Re: [PATCH] Cell SPU task notification -- updated patch: #1
- From: Maynard Johnson <maynardj@xxxxxxxxxx>
- Date: Mon, 15 Jan 2007 16:39:32 -0600
Attached is an updated patch that addresses Michael Ellerman's comments.
One comment made by Michael has not yet been addressed:
The comment was in regard to the for-loop in spufs/sched.c:notify_spus_active(). He wondered if the scheduler can swap a context from one node to another. If so, there's a small window in this loop (where we switch the lock from one node's active list to the next) where it may be possible we might miss waking up a context and send a spurious wakeup to another.
Arnd . . . can you comment on this question?
Thanks.
-Maynard
Subject: Enable SPU switch notification to detect currently active SPU tasks.
From: Maynard Johnson <maynardj@xxxxxxxxxx>
This patch adds to the capability of spu_switch_event_register so that the
caller is also notified of currently active SPU tasks. It also exports
spu_switch_event_register and spu_switch_event_unregister.
Signed-off-by: Maynard Johnson <mpjohn@xxxxxxxxxx>
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 2007-01-15 16:22:31.808461448 -0600
@@ -84,15 +84,42 @@
ctx ? ctx->object_id : 0, spu);
}
+static void notify_spus_active(void)
+{
+ int node;
+ /* Wake up the active spu_contexts. When the awakened processes
+ * sees their notify_active flag is set, they will call
+ * spu_notify_already_active().
+ */
+ 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;
+ spu->notify_active = 1;
+ wake_up_all(&ctx->stop_wq);
+ smp_wmb();
+ }
+ mutex_unlock(&spu_prio->active_mutex[node]);
+ }
+ yield();
+}
+
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;
}
+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 +277,14 @@
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.
*
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 2007-01-15 16:31:30.104499992 -0600
@@ -45,9 +45,11 @@
u64 pte_fault;
*stat = ctx->ops->status_read(ctx);
- if (ctx->state != SPU_STATE_RUNNABLE)
- return 1;
+ smp_rmb();
+
spu = ctx->spu;
+ if (ctx->state != SPU_STATE_RUNNABLE || spu->notify_active)
+ return 1;
pte_fault = spu->dsisr &
(MFC_DSISR_PTE_NOT_FOUND | MFC_DSISR_ACCESS_DENIED);
return (!(*stat & 0x1) || pte_fault || spu->class_0_pending) ? 1 : 0;
@@ -304,6 +306,7 @@
u32 *npc, u32 *event)
{
int ret;
+ struct * spu;
u32 status;
if (down_interruptible(&ctx->run_sema))
@@ -317,8 +320,16 @@
do {
ret = spufs_wait(ctx->stop_wq, spu_stopped(ctx, &status));
+ spu = ctx->spu;
if (unlikely(ret))
break;
+ if (unlikely(spu->notify_active)) {
+ spu->notify_active = 0;
+ if (!(status & SPU_STATUS_STOPPED_BY_STOP)) {
+ spu_notify_already_active(ctx);
+ continue;
+ }
+ }
if ((status & SPU_STATUS_STOPPED_BY_STOP) &&
(status >> SPU_STOP_STATUS_SHIFT == 0x2104)) {
ret = spu_process_callback(ctx);
- References:
- [PATCH] Cell SPU task notification
- From: Maynard Johnson
- Re: [PATCH] Cell SPU task notification
- From: Michael Ellerman
- [PATCH] Cell SPU task notification
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