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[SR-7582] Dispatch as a synchronisation mechanism fails TSan on Linux #655

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weissi opened this issue May 2, 2018 · 5 comments
Closed

[SR-7582] Dispatch as a synchronisation mechanism fails TSan on Linux #655

weissi opened this issue May 2, 2018 · 5 comments
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@yln
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bug libdispatch Linux

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@weissi
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weissi commented May 2, 2018

Previous ID SR-7582
Radar rdar://problem/40293937
Original Reporter @weissi
Type Bug
Status Resolved
Resolution Done

Attachment: Download

Additional Detail from JIRA
Votes 0
Component/s libdispatch
Labels Bug, Linux
Assignee @yln
Priority Medium

md5: 91cf68bf77060dfb66150dd2bc982357

Issue Description:

This easy program that should be thread synchronised just fine thanks to Dispatch fails TSan on Linux:

import Dispatch

var a: Int = 0
let q = DispatchQueue(label: "q")
q.async {
    a += 1
}

let aViaThread = q.sync { () -> Int in
    a += 1
    return a
}

print(aViaThread)

compiled with

swiftc -sanitize=thread test.swift

and then run with

./test

should raise no TSan (thread sanitizer) warnings on both Linux and macOS. It works just fine on Darwin but fails TSan on Linux:

$ ./test
==================
WARNING: ThreadSanitizer: data race (pid=1)
  Write of size 8 at 0x7b0c00000020 by main thread:
    #​0 free /code/workspace/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:621:3 (test+0xe461)
    #&#8203;1 _T08Dispatch0A5QueueC5asyncyAA0A5GroupCSg5group_AA0A3QoSV3qosAA0A13WorkItemFlagsV5flagsyyXB7executetF <null> (libdispatch.so+0x3c4ef)
    #&#8203;2 __libc_start_main <null> (libc.so.6+0x21ec4)

  Previous read of size 8 at 0x7b0c00000020 by thread T1:
    #&#8203;0 _T0Ieg_IeyB_TR <null> (test+0xbe59)
    #&#8203;1 _dispatch_call_block_and_release <null> (libdispatch.so+0x4d566)

  Thread T1 (tid=8, running) created by main thread at:
    #&#8203;0 pthread_create /code/workspace/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:889:3 (test+0xf9e3)
    #&#8203;1 _dispatch_global_queue_poke_slow <null> (libdispatch.so+0x59665)
    #&#8203;2 __libc_start_main <null> (libc.so.6+0x21ec4)

SUMMARY: ThreadSanitizer: data race (/usr/lib/swift/linux/libdispatch.so+0x3c4ef) in _T08Dispatch0A5QueueC5asyncyAA0A5GroupCSg5group_AA0A3QoSV3qosAA0A13WorkItemFlagsV5flagsyyXB7executetF
==================
==================
WARNING: ThreadSanitizer: data race (pid=1)
  Write of size 8 at 0x7b0c00000028 by main thread:
    #&#8203;0 free /code/workspace/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:621:3 (test+0xe461)
    #&#8203;1 _T08Dispatch0A5QueueC5asyncyAA0A5GroupCSg5group_AA0A3QoSV3qosAA0A13WorkItemFlagsV5flagsyyXB7executetF <null> (libdispatch.so+0x3c4ef)
    #&#8203;2 __libc_start_main <null> (libc.so.6+0x21ec4)

  Previous read of size 8 at 0x7b0c00000028 by thread T1:
    #&#8203;0 _T0Ieg_IeyB_TR <null> (test+0xbe71)
    #&#8203;1 _dispatch_call_block_and_release <null> (libdispatch.so+0x4d566)

  Thread T1 (tid=8, running) created by main thread at:
    #&#8203;0 pthread_create /code/workspace/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:889:3 (test+0xf9e3)
    #&#8203;1 _dispatch_global_queue_poke_slow <null> (libdispatch.so+0x59665)
    #&#8203;2 __libc_start_main <null> (libc.so.6+0x21ec4)

SUMMARY: ThreadSanitizer: data race (/usr/lib/swift/linux/libdispatch.so+0x3c4ef) in _T08Dispatch0A5QueueC5asyncyAA0A5GroupCSg5group_AA0A3QoSV3qosAA0A13WorkItemFlagsV5flagsyyXB7executetF
==================
==================
WARNING: ThreadSanitizer: Swift access race (pid=1)
  Modifying access of Swift variable at 0x5569bb345c88 by main thread:
    #&#8203;0 _T04testSiycfU0_ <null> (test+0xbf95)
    #&#8203;1 _T0Sis5Error_pIgdzo_SisAA_pIgrzo_TR <null> (test+0xc07d)
    #&#8203;2 _T0Sis5Error_pIgdzo_SisAA_pIgrzo_TRTA <null> (test+0xc25e)
    #&#8203;3 _T08Dispatch0A5QueueC11_syncHelper33_F417D752D2C4E9330E1C700411CE0C6ALLxyyycc2fn_xyKc7executexs5Error_pKc6rescuetKlFyxyKccfU_yycfU_ <null> (libdispatch.so+0x3c73b)
    #&#8203;4 __libc_start_main <null> (libc.so.6+0x21ec4)

  Previous write of size 8 at 0x5569bb345c88 by thread T1:
    #&#8203;0 _T04testyycfU_ <null> (test+0xbe08)
    #&#8203;1 _T0Ieg_IeyB_TR <null> (test+0xbe90)
    #&#8203;2 _dispatch_call_block_and_release <null> (libdispatch.so+0x4d566)

  Location is global '_T04test1aSivp' of size 8 at 0x5569bb345c88 (test+0x0000000b1c88)

  Thread T1 (tid=8, running) created by main thread at:
    #&#8203;0 pthread_create /code/workspace/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:889:3 (test+0xf9e3)
    #&#8203;1 _dispatch_global_queue_poke_slow <null> (libdispatch.so+0x59665)
    #&#8203;2 __libc_start_main <null> (libc.so.6+0x21ec4)

SUMMARY: ThreadSanitizer: Swift access race (/tmp/test+0xbf95) in _T04testSiycfU0_
==================
2
ThreadSanitizer: reported 3 warnings

environment: Swift 4.1 release
@weissi
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weissi commented May 6, 2018

CC phabouzit (JIRA User) and @kubamracek

@weissi
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weissi commented May 13, 2018

CC das (JIRA User)

@weissi
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weissi commented May 16, 2018

@swift-ci create

@weissi
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weissi commented Aug 27, 2019

@yln this should be fixed, right?

@yln
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yln commented Aug 27, 2019

Yes, this is fixed on Linux starting with Swift 5.1.

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
@shahmishal shahmishal transferred this issue from apple/swift May 5, 2022
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