powerpc/spufs: fix aff_mutex and cbe_spu_info[n].list_mutex deadlock

Currenlt,, it is possible to lock aff_mutex and
cbe_spu_info[n].list_mutex in different orders, allowing a deadlock to
occur. With this change, aff_mutex is not taken within a list_mutex
critical section anymore.

Signed-off-by: Andre Detsch <adetsch@br.ibm.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 34654743363dccf871534441f36bbcf2149459ef..f293963cd855adf264e6d7ec55d6c3784cb04af9 100644 (file)
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -389,6 +389,9 @@ static int has_affinity(struct spu_context *ctx)
        if (list_empty(&ctx->aff_list))
                return 0;
 
+       if (atomic_read(&ctx->gang->aff_sched_count) == 0)
+               ctx->gang->aff_ref_spu = NULL;
+
        if (!gang->aff_ref_spu) {
                if (!(gang->aff_flags & AFF_MERGED))
                        aff_merge_remaining_ctxs(gang);
@@ -416,14 +419,8 @@ 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 (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);
-       }
+       if (ctx->gang)
+               atomic_dec_if_positive(&ctx->gang->aff_sched_count);
 
        spu_switch_notify(spu, NULL);
        spu_unmap_mappings(ctx);
@@ -562,10 +559,7 @@ static struct spu *spu_get_idle(struct spu_context *ctx)
                                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);
+                       atomic_dec(&ctx->gang->aff_sched_count);
                        goto not_found;
                }
                mutex_unlock(&ctx->gang->aff_mutex);