[SR-4647] foundation: TestFoundation/TestNSURLSession.swift test sometimes fails with a timeout

[eeckstein]

Previous ID	SR-4647
Radar	None
Original Reporter	@eeckstein
Type	Bug

Additional Detail from JIRA

Votes	0
Component/s	libdispatch
Labels	Bug
Assignee	None
Priority	Medium

md5: 4a1394511243d61e45bb58adf2ad7e6d

Issue Description:

TestFoundation/TestNSURLSession.swift:254: error: TestURLSession.test_downloadTaskWithURLAndHandler : Asynchronous wait failed - Exceeded timeout of 12.0 seconds, with unfulfilled expectations: download task with handler

[pushkarnk]

Reproduced a similar hang locally after a lot of patience. These are the threads:

* thread #&#8203;1: tid = 8106, 0x00007ffff5d08c21 libc.so.6`__GI_ppoll(fds=0x00007fffffffcf48, nfds=1, timeout=<unavailable>, sigmask=0x0000000000000000) + 145 at ppoll.c:50, name = 'TestFoundation', stop reason = signal SIGSTOP
  * frame #&#8203;0: 0x00007ffff5d08c21 libc.so.6`__GI_ppoll(fds=0x00007fffffffcf48, nfds=1, timeout=<unavailable>, sigmask=0x0000000000000000) + 145 at ppoll.c:50
    frame #&#8203;1: 0x00007ffff713aa31 libFoundation.so`__CFRunLoopServiceFileDescriptors + 225
    frame #&#8203;2: 0x00007ffff7136807 libFoundation.so`__CFRunLoopRun + 1095
    frame #&#8203;3: 0x00007ffff7136179 libFoundation.so`CFRunLoopRunSpecific + 489
    frame #&#8203;4: 0x00007ffff74046ce libFoundation.so`_T010Foundation7RunLoopC3runyAA4DateV5until_tF + 382
    frame #&#8203;5: 0x00007ffff7f46956 libXCTest.so`_T06XCTest0A4CaseC19waitForExpectationsySd7timeout_s12StaticStringV4fileSu4liney10Foundation7NSErrorCSgcSg7handlertF + 502
    frame #&#8203;6: 0x00000000006cb5f6 TestFoundation`_T014TestFoundation0A10URLSessionC37test_dataTaskWithURLCompletionHandleryyF + 1510
    frame #&#8203;7: 0x00000000006dd318 TestFoundation`_T0TA.391 + 24
    frame #&#8203;8: 0x0000000000444b26 TestFoundation`_T0s5Error_pIxzo_ytytsAA_pIxirzo_TR + 22
    frame #&#8203;9: 0x00000000006dd43b TestFoundation`_T0s5Error_pIxzo_ytytsAA_pIxirzo_TRTA + 91
    frame #&#8203;10: 0x00007ffff7f663bf libXCTest.so`_T0ytyts5Error_pIxirzo_sAA_pIxzo_TRTA + 47
    frame #&#8203;11: 0x00007ffff7f5a0d1 libXCTest.so`_T06XCTest4test33_3BE257A46ADB477C7BF2D39968B39F9DLLyAA0A4CaseCKcyyKcxcAERbzlFyAEKcfU_Tf4gg_n + 81
    frame #&#8203;12: 0x00007ffff7f662df libXCTest.so`_T06XCTest4test33_3BE257A46ADB477C7BF2D39968B39F9DLLyAA0A4CaseCKcyyKcxcAERbzlFyAEKcfU_TA + 79
    frame #&#8203;13: 0x00007ffff7f66f89 libXCTest.so`_T06XCTest4test33_3BE257A46ADB477C7BF2D39968B39F9DLLyAA0A4CaseCKcyyKcxcAERbzlFyAEKcfU_TA.190 + 9
    frame #&#8203;14: 0x00007ffff7f6623b libXCTest.so`_T06XCTest0A4CaseCs5Error_pIxxzo_ACytsAD_pIxirzo_TRTA + 59
    frame #&#8203;15: 0x00007ffff7f67019 libXCTest.so`_T06XCTest0A4CaseCs5Error_pIxxzo_ACytsAD_pIxirzo_TRTA.183 + 9
    frame #&#8203;16: 0x00007ffff7f5c110 libXCTest.so`_T06XCTest0A4CaseCyts5Error_pIxirzo_ACsAD_pIxxzo_TRTA + 64
    frame #&#8203;17: 0x00007ffff7f40956 libXCTest.so`_T06XCTest0A4CaseC10invokeTestyyF + 102
    frame #&#8203;18: 0x00007ffff7f58285 libXCTest.so`_T06XCTest0A4CaseC7performyAA0A3RunCFTf4gn_n + 309
    frame #&#8203;19: 0x00007ffff7f4083e libXCTest.so`_T06XCTest0A4CaseC7performyAA0A3RunCF + 14
    frame #&#8203;20: 0x00007ffff7f3ea55 libXCTest.so`_T06XCTestAAC3runyyF + 549
    frame #&#8203;21: 0x00007ffff7f586ce libXCTest.so`_T06XCTest0A5SuiteC7performyAA0A3RunCFTf4gn_n + 766
    frame #&#8203;22: 0x00007ffff7f58aa1 libXCTest.so`_T06XCTest0A5SuiteC7performyAA0A3RunCFTf4gn_n + 1745
    frame #&#8203;23: 0x00007ffff7f58aa1 libXCTest.so`_T06XCTest0A5SuiteC7performyAA0A3RunCFTf4gn_n + 1745
    frame #&#8203;24: 0x00007ffff7f42e2c libXCTest.so`_T06XCTest7XCTMains5NeverOSayAA0A4CaseCm04testD5Class_SaySS_yAFKctG8allTeststGF + 4556
    frame #&#8203;25: 0x0000000000435955 TestFoundation`main + 7349
    frame #&#8203;26: 0x00007ffff5c2e830 libc.so.6`__libc_start_main(main=(TestFoundation`main), argc=1, argv=0x00007fffffffe468, init=<unavailable>, fini=<unavailable>, rtld_fini=<unavailable>, stack_end=0x00007fffffffe458) + 240 at libc-start.c:291
    frame #&#8203;27: 0x0000000000433bb9 TestFoundation`_start + 41

