From: Jeremy Kerr <jk@ozlabs.org>
Date: Wed, 27 Feb 2008 08:08:13 +0000 (+1100)
Subject: [POWERPC] spufs: fix invalid scheduling of forgotten contexts
X-Git-Tag: v2.6.25-rc4~120^2~1^2~5
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0111a701867a796a7ca6ecbc385e4befc9f35066;p=linux-2.6

[POWERPC] spufs: fix invalid scheduling of forgotten contexts

At present, we have a situation where a context with no owner is
re-scheduled by spu_forget:

	Thread 1: reading regs file	Thread 2: context owner

					spu_forget()
						- ctx->owner = NULL
						- set SPU_SCHED_WAS_ACTIVE

	spu_acquire_saved()
	- context is in saved state

	spu_release_saved()
	- SPU_SCHED_WAS_ACTIVE is set,
	  so spu_activate() the context,
	  which now has no owner

In spu_forget(), we shouldn't be requesting a re-schedule by setting
SPU_SCHED_WAS_ACTIVE. This change removes the set_bit in spu_forget(),
so that spu_release_saved() doesn't reinsert this destroyed context on
to the run queue.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
---

diff --git a/arch/powerpc/platforms/cell/spufs/context.c b/arch/powerpc/platforms/cell/spufs/context.c
index 133995ed5c..cf6c2c8921 100644
--- a/arch/powerpc/platforms/cell/spufs/context.c
+++ b/arch/powerpc/platforms/cell/spufs/context.c
@@ -109,13 +109,12 @@ void spu_forget(struct spu_context *ctx)
 
 	/*
 	 * This is basically an open-coded spu_acquire_saved, except that
-	 * we don't acquire the state mutex interruptible.
+	 * we don't acquire the state mutex interruptible, and we don't
+	 * want this context to be rescheduled on release.
 	 */
 	mutex_lock(&ctx->state_mutex);
-	if (ctx->state != SPU_STATE_SAVED) {
-		set_bit(SPU_SCHED_WAS_ACTIVE, &ctx->sched_flags);
+	if (ctx->state != SPU_STATE_SAVED)
 		spu_deactivate(ctx);
-	}
 
 	mm = ctx->owner;
 	ctx->owner = NULL;