From b8e82670ce244434e7570fc4b0459628bd6beee1 Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Sat, 10 Oct 2015 13:52:47 -0700
Subject: [PATCH] Fix race conditions
---
src/core/transport/metadata.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/src/core/transport/metadata.c b/src/core/transport/metadata.c
index 1b48b48e09..68f23177eb 100644
--- a/src/core/transport/metadata.c
+++ b/src/core/transport/metadata.c
@@ -160,12 +160,10 @@ static void ref_md_locked(internal_metadata *md DEBUG_ARGS) {
grpc_mdstr_as_c_string((grpc_mdstr *)md->key),
grpc_mdstr_as_c_string((grpc_mdstr *)md->value));
#endif
- if (0 == gpr_atm_no_barrier_fetch_add(&md->refcnt, 1)) {
- /* This ref is dropped if grpc_mdelem_unref reaches 1,
- but allows us to safely unref without taking the mdctx lock
- until such time */
- gpr_atm_no_barrier_fetch_add(&md->refcnt, 1);
+ if (0 == gpr_atm_no_barrier_fetch_add(&md->refcnt, 2)) {
md->context->mdtab_free--;
+ } else {
+ GPR_ASSERT(1 != gpr_atm_no_barrier_fetch_add(&md->refcnt, -1));
}
}
@@ -537,7 +535,7 @@ grpc_mdelem *grpc_mdelem_ref(grpc_mdelem *gmd DEBUG_ARGS) {
this function - meaning that no adjustment to mdtab_free is necessary,
simplifying the logic here to be just an atomic increment */
/* use C assert to have this removed in opt builds */
- assert(gpr_atm_no_barrier_load(&md->refcnt) >= 1);
+ assert(gpr_atm_no_barrier_load(&md->refcnt) >= 2);
gpr_atm_no_barrier_fetch_add(&md->refcnt, 1);
return gmd;
}
@@ -555,8 +553,10 @@ void grpc_mdelem_unref(grpc_mdelem *gmd DEBUG_ARGS) {
if (2 == gpr_atm_full_fetch_add(&md->refcnt, -1)) {
grpc_mdctx *ctx = md->context;
lock(ctx);
- GPR_ASSERT(1 == gpr_atm_full_fetch_add(&md->refcnt, -1));
- ctx->mdtab_free++;
+ if (1 == gpr_atm_no_barrier_load(&md->refcnt)) {
+ ctx->mdtab_free++;
+ gpr_atm_no_barrier_store(&md->refcnt, 0);
+ }
unlock(ctx);
}
}
--
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