  thread #&#8203;2: tid = 8155, 0x00007ffff6c8ea15 libpthread.so.0`do_futex_wait + 69, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff6c8ea15 libpthread.so.0`do_futex_wait + 69
    frame #&#8203;1: 0x00007ffff6c8eadf libpthread.so.0`__new_sem_wait_slow + 95
    frame #&#8203;2: 0x00007ffff6c8eb92 libpthread.so.0`sem_timedwait + 66
    frame #&#8203;3: 0x00007ffff7ef6afb libdispatch.so`manager_main(unused=<unavailable>) + 2283 at manager.c:620
    frame #&#8203;4: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;5: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

  thread #&#8203;3: tid = 8156, 0x00007ffff6c8f76d libpthread.so.0`__GI_accept + 45, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff6c8f76d libpthread.so.0`__GI_accept + 45
    frame #&#8203;1: 0x0000000000437c2b TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_s5Int32VyXKfu_ + 123
    frame #&#8203;2: 0x0000000000441839 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_s5Int32VyXKfu_TA + 73
    frame #&#8203;3: 0x00000000004361a0 TestFoundation`_T014TestFoundation10_TCPSocketC7attempt33_AC276A005C0DEB782845E1C79EF92149LLs5Int32VSS_SS4fileSu4lineSbAGc5validAGyXKtKF + 144
    frame #&#8203;4: 0x0000000000437999 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_ + 409
    frame #&#8203;5: 0x0000000000437aef TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_TA + 95
    frame #&#8203;6: 0x0000000000437186 TestFoundation`_T0SpySC8sockaddrVGs5Error_pIxyzo_ACytsAD_pIxyrzo_TR + 22
    frame #&#8203;7: 0x0000000000437b9b TestFoundation`_T0SpySC8sockaddrVGs5Error_pIxyzo_ACytsAD_pIxyrzo_TRTA.13 + 91
    frame #&#8203;8: 0x00007ffff7aae937 libswiftCore.so`_T0SP17withMemoryReboundqd_0_qd__m2to_Si8capacityqd_0_SPyqd__GKctKr0_lF + 55
    frame #&#8203;9: 0x00007ffff7c7692f libswiftCore.so`_T0Sp17withMemoryReboundqd_0_qd__m2to_Si8capacityqd_0_Spyqd__GKctKr0_lF + 15
    frame #&#8203;10: 0x00000000004376c0 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKF + 512
    frame #&#8203;11: 0x000000000043ab07 TestFoundation`_T014TestFoundation11_HTTPServerC6listenyAA15ServerSemaphoreC6notify_tKF + 71
    frame #&#8203;12: 0x000000000043d63e TestFoundation`_T014TestFoundation0A16URLSessionServerC5startyAA0D9SemaphoreC7started_tKF + 94
    frame #&#8203;13: 0x00000000006c9f5d TestFoundation`_T014TestFoundation0A10URLSessionC9runServer33_F3FECA45EA2EBA0C2372DABFC6747FB7LLyAA0E9SemaphoreC4with_SdSg10startDelayAI04sendP0SiSg10bodyChunkstKF + 605
