From b65fe0356b5b732d7e1e0224c6a1cf2eb5255984 Mon Sep 17 00:00:00 2001 From: Jeremy Kerr Date: Thu, 4 Sep 2008 15:02:47 +1000 Subject: [PATCH] powerpc/spufs: Fix race for a free SPU We currently have a race for a free SPE. With one thread doing a spu_yield(), and another doing a spu_activate(): thread 1 thread 2 spu_yield(oldctx) spu_activate(ctx) __spu_deactivate(oldctx) spu_unschedule(oldctx, spu) spu->alloc_state = SPU_FREE spu = spu_get_idle(ctx) - searches for a SPE in state SPU_FREE, gets the context just freed by thread 1 spu_schedule(ctx, spu) spu->alloc_state = SPU_USED spu_schedule(newctx, spu) - assumes spu is still free - tries to schedule context on already-used spu This change introduces a 'free_spu' flag to spu_unschedule, to indicate whether or not the function should free the spu after descheduling the context. We only set this flag if we're not going to re-schedule another context on this SPU. Add a comment to document this behaviour. Signed-off-by: Jeremy Kerr --- arch/powerpc/platforms/cell/spufs/sched.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c index 9bb45c6b839..897c7406116 100644 --- a/arch/powerpc/platforms/cell/spufs/sched.c +++ b/arch/powerpc/platforms/cell/spufs/sched.c @@ -732,13 +732,28 @@ static void spu_schedule(struct spu *spu, struct spu_context *ctx) spu_release(ctx); } -static void spu_unschedule(struct spu *spu, struct spu_context *ctx) +/** + * spu_unschedule - remove a context from a spu, and possibly release it. + * @spu: The SPU to unschedule from + * @ctx: The context currently scheduled on the SPU + * @free_spu Whether to free the SPU for other contexts + * + * Unbinds the context @ctx from the SPU @spu. If @free_spu is non-zero, the + * SPU is made available for other contexts (ie, may be returned by + * spu_get_idle). If this is zero, the caller is expected to schedule another + * context to this spu. + * + * Should be called with ctx->state_mutex held. + */ +static void spu_unschedule(struct spu *spu, struct spu_context *ctx, + int free_spu) { int node = spu->node; mutex_lock(&cbe_spu_info[node].list_mutex); cbe_spu_info[node].nr_active--; - spu->alloc_state = SPU_FREE; + if (free_spu) + spu->alloc_state = SPU_FREE; spu_unbind_context(spu, ctx); ctx->stats.invol_ctx_switch++; spu->stats.invol_ctx_switch++; @@ -838,7 +853,7 @@ static int __spu_deactivate(struct spu_context *ctx, int force, int max_prio) if (spu) { new = grab_runnable_context(max_prio, spu->node); if (new || force) { - spu_unschedule(spu, ctx); + spu_unschedule(spu, ctx, new == NULL); if (new) { if (new->flags & SPU_CREATE_NOSCHED) wake_up(&new->stop_wq); @@ -911,7 +926,7 @@ static noinline void spusched_tick(struct spu_context *ctx) new = grab_runnable_context(ctx->prio + 1, spu->node); if (new) { - spu_unschedule(spu, ctx); + spu_unschedule(spu, ctx, 0); if (test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags)) spu_add_to_rq(ctx); } else { -- 2.41.0