From 36ddbb1380f282b4280c57efdb646dd8647a789f Mon Sep 17 00:00:00 2001 From: Andre Detsch Date: Wed, 19 Sep 2007 14:38:12 +1000 Subject: [PATCH] [POWERPC] spufs: Fix race condition on gang->aff_ref_spu Affinity reference point location (gang->aff_ref_spu) is reset when the whole gang is descheduled. However, the last member of a gang can be descheduled while we are trying to schedule another member of the gang. This was leading to a race condition, and the code was using gang->aff_ref_spu in an unsafe manner. By holding the gang->aff_mutex a little bit longer, and increment gang->aff_sched_count (which controls when gang->aff_ref_spu should be reset) a little bit earlier, the problem is fixed. Signed-off-by: Andre Detsch Signed-off-by: Jeremy Kerr Signed-off-by: Paul Mackerras --- arch/powerpc/platforms/cell/spufs/sched.c | 49 +++++++++++++++-------- 1 file changed, 32 insertions(+), 17 deletions(-) diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c index c784edd40ea7..17806e001e50 100644 --- a/arch/powerpc/platforms/cell/spufs/sched.c +++ b/arch/powerpc/platforms/cell/spufs/sched.c @@ -230,8 +230,6 @@ static void spu_bind_context(struct spu *spu, struct spu_context *ctx) if (ctx->flags & SPU_CREATE_NOSCHED) atomic_inc(&cbe_spu_info[spu->node].reserved_spus); - if (!list_empty(&ctx->aff_list)) - atomic_inc(&ctx->gang->aff_sched_count); ctx->stats.slb_flt_base = spu->stats.slb_flt; ctx->stats.class2_intr_base = spu->stats.class2_intr; @@ -392,7 +390,6 @@ static int has_affinity(struct spu_context *ctx) if (list_empty(&ctx->aff_list)) return 0; - mutex_lock(&gang->aff_mutex); if (!gang->aff_ref_spu) { if (!(gang->aff_flags & AFF_MERGED)) aff_merge_remaining_ctxs(gang); @@ -400,7 +397,6 @@ static int has_affinity(struct spu_context *ctx) aff_set_offsets(gang); aff_set_ref_point_location(gang); } - mutex_unlock(&gang->aff_mutex); return gang->aff_ref_spu != NULL; } @@ -418,9 +414,16 @@ static void spu_unbind_context(struct spu *spu, struct spu_context *ctx) if (spu->ctx->flags & SPU_CREATE_NOSCHED) atomic_dec(&cbe_spu_info[spu->node].reserved_spus); - if (!list_empty(&ctx->aff_list)) - if (atomic_dec_and_test(&ctx->gang->aff_sched_count)) - ctx->gang->aff_ref_spu = NULL; + + if (ctx->gang){ + mutex_lock(&ctx->gang->aff_mutex); + if (has_affinity(ctx)) { + if (atomic_dec_and_test(&ctx->gang->aff_sched_count)) + ctx->gang->aff_ref_spu = NULL; + } + mutex_unlock(&ctx->gang->aff_mutex); + } + spu_switch_notify(spu, NULL); spu_unmap_mappings(ctx); spu_save(&ctx->csa, spu); @@ -511,20 +514,32 @@ static void spu_prio_wait(struct spu_context *ctx) static struct spu *spu_get_idle(struct spu_context *ctx) { - struct spu *spu; + struct spu *spu, *aff_ref_spu; int node, n; - if (has_affinity(ctx)) { - node = ctx->gang->aff_ref_spu->node; + if (ctx->gang) { + mutex_lock(&ctx->gang->aff_mutex); + if (has_affinity(ctx)) { + aff_ref_spu = ctx->gang->aff_ref_spu; + atomic_inc(&ctx->gang->aff_sched_count); + mutex_unlock(&ctx->gang->aff_mutex); + node = aff_ref_spu->node; - mutex_lock(&cbe_spu_info[node].list_mutex); - spu = ctx_location(ctx->gang->aff_ref_spu, ctx->aff_offset, node); - if (spu && spu->alloc_state == SPU_FREE) - goto found; - mutex_unlock(&cbe_spu_info[node].list_mutex); - return NULL; - } + mutex_lock(&cbe_spu_info[node].list_mutex); + spu = ctx_location(aff_ref_spu, ctx->aff_offset, node); + if (spu && spu->alloc_state == SPU_FREE) + goto found; + mutex_unlock(&cbe_spu_info[node].list_mutex); + mutex_lock(&ctx->gang->aff_mutex); + if (atomic_dec_and_test(&ctx->gang->aff_sched_count)) + ctx->gang->aff_ref_spu = NULL; + mutex_unlock(&ctx->gang->aff_mutex); + + return NULL; + } + mutex_unlock(&ctx->gang->aff_mutex); + } node = cpu_to_node(raw_smp_processor_id()); for (n = 0; n < MAX_NUMNODES; n++, node++) { node = (node < MAX_NUMNODES) ? node : 0; -- 2.30.2