[swift-users] Is this really a race condition?
Dave Abrahams
dabrahams at apple.com
Wed Mar 1 16:55:56 CST 2017
on Wed Mar 01 2017, Edward Connell <swift-users-AT-swift.org> wrote:
> The thread sanitizer on Linux is reporting that I have race conditions in
> libswiftcore.
The only one we currently know about that's actually in libswiftcore is
the one addressed by https://github.com/apple/swift/pull/7183
> I eliminated enough code down to this trivial example. Is there really
> a race condition here or are these bogus errors?
>
> let count = 1000
> var items = [[UInt8]?](repeating: nil, count: count)
>
> DispatchQueue.concurrentPerform(iterations: count) {
> items[$0] = [UInt8](repeating: 7, count: 10)
> }
>
> My real scenario is retrieving data asynchronously, so I just threw in a
> buffer assignment.
>
> Thanks, Ed
>
> ==================
> WARNING: ThreadSanitizer: data race (pid=30720)
> Read of size 8 at 0x7d9000008028 by thread T16:
> #0 memcpy <null> (libtsan.so.0+0x00000002617a)
> #1 _TwCcOs31_ClosedRangeIndexRepresentation <null>
> (libswiftCore.so+0x00000027e0fa)
>
> Previous write of size 8 at 0x7d9000008028 by main thread:
> #0 memcpy <null> (libtsan.so.0+0x00000002617a)
> #1 _TwCcOs31_ClosedRangeIndexRepresentation <null>
> (libswiftCore.so+0x00000027e0fa)
>
> Location is heap block of size 8032 at 0x7d9000008000 allocated by main
> thread:
> #0 malloc <null> (libtsan.so.0+0x0000000254a3)
> #1 swift_slowAlloc <null> (libswiftCore.so+0x0000002ee3e5)
>
> Thread T16 (tid=30917, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 manager_workqueue_additem
> /home/buildnode/disk2/workspace/oss-swift-3.0-package-linux-ubuntu-16_04/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:815
> (libdispatch.so+0x00000007c6b1)
>
> SUMMARY: ThreadSanitizer: data race ??:0 memcpy
> ==================
> ==================
> WARNING: ThreadSanitizer: data race (pid=30720)
> Write of size 8 at 0x7d0c00015d80 by thread T16:
> #0 free <null> (libtsan.so.0+0x000000025819)
> #1 _TwXxOs31_ClosedRangeIndexRepresentation <null>
> (libswiftCore.so+0x00000027e071)
>
> Previous write of size 8 at 0x7d0c00015d80 by main thread:
> #0 malloc <null> (libtsan.so.0+0x0000000254a3)
> #1 swift_slowAlloc <null> (libswiftCore.so+0x0000002ee3e5)
>
> Thread T16 (tid=30917, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 manager_workqueue_additem
> /home/buildnode/disk2/workspace/oss-swift-3.0-package-linux-ubuntu-16_04/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:815
> (libdispatch.so+0x00000007c6b1)
>
> SUMMARY: ThreadSanitizer: data race ??:0 __interceptor_free
> ==================
> ==================
> WARNING: ThreadSanitizer: data race (pid=30720)
> Write of size 8 at 0x7d900000a028 by thread T20:
> #0 free <null> (libtsan.so.0+0x000000025819)
> #1 _TZFSa11_copyBufferfRGVs22_ContiguousArrayBufferx_T_ <null>
> (libswiftCore.so+0x00000010884e)
>
> Previous read of size 8 at 0x7d900000a028 by thread T17:
> #0 memcpy <null> (libtsan.so.0+0x00000002617a)
> #1 _TwCcOs31_ClosedRangeIndexRepresentation <null>
> (libswiftCore.so+0x00000027e0fa)
>
> Thread T20 (tid=30921, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 manager_workqueue_additem
> /home/buildnode/disk2/workspace/oss-swift-3.0-package-linux-ubuntu-16_04/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:815
> (libdispatch.so+0x00000007c6b1)
>
