Fix data race in BucketedBytes pool
#4792
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Previous test didn't detect the data race: we copied the bytes header to
the bytes.Buffer so when appending to the slice we were not modifying
the original one.
However, the usage of this in bucketChunkReader.save() actually modifies
the referenced slice, so the test was modified to test that it can be
done safely.
The race condition happened because we were reading the referenced slice
capacity after putting it back to the pool, when someone else might
already retrieved and modified it.
Before modifying the implementation, this was the data race reported:
==================
WARNING: DATA RACE
Read at 0x00c0000bc900 by goroutine 36:
github.com/thanos-io/thanos/pkg/pool.(*BucketedBytes).Put()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool.go:124 +0x1f9
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet.func1()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:108 +0xfa
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet·dwrap·3()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:119 +0x65
Previous write at 0x00c0000bc900 by goroutine 27:
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet.func1()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:94 +0x1fa
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet·dwrap·3()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:119 +0x65
Goroutine 36 (running) created at:
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:119 +0x257
testing.tRunner()
/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1259 +0x22f
testing.(*T).Run·dwrap·21()
1 Fix data race in BucketedBytes pool
/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1306 +0x47
Goroutine 27 (running) created at:
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:119 +0x257
testing.tRunner()
/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1259 +0x22f
testing.(*T).Run·dwrap·21()
/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1306 +0x47
==================
Signed-off-by: Oleg Zaytsev <[email protected]>
Signed-off-by: Oleg Zaytsev <[email protected]>
|
Marking this change as not relevant for the end user because the data race is really minor and can't cause data corruption. |
pracucci
previously approved these changes
Oct 20, 2021
Signed-off-by: Oleg Zaytsev <[email protected]>
GiedriusS
approved these changes
Oct 20, 2021
bwplotka
approved these changes
Oct 20, 2021
GiedriusS
pushed a commit
to GiedriusS/thanos
that referenced
this pull request
Oct 22, 2021
* Fix data race in BucketedBytes pool
Previous test didn't detect the data race: we copied the bytes header to
the bytes.Buffer so when appending to the slice we were not modifying
the original one.
However, the usage of this in bucketChunkReader.save() actually modifies
the referenced slice, so the test was modified to test that it can be
done safely.
The race condition happened because we were reading the referenced slice
capacity after putting it back to the pool, when someone else might
already retrieved and modified it.
Before modifying the implementation, this was the data race reported:
==================
WARNING: DATA RACE
Read at 0x00c0000bc900 by goroutine 36:
github.com/thanos-io/thanos/pkg/pool.(*BucketedBytes).Put()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool.go:124 +0x1f9
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet.func1()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:108 +0xfa
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet·dwrap·3()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:119 +0x65
Previous write at 0x00c0000bc900 by goroutine 27:
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet.func1()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:94 +0x1fa
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet·dwrap·3()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:119 +0x65
Goroutine 36 (running) created at:
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:119 +0x257
testing.tRunner()
/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1259 +0x22f
testing.(*T).Run·dwrap·21()
1 Fix data race in BucketedBytes pool
/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1306 +0x47
Goroutine 27 (running) created at:
github.com/thanos-io/thanos/pkg/pool.TestRacePutGet()
/Users/oleg/w/github.com/thanos-io/thanos/pkg/pool/pool_test.go:119 +0x257
testing.tRunner()
/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1259 +0x22f
testing.(*T).Run·dwrap·21()
/usr/local/Cellar/go/1.17/libexec/src/testing/testing.go:1306 +0x47
==================
Signed-off-by: Oleg Zaytsev <[email protected]>
* Update CHANGELOG.md
Signed-off-by: Oleg Zaytsev <[email protected]>
* goimports fix
Signed-off-by: Oleg Zaytsev <[email protected]>
Signed-off-by: Giedrius Statkevičius <[email protected]>
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Changes
Previous test didn't detect the data race: we copied the bytes header to the bytes.Buffer so when appending to the slice we were not modifying the original one.
However, the usage of this in
bucketChunkReader.save()actually modifies the referenced slice, so the test was modified to test that it can be done safely.The race condition happened because we were reading the referenced slice capacity after putting it back to the pool, when someone else might already retrieved and modified it.
Verification
The test was updated to match the real-life usage of the pool.
Before modifying the implementation, this was the data race reported by the updated test: