From eef4c2570d7bc8dbe314403a68bff2500722c07d Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Mon, 13 Jul 2015 16:25:21 -0700
Subject: [PATCH] Add a detectable edge for the first insert (so far untested)
---
src/core/support/stack_lockfree.c | 3 ++-
src/core/support/stack_lockfree.h | 3 ++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/src/core/support/stack_lockfree.c b/src/core/support/stack_lockfree.c
index 83a68444f5..598aa9cdf1 100644
--- a/src/core/support/stack_lockfree.c
+++ b/src/core/support/stack_lockfree.c
@@ -95,7 +95,7 @@ void gpr_stack_lockfree_destroy(gpr_stack_lockfree *stack) {
gpr_free(stack);
}
-void gpr_stack_lockfree_push(gpr_stack_lockfree *stack, int entry) {
+int gpr_stack_lockfree_push(gpr_stack_lockfree *stack, int entry) {
lockfree_node head;
lockfree_node newhead;
@@ -112,6 +112,7 @@ void gpr_stack_lockfree_push(gpr_stack_lockfree *stack, int entry) {
} while (!gpr_atm_rel_cas(&(stack->head.atm),
head.atm, newhead.atm));
/* Use rel_cas above to make sure that entry index is set properly */
+ return head.atm == INVALID_ENTRY_INDEX;
}
int gpr_stack_lockfree_pop(gpr_stack_lockfree *stack) {
diff --git a/src/core/support/stack_lockfree.h b/src/core/support/stack_lockfree.h
index 7919ef38cc..4da3572deb 100644
--- a/src/core/support/stack_lockfree.h
+++ b/src/core/support/stack_lockfree.h
@@ -42,7 +42,8 @@ gpr_stack_lockfree *gpr_stack_lockfree_create(int entries);
void gpr_stack_lockfree_destroy(gpr_stack_lockfree *);
/* Pass in a valid entry number for the next stack entry */
-void gpr_stack_lockfree_push(gpr_stack_lockfree *, int entry);
+/* Returns 1 if this is the first element on the stack, 0 otherwise */
+int gpr_stack_lockfree_push(gpr_stack_lockfree *, int entry);
/* Returns -1 on empty or the actual entry number */
int gpr_stack_lockfree_pop(gpr_stack_lockfree *);
--
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