6de410a0aa
To avoid this issue with refCounter refactor the code such that - locker() always increases refCount upon success - unlocker() always decrements refCount upon success (as a special case removes the resource if the refCount is zero) By these two assumptions we are able to see that we are never granted two write lockers in any situation. Thanks to @vcabbage for writing a nice reproducer.
101 lines
2.9 KiB
Go
101 lines
2.9 KiB
Go
/*
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* MinIO Cloud Storage, (C) 2016 MinIO, Inc.
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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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*/
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package cmd
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import (
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"context"
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"runtime"
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"testing"
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"time"
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)
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// WARNING:
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//
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// Expected source line number is hard coded, 31, in the
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// following test. Adding new code before this test or changing its
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// position will cause the line number to change and the test to FAIL
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// Tests getSource().
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func TestGetSource(t *testing.T) {
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currentSource := func() string { return getSource(2) }
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gotSource := currentSource()
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// Hard coded line number, 34, in the "expectedSource" value
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expectedSource := "[namespace-lock_test.go:34:TestGetSource()]"
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if gotSource != expectedSource {
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t.Errorf("expected : %s, got : %s", expectedSource, gotSource)
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}
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}
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// Test lock race
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func TestNSLockRace(t *testing.T) {
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ctx := context.Background()
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for i := 0; i < 10000; i++ {
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nsLk := newNSLock(false)
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// lk1; ref=1
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if !nsLk.lock(ctx, "volume", "path", "source", "opsID", false, time.Second) {
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t.Fatal("failed to acquire lock")
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}
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// lk2
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lk2ch := make(chan struct{})
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go func() {
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defer close(lk2ch)
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nsLk.lock(ctx, "volume", "path", "source", "opsID", false, 1*time.Millisecond)
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}()
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time.Sleep(1 * time.Millisecond) // wait for goroutine to advance; ref=2
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// Unlock the 1st lock; ref=1 after this line
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nsLk.unlock("volume", "path", false)
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// Taking another lockMapMutex here allows queuing up additional lockers. This should
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// not be required but makes reproduction much easier.
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nsLk.lockMapMutex.Lock()
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// lk3 blocks.
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lk3ch := make(chan bool)
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go func() {
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lk3ch <- nsLk.lock(ctx, "volume", "path", "source", "opsID", false, 0)
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}()
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// lk4, blocks.
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lk4ch := make(chan bool)
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go func() {
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lk4ch <- nsLk.lock(ctx, "volume", "path", "source", "opsID", false, 0)
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}()
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runtime.Gosched()
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// unlock the manual lock
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nsLk.lockMapMutex.Unlock()
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// To trigger the race:
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// 1) lk3 or lk4 need to advance and increment the ref on the existing resource,
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// successfully acquiring the lock.
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// 2) lk2 then needs to advance and remove the resource from lockMap.
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// 3) lk3 or lk4 (whichever didn't execute in step 1) then executes and creates
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// a new entry in lockMap and acquires a lock for the same resource.
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<-lk2ch
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lk3ok := <-lk3ch
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lk4ok := <-lk4ch
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if lk3ok && lk4ok {
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t.Fatalf("multiple locks acquired; iteration=%d, lk3=%t, lk4=%t", i, lk3ok, lk4ok)
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}
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}
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}
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