    frame #&#8203;14: 0x00000000006cb6f5 TestFoundation`_T014TestFoundation0A10URLSessionC37test_dataTaskWithURLCompletionHandleryyFyycfU_ + 133
    frame #&#8203;15: 0x00000000006d5a03 TestFoundation`_T014TestFoundation0A10URLSessionC37test_dataTaskWithURLCompletionHandleryyFyycfU_TA + 67
    frame #&#8203;16: 0x000000000043c1e9 TestFoundation`_T0Ix_IyB_TR + 41
    frame #&#8203;17: 0x00007ffff7ec8f37 libdispatch.so`_dispatch_call_block_and_release + 7
    frame #&#8203;18: 0x00007ffff7ed7455 libdispatch.so`_dispatch_root_queue_drain + 533
    frame #&#8203;19: 0x00007ffff7ef6f0f libdispatch.so`worker_main(unused=<unavailable>) + 207 at manager.c:506
    frame #&#8203;20: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;21: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

  thread #&#8203;4: tid = 8157, 0x00007ffff5d0e8e9 libc.so.6`syscall + 25 at syscall.S:38, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff5d0e8e9 libc.so.6`syscall + 25 at syscall.S:38
    frame #&#8203;1: 0x00007ffff7edfa09 libdispatch.so`_dispatch_thread_event_wait_slow + 57
    frame #&#8203;2: 0x00007ffff7ed6a38 libdispatch.so`_dispatch_sync_wait + 264
    frame #&#8203;3: 0x00007ffff7ee85ad libdispatch.so`_T08Dispatch0A5QueueC4syncxxyKc7execute_tKlF + 301
    frame #&#8203;4: 0x00007ffff74c30cb libFoundation.so`_T010Foundation14URLSessionTaskC19configureEasyHandle33_655ABFF49E18DABF12076554C1107FC4LLyAA10URLRequestV3for_tFTf4gn_n + 3931
    frame #&#8203;5: 0x00007ffff74c524d libFoundation.so`_T010Foundation14URLSessionTaskC16startNewTransfer33_655ABFF49E18DABF12076554C1107FC4LLyAA10URLRequestV4with_tFTf4gn_n + 2237
    frame #&#8203;6: 0x00007ffff74b56c8 libFoundation.so`_T010Foundation14URLSessionTaskC13performResume33_655ABFF49E18DABF12076554C1107FC4LLyyF + 104
    frame #&#8203;7: 0x00007ffff74cc009 libFoundation.so`_T010Foundation14URLSessionTaskC6resumeyyFyycfU_yycfU_TA + 9
    frame #&#8203;8: 0x00007ffff73b1d40 libFoundation.so`_T0Ix_IyB_TR + 32
    frame #&#8203;9: 0x00007ffff7ec8f37 libdispatch.so`_dispatch_call_block_and_release + 7
    frame #&#8203;10: 0x00007ffff7ed4c9d libdispatch.so`_dispatch_queue_serial_drain + 493
    frame #&#8203;11: 0x00007ffff7ed5650 libdispatch.so`_dispatch_queue_invoke + 976
    frame #&#8203;12: 0x00007ffff7ed73b4 libdispatch.so`_dispatch_root_queue_drain + 372
    frame #&#8203;13: 0x00007ffff7ef5f68 libdispatch.so`overcommit_worker_main(unused=<unavailable>) + 264 at manager.c:315
    frame #&#8203;14: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;15: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

