Merge branch 'master' of https://github.com/grpc/grpc into channel-tracing

1 files changed, 84 insertions, 0 deletions

diff --git a/src/core/lib/gpr/mpscq.h b/src/core/lib/gpr/mpscq.h
new file mode 100644
index 0000000000..4409c5c9f5
--- /dev/null
+++ b/src/core/lib/gpr/mpscq.h
@@ -0,0 +1,84 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_GPR_MPSCQ_H
+#define GRPC_CORE_LIB_GPR_MPSCQ_H
+
+#include <grpc/support/atm.h>
+#include <grpc/support/sync.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+// Multiple-producer single-consumer lock free queue, based upon the
+// implementation from Dmitry Vyukov here:
+// http://www.1024cores.net/home/lock-free-algorithms/queues/intrusive-mpsc-node-based-queue
+
+// List node (include this in a data structure at the top, and add application
+// fields after it - to simulate inheritance)
+typedef struct gpr_mpscq_node {
+  gpr_atm next;
+} gpr_mpscq_node;
+
+// Actual queue type
+typedef struct gpr_mpscq {
+  gpr_atm head;
+  // make sure head & tail don't share a cacheline
+  char padding[GPR_CACHELINE_SIZE];
+  gpr_mpscq_node* tail;
+  gpr_mpscq_node stub;
+} gpr_mpscq;
+
+void gpr_mpscq_init(gpr_mpscq* q);
+void gpr_mpscq_destroy(gpr_mpscq* q);
+// Push a node
+// Thread safe - can be called from multiple threads concurrently
+// Returns true if this was possibly the first node (may return true
+// sporadically, will not return false sporadically)
+bool gpr_mpscq_push(gpr_mpscq* q, gpr_mpscq_node* n);
+// Pop a node (returns NULL if no node is ready - which doesn't indicate that
+// the queue is empty!!)
+// Thread compatible - can only be called from one thread at a time
+gpr_mpscq_node* gpr_mpscq_pop(gpr_mpscq* q);
+// Pop a node; sets *empty to true if the queue is empty, or false if it is not
+gpr_mpscq_node* gpr_mpscq_pop_and_check_end(gpr_mpscq* q, bool* empty);
+
+// An mpscq with a lock: it's safe to pop from multiple threads, but doing
+// only one thread will succeed concurrently
+typedef struct gpr_locked_mpscq {
+  gpr_mpscq queue;
+  gpr_mu mu;
+} gpr_locked_mpscq;
+
+void gpr_locked_mpscq_init(gpr_locked_mpscq* q);
+void gpr_locked_mpscq_destroy(gpr_locked_mpscq* q);
+// Push a node
+// Thread safe - can be called from multiple threads concurrently
+// Returns true if this was possibly the first node (may return true
+// sporadically, will not return false sporadically)
+bool gpr_locked_mpscq_push(gpr_locked_mpscq* q, gpr_mpscq_node* n);
+
+// Pop a node (returns NULL if no node is ready - which doesn't indicate that
+// the queue is empty!!)
+// Thread safe - can be called from multiple threads concurrently
+gpr_mpscq_node* gpr_locked_mpscq_try_pop(gpr_locked_mpscq* q);
+
+// Pop a node.  Returns NULL only if the queue was empty at some point after
+// calling this function
+gpr_mpscq_node* gpr_locked_mpscq_pop(gpr_locked_mpscq* q);
+
+#endif /* GRPC_CORE_LIB_GPR_MPSCQ_H */