40 lines
1.4 KiB
Go
40 lines
1.4 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// waiterUnlock is called from g0, so when the race detector is enabled,
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// waiterUnlock must be implemented in assembly since no race context is
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// available.
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//
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// +build !race
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// +build !amd64,!arm64
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package syncevent
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import (
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"sync/atomic"
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"unsafe"
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)
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// waiterUnlock is the "unlock function" passed to runtime.gopark by
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// Waiter.Wait*. wg is &Waiter.g, and g is a pointer to the calling runtime.g.
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// waiterUnlock returns true if Waiter.Wait should sleep and false if sleeping
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// should be aborted.
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//
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//go:nosplit
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func waiterUnlock(ptr unsafe.Pointer, wg *unsafe.Pointer) bool {
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// The only way this CAS can fail is if a call to Waiter.NotifyPending()
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// has replaced *wg with nil, in which case we should not sleep.
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return atomic.CompareAndSwapPointer(wg, (unsafe.Pointer)(&preparingG), ptr)
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}
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