  thread #&#8203;5: tid = 8158, 0x00007ffff6c8f76d libpthread.so.0`__GI_accept + 45, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff6c8f76d libpthread.so.0`__GI_accept + 45
    frame #&#8203;1: 0x0000000000437c2b TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_s5Int32VyXKfu_ + 123
    frame #&#8203;2: 0x0000000000441839 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_s5Int32VyXKfu_TA + 73
    frame #&#8203;3: 0x00000000004361a0 TestFoundation`_T014TestFoundation10_TCPSocketC7attempt33_AC276A005C0DEB782845E1C79EF92149LLs5Int32VSS_SS4fileSu4lineSbAGc5validAGyXKtKF + 144
    frame #&#8203;4: 0x0000000000437999 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_ + 409
    frame #&#8203;5: 0x0000000000437aef TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_TA + 95
    frame #&#8203;6: 0x0000000000437186 TestFoundation`_T0SpySC8sockaddrVGs5Error_pIxyzo_ACytsAD_pIxyrzo_TR + 22
    frame #&#8203;7: 0x0000000000437b9b TestFoundation`_T0SpySC8sockaddrVGs5Error_pIxyzo_ACytsAD_pIxyrzo_TRTA.13 + 91
    frame #&#8203;8: 0x00007ffff7aae937 libswiftCore.so`_T0SP17withMemoryReboundqd_0_qd__m2to_Si8capacityqd_0_SPyqd__GKctKr0_lF + 55
    frame #&#8203;9: 0x00007ffff7c7692f libswiftCore.so`_T0Sp17withMemoryReboundqd_0_qd__m2to_Si8capacityqd_0_Spyqd__GKctKr0_lF + 15
    frame #&#8203;10: 0x00000000004376c0 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKF + 512
    frame #&#8203;11: 0x000000000043ab07 TestFoundation`_T014TestFoundation11_HTTPServerC6listenyAA15ServerSemaphoreC6notify_tKF + 71
    frame #&#8203;12: 0x000000000043d63e TestFoundation`_T014TestFoundation0A16URLSessionServerC5startyAA0D9SemaphoreC7started_tKF + 94
    frame #&#8203;13: 0x00000000006c9f5d TestFoundation`_T014TestFoundation0A10URLSessionC9runServer33_F3FECA45EA2EBA0C2372DABFC6747FB7LLyAA0E9SemaphoreC4with_SdSg10startDelayAI04sendP0SiSg10bodyChunkstKF + 605
    frame #&#8203;14: 0x00000000006cca85 TestFoundation`_T014TestFoundation0A10URLSessionC27test_dataTaskWithURLRequestyyFyycfU_ + 133
    frame #&#8203;15: 0x00000000006d5c43 TestFoundation`_T014TestFoundation0A10URLSessionC27test_dataTaskWithURLRequestyyFyycfU_TA + 67
    frame #&#8203;16: 0x000000000043c1e9 TestFoundation`_T0Ix_IyB_TR + 41
    frame #&#8203;17: 0x00007ffff7ec8f37 libdispatch.so`_dispatch_call_block_and_release + 7
    frame #&#8203;18: 0x00007ffff7ed7455 libdispatch.so`_dispatch_root_queue_drain + 533
    frame #&#8203;19: 0x00007ffff7ef6f0f libdispatch.so`worker_main(unused=<unavailable>) + 207 at manager.c:506
    frame #&#8203;20: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;21: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

