From 8c8c6c27552f8554ba014c34d684cb90538ef65b Mon Sep 17 00:00:00 2001 From: Luke Shumaker Date: Tue, 28 Feb 2023 14:05:27 -0700 Subject: Move files around [ci-skip] --- lib/btrfsutil/nestedlock.go | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 lib/btrfsutil/nestedlock.go (limited to 'lib/btrfsutil/nestedlock.go') diff --git a/lib/btrfsutil/nestedlock.go b/lib/btrfsutil/nestedlock.go new file mode 100644 index 0000000..c1ffa18 --- /dev/null +++ b/lib/btrfsutil/nestedlock.go @@ -0,0 +1,45 @@ +// Copyright (C) 2023 Luke Shumaker +// +// SPDX-License-Identifier: GPL-2.0-or-later + +package btrees + +import ( + "context" + "sync" +) + +// A nestedMutex is like a sync.Mutex, but while it is locked by call +// 'A', may be simultaneously locked by subsequent calls if the +// subsequent calls use a Context descended from the one returned by +// the 'A' call to .Lock(). +type nestedMutex struct { + inner sync.Mutex + depth int +} + +type nestedMutexCtxKey struct{} + +// Lock locks the mutex. It is invalid to use a Context returned from +// Lock in a different goroutine than the one it was created in. It +// is invalid to use a Context returned from Lock after the mutex has +// subsequently become unlocked. +func (m *nestedMutex) Lock(ctx context.Context) context.Context { + if other, ok := ctx.Value(nestedMutexCtxKey{}).(*nestedMutex); ok && other == m { + m.depth++ + return ctx + } + m.inner.Lock() + return context.WithValue(ctx, nestedMutexCtxKey{}, m) +} + +// Unlock unlocks the mutex. It is invalid to call Unlock if the +// mutex is not already locked. It is invalid to call Unlock from +// multiple goroutines simultaneously. +func (m *nestedMutex) Unlock() { + if m.depth > 0 { + m.depth-- + } else { + m.inner.Unlock() + } +} -- cgit v1.2.3-54-g00ecf