctx;
>+ /* Make sure the context doesn't go away before we use it. */
>+ get_spu_context(ctx);
>+ list_add(&ctx->active_cache_list,
>+ &active_spu_ctx_cache[node]);
>+ }
>+ mutex_unlock(&spu_prio->active_mutex[node]);
>+ }
>+ /* Now wake up the PPE tasks associated with the active spu contexts
>+ * we found above.
>+ */
>+ for (node = 0; node < MAX_NUMNODES; node++) {
>+ struct spu_context *ctx, *tmp;
>+ list_for_each_entry_safe(ctx, tmp,
>+ &active_spu_ctx_cache[node],
>+ active_cache_list) {
>+ notify_profiler = 1;
>+ wake_up_all(&ctx->stop_wq);
>+ list_del(&ctx->active_cache_list);
>+ put_spu_context(ctx);
>+ set_current_state(TASK_RUNNING);
>+ schedule();
>+ }
>+ }
> }
>
>-int spu_switch_event_register(struct notifier_block * n)
>+int spu_switch_event_register(struct notifier_block *n)
> {
>- return blocking_notifier_chain_register(&spu_switch_notifier, n);
>+ int ret;
>+ ret = blocking_notifier_chain_register(&spu_switch_notifier, n);
>+ if (!ret)
>+ notify_spus_active();
>+ return ret;
> }
>
>-int spu_switch_event_unregister(struct notifier_block * n)
>+EXPORT_SYMBOL_GPL(spu_switch_event_register);
>+
>+int spu_switch_event_unregister(struct notifier_block *n)
> {
> return blocking_notifier_chain_unregister(&spu_switch_notifier, n);
> }
>
>+EXPORT_SYMBOL_GPL(spu_switch_event_unregister);
>+
>
> static inline void bind_context(struct spu *spu, struct spu_context *ctx)
> {
>@@ -250,6 +297,14 @@
> return spu_get_idle(ctx, flags);
> }
>
>+void spu_notify_already_active(struct spu_context *ctx)
>+{
>+ struct spu *spu = ctx->spu;
>+ if (!spu)
>+ return;
>+ spu_switch_notify(spu, ctx);
>+}
>+
> /* The three externally callable interfaces
> * for the scheduler begin here.
> *
>@@ -345,6 +400,7 @@
> for (i = 0; i < MAX_NUMNODES; i++) {
> mutex_init(&spu_prio->active_mutex[i]);
> INIT_LIST_HEAD(&spu_prio->active_list[i]);
>+ INIT_LIST_HEAD(&active_spu_ctx_cache[i]);
> }
> return 0;
> }
>Index: linux-2.6.19-rc6-arnd1+patches/arch/powerpc/platforms/cell/spufs/spufs.h
>===================================================================
>--- linux-2.6.19-rc6-arnd1+patches.orig/arch/powerpc/platforms/cell/spufs/spufs.h 2007-01-08 18:18:40.093354608 -0600
>+++ linux-2.6.19-rc6-arnd1+patches/arch/powerpc/platforms/cell/spufs/spufs.h 2007-01-08 18:31:03.610345792 -0600
>@@ -183,6 +183,7 @@
> void spu_yield(struct spu_context *ctx);
> int __init spu_sched_init(void);
> void __exit spu_sched_exit(void);
>+void spu_notify_already_active(struct spu_context *ctx);
>
> extern char *isolated_loader;
>
>Index: linux-2.6.19-rc6-arnd1+patches/arch/powerpc/platforms/cell/spufs/run.c
>===================================================================
>--- linux-2.6.19-rc6-arnd1+patches.orig/arch/powerpc/platforms/cell/spufs/run.c 2007-01-08 18:33:51.979311680 -0600
>+++ linux-2.6.19-rc6-arnd1+patches/arch/powerpc/platforms/cell/spufs/run.c 2007-01-08 18:34:09.260344944 -0600
>@@ -10,6 +10,8 @@
>
> #include "spufs.h"
>
>+extern int notify_profiler;
>+
> /* interrupt-level stop callback function. */
> void spufs_stop_callback(struct spu *spu)
> {
>@@ -45,7 +47,7 @@
> u64 pte_fault;
>
> *stat = ctx->ops->status_read(ctx);
>- if (ctx->state != SPU_STATE_RUNNABLE)
>+ if (ctx->state != SPU_STATE_RUNNABLE || notify_profiler)
> return 1;
> spu = ctx->spu;
> pte_fault = spu->dsisr &
>@@ -319,6 +321,10 @@
> ret = spufs_wait(ctx->stop_wq, spu_stopped(ctx, &status));
> if (unlikely(ret))
> break;
>+ if (unlikely(notify_profiler)) {
>+ spu_notify_already_active(ctx);
>+ notify_profiler = 0;
>+ }
> if ((status & SPU_STATUS_STOPPED_BY_STOP) &&
> (status >> SPU_STOP_STATUS_SHIFT == 0x2104)) {
> ret = spu_process_callback(ctx);
>
>
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