  thread #&#8203;6: tid = 8159, 0x00007ffff6c8f76d libpthread.so.0`__GI_accept + 45, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff6c8f76d libpthread.so.0`__GI_accept + 45
    frame #&#8203;1: 0x0000000000437c2b TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_s5Int32VyXKfu_ + 123
    frame #&#8203;2: 0x0000000000441839 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_s5Int32VyXKfu_TA + 73
    frame #&#8203;3: 0x00000000004361a0 TestFoundation`_T014TestFoundation10_TCPSocketC7attempt33_AC276A005C0DEB782845E1C79EF92149LLs5Int32VSS_SS4fileSu4lineSbAGc5validAGyXKtKF + 144
    frame #&#8203;4: 0x0000000000437999 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_ + 409
    frame #&#8203;5: 0x0000000000437aef TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKFySpySC8sockaddrVGKcfU_TA + 95
    frame #&#8203;6: 0x0000000000437186 TestFoundation`_T0SpySC8sockaddrVGs5Error_pIxyzo_ACytsAD_pIxyrzo_TR + 22
    frame #&#8203;7: 0x0000000000437b9b TestFoundation`_T0SpySC8sockaddrVGs5Error_pIxyzo_ACytsAD_pIxyrzo_TRTA.13 + 91
    frame #&#8203;8: 0x00007ffff7aae937 libswiftCore.so`_T0SP17withMemoryReboundqd_0_qd__m2to_Si8capacityqd_0_SPyqd__GKctKr0_lF + 55
    frame #&#8203;9: 0x00007ffff7c7692f libswiftCore.so`_T0Sp17withMemoryReboundqd_0_qd__m2to_Si8capacityqd_0_Spyqd__GKctKr0_lF + 15
    frame #&#8203;10: 0x00000000004376c0 TestFoundation`_T014TestFoundation10_TCPSocketC16acceptConnectionyAA15ServerSemaphoreC6notify_tKF + 512
    frame #&#8203;11: 0x000000000043ab07 TestFoundation`_T014TestFoundation11_HTTPServerC6listenyAA15ServerSemaphoreC6notify_tKF + 71
    frame #&#8203;12: 0x000000000043d63e TestFoundation`_T014TestFoundation0A16URLSessionServerC5startyAA0D9SemaphoreC7started_tKF + 94
    frame #&#8203;13: 0x00000000006c9f5d TestFoundation`_T014TestFoundation0A10URLSessionC9runServer33_F3FECA45EA2EBA0C2372DABFC6747FB7LLyAA0E9SemaphoreC4with_SdSg10startDelayAI04sendP0SiSg10bodyChunkstKF + 605
    frame #&#8203;14: 0x00000000006caa25 TestFoundation`_T014TestFoundation0A10URLSessionC20test_dataTaskWithURLyyFyycfU_ + 133
    frame #&#8203;15: 0x00000000006cab93 TestFoundation`_T014TestFoundation0A10URLSessionC20test_dataTaskWithURLyyFyycfU_TA + 67
    frame #&#8203;16: 0x000000000043c1e9 TestFoundation`_T0Ix_IyB_TR + 41
    frame #&#8203;17: 0x00007ffff7ec8f37 libdispatch.so`_dispatch_call_block_and_release + 7
    frame #&#8203;18: 0x00007ffff7ed7455 libdispatch.so`_dispatch_root_queue_drain + 533
    frame #&#8203;19: 0x00007ffff7ef6f0f libdispatch.so`worker_main(unused=<unavailable>) + 207 at manager.c:506
    frame #&#8203;20: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;21: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

  thread #&#8203;8: tid = 8275, 0x00007ffff5d08c21 libc.so.6`__GI_ppoll(fds=0x00007fffe5ffaa88, nfds=1, timeout=<unavailable>, sigmask=0x0000000000000000) + 145 at ppoll.c:50, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff5d08c21 libc.so.6`__GI_ppoll(fds=0x00007fffe5ffaa88, nfds=1, timeout=<unavailable>, sigmask=0x0000000000000000) + 145 at ppoll.c:50
    frame #&#8203;1: 0x00007ffff713aa31 libFoundation.so`__CFRunLoopServiceFileDescriptors + 225
    frame #&#8203;2: 0x00007ffff7136807 libFoundation.so`__CFRunLoopRun + 1095
    frame #&#8203;3: 0x00007ffff7136179 libFoundation.so`CFRunLoopRunSpecific + 489
    frame #&#8203;4: 0x00007ffff740427e libFoundation.so`_T010Foundation7RunLoopC3runyyF + 110
    frame #&#8203;5: 0x00007ffff745775d libFoundation.so`_T010Foundation7ProcessC5setup33_05FBE738056ADAC488E6D2B534411459LLyyFZyycfU_yycfU_ + 701
    frame #&#8203;6: 0x00007ffff7460877 libFoundation.so`_T010Foundation13NSThreadStart33_513815EE0AA0753AFF631398622CF939LLSvSgADF + 311
    frame #&#8203;7: 0x00007ffff7461859 libFoundation.so`_T010Foundation13NSThreadStart33_513815EE0AA0753AFF631398622CF939LLSvSgADFTo + 9
    frame #&#8203;8: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;9: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