> Thread T17 (tid=30918, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 manager_workqueue_additem
> /home/buildnode/disk2/workspace/oss-swift-3.0-package-linux-ubuntu-16_04/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:815
> (libdispatch.so+0x00000007c6b1)
>
> SUMMARY: ThreadSanitizer: data race ??:0 __interceptor_free
> ==================
> ==================
> WARNING: ThreadSanitizer: data race (pid=30720)
> Read of size 8 at 0x7d9000006028 by thread T23:
> #0 memcpy <null> (libtsan.so.0+0x00000002617a)
> #1 _TwCcOs31_ClosedRangeIndexRepresentation <null>
> (libswiftCore.so+0x00000027e0fa)
>
> Previous write of size 8 at 0x7d9000006028 by main thread:
> #0 malloc <null> (libtsan.so.0+0x0000000254a3)
> #1 swift_slowAlloc <null> (libswiftCore.so+0x0000002ee3e5)
>
> Location is heap block of size 8032 at 0x7d9000006000 allocated by main
> thread:
> #0 malloc <null> (libtsan.so.0+0x0000000254a3)
> #1 swift_slowAlloc <null> (libswiftCore.so+0x0000002ee3e5)
>
> Thread T23 (tid=30924, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 manager_workqueue_additem
> /home/buildnode/disk2/workspace/oss-swift-3.0-package-linux-ubuntu-16_04/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:815
> (libdispatch.so+0x00000007c6b1)
>
> SUMMARY: ThreadSanitizer: data race ??:0 memcpy
> ==================
> ==================
> WARNING: ThreadSanitizer: data race (pid=30720)
> Write of size 8 at 0x7d900002e000 by thread T19:
> #0 free <null> (libtsan.so.0+0x000000025819)
> #1 _TZFSa11_copyBufferfRGVs22_ContiguousArrayBufferx_T_ <null>
> (libswiftCore.so+0x000000108859)
>
> Previous write of size 8 at 0x7d900002e000 by thread T20:
> #0 malloc <null> (libtsan.so.0+0x0000000254a3)
> #1 swift_slowAlloc <null> (libswiftCore.so+0x0000002ee3e5)
>
> Thread T19 (tid=30920, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 manager_workqueue_additem
> /home/buildnode/disk2/workspace/oss-swift-3.0-package-linux-ubuntu-16_04/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:815
> (libdispatch.so+0x00000007c6b1)
>
> Thread T20 (tid=30921, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 manager_workqueue_additem
> /home/buildnode/disk2/workspace/oss-swift-3.0-package-linux-ubuntu-16_04/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:815
> (libdispatch.so+0x00000007c6b1)
>
> SUMMARY: ThreadSanitizer: data race ??:0 __interceptor_free
> ==================
> ==================
> WARNING: ThreadSanitizer: data race (pid=30720)
> Write of size 8 at 0x7d9000004000 by thread T17:
> #0 free <null> (libtsan.so.0+0x000000025819)
> #1 _TZFSa11_copyBufferfRGVs22_ContiguousArrayBufferx_T_ <null>
> (libswiftCore.so+0x00000010884e)
>
> Previous write of size 8 at 0x7d9000004000 by main thread:
> #0 malloc <null> (libtsan.so.0+0x0000000254a3)
> #1 swift_slowAlloc <null> (libswiftCore.so+0x0000002ee3e5)
>
> Thread T17 (tid=30918, running) created by main thread at:
> #0 pthread_create <null> (libtsan.so.0+0x000000027577)
> #1 manager_workqueue_additem
> /home/buildnode/disk2/workspace/oss-swift-3.0-package-linux-ubuntu-16_04/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:815
> (libdispatch.so+0x00000007c6b1)
>
> SUMMARY: ThreadSanitizer: data race ??:0 __interceptor_free
> ==================
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
--
-Dave
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