Re: [Cbe-oss-dev] [RFC, PATCH 3/4] Add support to OProfile for profiling Cell BE SPUs -- update
From: Arnd Bergmann <arnd@arndb.de>
Date: 2007-01-30 04:24:42
Also in:
lkml
On Monday 29 January 2007 20:48, Maynard Johnson wrote:
Subject: Enable SPU switch notification to detect currently active SPU tasks. From: Maynard Johnson <redacted> 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 <redacted>
I looked through it again, and think I found a serious bug, but that should be easy enough to solve:
+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_switch_notify();
+ */
+ 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;[side note] There is a small whitespace breakage in here, please make sure you always use tabs for indenting, not space characters. [/side note]
quoted hunk ↗ jump to hunk
@@ -45,9 +45,10 @@ u64 pte_fault; *stat = ctx->ops->status_read(ctx); - if (ctx->state != SPU_STATE_RUNNABLE) - return 1; + 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;@@ -305,6 +306,7 @@ u32 *npc, u32 *event) { int ret; + struct spu * spu; u32 status; if (down_interruptible(&ctx->run_sema))@@ -318,8 +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_switch_notify(spu, ctx); + continue; + } + }
This is before spu_reacquire_runnable, so in case the spu got preempted at the same time when oprofile was enabled, ctx->spu is NULL, and you can't load the notify_active flag from it. On solution would be to move the notify_active flag from ctx->spu into ctx itself, but maybe there are other ways to solve this. Thanks, Arnd <><