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authorkevin.xu <cming.xu@gmail.com>2020-04-27 21:51:31 +0800
committerGitHub <noreply@github.com>2020-04-27 21:51:31 +0800
commite896ca54db67524afc20b644d43c72185e72dc0e (patch)
tree2a16f3a62a5cafd098f1f028c621f1b655589d69 /pkg/syncevent/waiter_noasm_unsafe.go
parent1f19624fa127d7d59cabe29593cc80b7fe6c81f8 (diff)
parent3c67754663f424f2ebbc0ff2a4c80e30618d5355 (diff)
Merge pull request #1 from google/master
catch up
Diffstat (limited to 'pkg/syncevent/waiter_noasm_unsafe.go')
-rw-r--r--pkg/syncevent/waiter_noasm_unsafe.go39
1 files changed, 39 insertions, 0 deletions
diff --git a/pkg/syncevent/waiter_noasm_unsafe.go b/pkg/syncevent/waiter_noasm_unsafe.go
new file mode 100644
index 000000000..1c4b0e39a
--- /dev/null
+++ b/pkg/syncevent/waiter_noasm_unsafe.go
@@ -0,0 +1,39 @@
+// Copyright 2020 The gVisor 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.
+
+// waiterUnlock is called from g0, so when the race detector is enabled,
+// waiterUnlock must be implemented in assembly since no race context is
+// available.
+//
+// +build !race
+// +build !amd64,!arm64
+
+package syncevent
+
+import (
+ "sync/atomic"
+ "unsafe"
+)
+
+// waiterUnlock is the "unlock function" passed to runtime.gopark by
+// Waiter.Wait*. wg is &Waiter.g, and g is a pointer to the calling runtime.g.
+// waiterUnlock returns true if Waiter.Wait should sleep and false if sleeping
+// should be aborted.
+//
+//go:nosplit
+func waiterUnlock(g unsafe.Pointer, wg *unsafe.Pointer) bool {
+ // The only way this CAS can fail is if a call to Waiter.NotifyPending()
+ // has replaced *wg with nil, in which case we should not sleep.
+ return atomic.CompareAndSwapPointer(wg, (unsafe.Pointer)(&preparingG), g)
+}