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expression: fix data race of rand function #11168

Merged
merged 3 commits into from
Jul 10, 2019
Merged

expression: fix data race of rand function #11168

merged 3 commits into from
Jul 10, 2019

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alivxxx
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@alivxxx alivxxx commented Jul 10, 2019

What problem does this PR solve? 

WARNING: DATA RACE
Read at 0x00c000345508 by goroutine 81:
  math/rand.(*rngSource).Int63()
      /usr/lib/go/src/math/rand/rng.go:244 +0x8f
  github.com/pingcap/tidb/expression.(*builtinRandSig).evalReal()
      /usr/lib/go/src/math/rand/rand.go:85 +0x7a
  github.com/pingcap/tidb/expression.(*ScalarFunction).EvalReal()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/scalar_function.go:239 +0x73
  github.com/pingcap/tidb/expression.executeToReal()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/chunk_executor.go:143 +0x79
  github.com/pingcap/tidb/expression.evalOneColumn()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/chunk_executor.go:75 +0x2c0
  github.com/pingcap/tidb/expression.(*defaultEvaluator).run()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/evaluator.go:47 +0x664
  github.com/pingcap/tidb/expression.(*EvaluatorSuite).Run()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/evaluator.go:113 +0x113
  github.com/pingcap/tidb/executor.(*projectionWorker).run()
      /home/aliv/go/src/github.com/pingcap/tidb/executor/projection.go:356 +0x246

Previous write at 0x00c000345508 by goroutine 116:
  math/rand.(*rngSource).Int63()
      /usr/lib/go/src/math/rand/rng.go:244 +0xab
  github.com/pingcap/tidb/expression.(*builtinRandSig).evalReal()
      /usr/lib/go/src/math/rand/rand.go:85 +0x7a
  github.com/pingcap/tidb/expression.(*ScalarFunction).EvalReal()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/scalar_function.go:239 +0x73
  github.com/pingcap/tidb/expression.executeToReal()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/chunk_executor.go:143 +0x79
  github.com/pingcap/tidb/expression.evalOneColumn()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/chunk_executor.go:75 +0x2c0
  github.com/pingcap/tidb/expression.(*defaultEvaluator).run()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/evaluator.go:47 +0x664
  github.com/pingcap/tidb/expression.(*EvaluatorSuite).Run()
      /home/aliv/go/src/github.com/pingcap/tidb/expression/evaluator.go:113 +0x113
  github.com/pingcap/tidb/executor.(*projectionWorker).run()
      /home/aliv/go/src/github.com/pingcap/tidb/executor/projection.go:356 +0x246

What is changed and how it works?

Add a mutex for rand to prevent data race.

Check List

Tests

  • Unit test

Code changes

  • Has exported function/method change

Side effects

  • None

Related changes

  • Need to cherry-pick to the release branch

winkyao
winkyao reviewed Jul 10, 2019
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LGTM

winoros
winoros reviewed Jul 10, 2019
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lgtm

@alivxxx
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alivxxx commented Jul 10, 2019

/run-all-tests

@alivxxx alivxxx added needs-cherry-pick-2.1 status/LGT2 Indicates that a PR has LGTM 2. labels Jul 10, 2019
XuHuaiyu
XuHuaiyu reviewed Jul 10, 2019
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expression/builtin_math.go
@@ -988,19 +989,23 @@ func (c *randFunctionClass) getFunction(ctx sessionctx.Context, args []Expressio

type builtinRandSig struct {
baseBuiltinFunc
mu *sync.Mutex
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All the projectWorkers will battle for this Mutex?

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Yes, and this is the only way to make it correct.

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codecov bot commented Jul 10, 2019

Codecov Report

Merging #11168 into master will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master     #11168   +/-   ##
===========================================
  Coverage   81.1123%   81.1123%           
===========================================
  Files           423        423           
  Lines         90382      90382           
===========================================
  Hits          73311      73311           
  Misses        11788      11788           
  Partials       5283       5283

@alivxxx
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alivxxx commented Jul 10, 2019

/run-integration-ddl-test

@alivxxx alivxxx merged commit f409f0b into pingcap:master Jul 10, 2019
@alivxxx alivxxx deleted the data-race branch July 10, 2019 09:39
@alivxxx alivxxx changed the title expressio: fix data race of rand function expression: fix data race of rand function Jul 10, 2019
alivxxx added a commit to alivxxx/tidb that referenced this pull request Jul 10, 2019
@alivxxx
expression: fix data race of rand function (pingcap#11168)
5eb9065
@alivxxx alivxxx mentioned this pull request Jul 10, 2019
Merged
alivxxx added a commit to alivxxx/tidb that referenced this pull request Jul 10, 2019
@alivxxx
expression: fix data race of rand function (pingcap#11168)
878730d
@alivxxx alivxxx mentioned this pull request Jul 10, 2019
Merged
ngaut pushed a commit that referenced this pull request Jul 11, 2019
@alivxxx @ngaut
expression: fix data race of rand function (#11168) (#11169)
d1848b0
zz-jason pushed a commit that referenced this pull request Jul 11, 2019
@alivxxx @zz-jason
expression: fix data race of rand function (#11168) (#11170)
7cdce5b
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Reviewers

@XuHuaiyu XuHuaiyu XuHuaiyu left review comments

@winkyao winkyao winkyao left review comments

@winoros winoros winoros approved these changes

@zz-jason zz-jason Awaiting requested review from zz-jason

@qw4990 qw4990 Awaiting requested review from qw4990

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@alivxxx @winkyao @winoros @XuHuaiyu