  thread #&#8203;9: tid = 8276, 0x00007ffff5d0a9e3 libc.so.6`__GI_select + 51 at syscall-template.S:84, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff5d0a9e3 libc.so.6`__GI_select + 51 at syscall-template.S:84
    frame #&#8203;1: 0x00007ffff713ed0c libFoundation.so`__CFSocketManager + 652
    frame #&#8203;2: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;3: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

  thread #&#8203;10: tid = 8278, 0x00007ffff5d14e23 libc.so.6`__GI_epoll_wait + 51 at syscall-template.S:84, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff5d14e23 libc.so.6`__GI_epoll_wait + 51 at syscall-template.S:84
    frame #&#8203;1: 0x00007ffff7edf525 libdispatch.so`_dispatch_event_loop_drain + 53
    frame #&#8203;2: 0x00007ffff7edb2c8 libdispatch.so`_dispatch_mgr_invoke + 136
    frame #&#8203;3: 0x00007ffff7edb08b libdispatch.so`_dispatch_mgr_thread + 11
    frame #&#8203;4: 0x00007ffff7ed73b4 libdispatch.so`_dispatch_root_queue_drain + 372
    frame #&#8203;5: 0x00007ffff7ed71b8 libdispatch.so`_dispatch_worker_thread + 440
    frame #&#8203;6: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;7: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

  thread #&#8203;11: tid = 9095, 0x00007ffff6c8c709 libpthread.so.0`__pthread_cond_timedwait + 297, name = 'TestFoundation'
    frame #&#8203;0: 0x00007ffff6c8c709 libpthread.so.0`__pthread_cond_timedwait + 297
    frame #&#8203;1: 0x00007ffff7ef5fb4 libdispatch.so`overcommit_worker_main(unused=<unavailable>) + 340 at manager.c:326
    frame #&#8203;2: 0x00007ffff6c866ba libpthread.so.0`start_thread + 202
    frame #&#8203;3: 0x00007ffff5d1482d libc.so.6`__clone + 109 at clone.S:109

[pushkarnk]

thread #4 is of particular interest - it seems to be blocked on a Dispatch.sync call, the problem is that the stacks don't reveal any other task running on that queue

[eeckstein]

BTW, the same problem show up in other tests, like TestURLSession.test_taskTimeout:

https://ci.swift.org/job/oss-swift-package-linux-ubuntu-16_04/850/consoleFull#1369603219ee1a197b-acac-4b17-83cf-a53b95139a76

[swift-ci]

Comment by W S (JIRA)

FWIW, I believe I had timeout problems with (this?) URL test on AWS Linux since it was added. Unfortunately, I only ran the tests manually, and I believe the URLSession tests always failed, so I disabled them.
Maybe a change to dispatch is increasing occurrences of deadlock/whatever the underlying issue is?

[pushkarnk]

Two more failures in TestFoundation/TestNSURLSession:
https://bugs.swift.org/browse/SR-4655
https://bugs.swift.org/browse/SR-4677

[pushkarnk]

Came across the same failure with the `TestURLSession.test_verifyHttpAdditionalHeaders` test case

[pushkarnk]

The async barrier task is not executing at all, blocking all the subsequently dispatched task. Though we have a PR to work around this apparent issue, I'm going to assign this to Dispatch.

[swift-ci]

Comment by Mamatha Busi (JIRA)

Foundation PR for a workaround to this issue: swiftlang/swift-corelibs-foundation#982