From 4ce09cf760db8771f9c9b222d6f06df61c058ff7 Mon Sep 17 00:00:00 2001
From: vjpai <vpai@google.com>
Date: Fri, 18 Mar 2016 23:09:15 -0700
Subject: [PATCH] Reorder a release store after the operations it protects.
---
src/core/iomgr/fd_posix.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/src/core/iomgr/fd_posix.c b/src/core/iomgr/fd_posix.c
index 4ba7c5df94..3edafa0b07 100644
--- a/src/core/iomgr/fd_posix.c
+++ b/src/core/iomgr/fd_posix.c
@@ -72,6 +72,9 @@ static grpc_fd *fd_freelist = NULL;
static gpr_mu fd_freelist_mu;
static void freelist_fd(grpc_fd *fd) {
+ // Note that this function must be called after a release store (or
+ // full-barrier operation) on refst so that prior actions on the fd are
+ // ordered before the fd becomes visible to the freelist
gpr_mu_lock(&fd_freelist_mu);
fd->freelist_next = fd_freelist;
fd_freelist = fd;
@@ -92,7 +95,6 @@ static grpc_fd *alloc_fd(int fd) {
gpr_mu_init(&r->mu);
}
- gpr_atm_rel_store(&r->refst, 1);
r->shutdown = 0;
r->read_closure = CLOSURE_NOT_READY;
r->write_closure = CLOSURE_NOT_READY;
@@ -104,6 +106,11 @@ static grpc_fd *alloc_fd(int fd) {
r->on_done_closure = NULL;
r->closed = 0;
r->released = 0;
+ // The last operation on r before returning it should be a release-store
+ // so that all the above fields are globally visible before the value of
+ // r could escape to another thread. Our refcount itself needs a release-store
+ // so use this
+ gpr_atm_rel_store(&r->refst, 1);
return r;
}
--
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