From 4ef110141b3e0758fe30d686417b5686b87eb25b Mon Sep 17 00:00:00 2001 From: Jeremy Kerr Date: Tue, 19 Feb 2008 10:05:35 +1100 Subject: [POWERPC] spufs: fix scheduler starvation by idle contexts 2.6.25 has a regression where we can starve the scheduler by creating (N_SPES+1) contexts, then running them one at a time. The final context will never be run, as the other contexts are loaded on the SPEs, none of which are repoted as free (ie, spu->alloc_state != SPU_FREE), so spu_get_idle() doesn't give us a spu to run on. Because all of the contexts are stopped, none are descheduled by the scheduler tick, as spusched_tick returns if spu_stopped(ctx). This change replaces the spu_stopped() check with checking for SCHED_IDLE in ctx->policy. We set a context's policy to SCHED_IDLE when we're not in spu_run(). We also favour SCHED_IDLE contexts when looking for contexts to unbind, but leave their timeslice intact for later resumption. This patch fixes the following test in the spufs-testsuite: tests/20-scheduler/02-yield-starvation Signed-off-by: Jeremy Kerr --- arch/powerpc/platforms/cell/spufs/run.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/powerpc/platforms/cell/spufs/run.c') diff --git a/arch/powerpc/platforms/cell/spufs/run.c b/arch/powerpc/platforms/cell/spufs/run.c index fca22e18069..6221968c2a3 100644 --- a/arch/powerpc/platforms/cell/spufs/run.c +++ b/arch/powerpc/platforms/cell/spufs/run.c @@ -234,6 +234,7 @@ static int spu_run_fini(struct spu_context *ctx, u32 *npc, *npc = ctx->ops->npc_read(ctx); spuctx_switch_state(ctx, SPU_UTIL_IDLE_LOADED); + ctx->policy = SCHED_IDLE; spu_release(ctx); if (signal_pending(current)) -- cgit v1.2.3