[SR-4039] Fix and re-enable dispatch_context_for_key on Linux

[swift-ci]

Previous ID	SR-4039
Radar	None
Original Reporter	das (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	libdispatch
Labels	Bug, Linux
Assignee	phabouzit (JIRA)
Priority	Medium

md5: bb27c0135c0da21d9cf4198a552922c2

Issue Description:

I had to temporarily move dispatch_context_for_key test into the unreliable tests with PR #220 because it started failing in the CI with https://ci.swift.org/job/swift-PR-Linux-smoke-test/5128/

This test doesn't fail on Darwin with libdispatch-806, we need to figure out why it does on Linux and fix and re-enable it

[swift-ci]

Comment by David Grove (JIRA)

I can reproduce a low-probability segfault in this test case by running it in a loop. The immediate symptom is that we are invoking the dx_push(dq, ..) macro on a dispatch queue_specific_queue. The do_push function for this type of queue is NULL, so we jump to 0x0 and crash.

A typical backtrace is:

(gdb) p *(dq)->do_vtable
$6 = {_os_obj_xref_dispose = 0x7f8dcf96c4e0 <_dispatch_xref_dispose>, _os_obj_dispose = 0x7f8dcf96c670 <_dispatch_dispose>, 
  _os_obj_vtable = {do_type = 65543, do_kind = 0x7f8dcf9b8746 "queue-context", do_invoke = 0x7f8dcf9801d0 <_dispatch_queue_invoke>, 
    do_push = 0x0, do_wakeup = 0x7f8dcf97c240 <_dispatch_queue_wakeup>, 
    do_dispose = 0x7f8dcf973930 <_dispatch_queue_specific_queue_dispose>, do_set_targetq = 0x0, do_suspend = 0x0, do_resume = 0x0, 
    do_finalize_activation = 0x0, do_debug = 0x7f8dcf975240 <dispatch_queue_debug>}}
(gdb) bt
#&#8203;0  0x0000000000000000 in ?? ()
#&#8203;1  0x00007f8dcf977ccf in _dispatch_barrier_async_detached_f (dq=0x7f8db4000990, ctxt=0x7f8db4000aa0, 
    func=0x7f8dcf9740b0 <_dispatch_queue_set_specific>) at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:3024
#&#8203;2  0x00007f8dcf9726d8 in _dispatch_barrier_trysync_or_async_f (dq=0x7f8db4000990, ctxt=0x7f8db4000aa0, 
    func=0x7f8dcf9740b0 <_dispatch_queue_set_specific>) at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:3682
#&#8203;3  0x00007f8dcf973e2e in dispatch_queue_set_specific (dq=0x7f8dbc000960, key=0x607158 <ctxts+8>, ctxt=0x405912, 
    destructor=0x401940 <destructor+64>) at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:2200
#&#8203;4  0x00000000004019e7 in __test_context_for_key_block_invoke_2 (.block_descriptor=0x607158 <ctxts+8>)
    at /home/dgrove/swift/swift-corelibs-libdispatch/tests/dispatch_context_for_key.c:79
#&#8203;5  0x00007f8dcf95d1f9 in _dispatch_call_block_and_release (block=0x7f8dbc000b60)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/init.c:924
#&#8203;6  0x00007f8dcf95d257 in _dispatch_client_callout (ctxt=0x7f8dbc000b60, f=0x7f8dcf95d1d0 <_dispatch_call_block_and_release>)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/init.c:951
#&#8203;7  0x00007f8dcf97ef25 in _dispatch_continuation_invoke_inline (dou=..., ov=0xffffffffffffffff, flags=65536)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/inline_internal.h:2301
#&#8203;8  _dispatch_continuation_pop_inline (dou=..., dic=0x7f8dcac32b18, flags=65536, dq=0x7f8dbc000960)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/inline_internal.h:2342
#&#8203;9  _dispatch_queue_drain (dq=0x7f8dbc000960, dic=0x7f8dcac32b18, flags=65536, owned_ptr=0x7f8dcac324c8, serial_drain=true)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:4261
#&#8203;10 _dispatch_queue_serial_drain (dq=0x7f8dbc000960, dic=0x7f8dcac32b18, flags=65536, owned=0x7f8dcac324c8)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:4317
#&#8203;11 0x00007f8dcf9814d7 in dispatch_queue_invoke2 (dq=0x7f8dbc000960, dic=0x7f8dcac32b18, flags=196608, owned=0x7f8dcac324c8)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:4660
#&#8203;12 0x00007f8dcf980b85 in _dispatch_queue_class_invoke (dou=..., dic=0x7f8dcac32b18, flags=196608, 
    invoke=0x7f8dcf981410 <dispatch_queue_invoke2>) at /home/dgrove/swift/swift-corelibs-libdispatch/src/inline_internal.h:1608
#&#8203;13 _dispatch_queue_invoke (dq=0x7f8dbc000960, dic=0x7f8dcac32b18, flags=196608)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:4672
#&#8203;14 0x00007f8dcf9780cd in _dispatch_continuation_pop_inline (dou=..., dic=0x7f8dcac32b18, flags=196608, dq=0x7f8dbc000a10)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/inline_internal.h:2340
#&#8203;15 _dispatch_continuation_pop (dou=..., dic=0x7f8dcac32b18, flags=196608, dq=0x7f8dbc000a10)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:4056
#&#8203;16 0x00007f8dcf9759a1 in _dispatch_async_redirect_invoke (dc=0x7f8db4000910, dic=0x7f8dcac32b18, flags=196608)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:3068
#&#8203;17 0x00007f8dcf987ed2 in _dispatch_continuation_pop_inline (dou=..., dic=0x7f8dcac32b18, flags=196608, 
    dq=0x7f8dcf9e7040 <_dispatch_root_queues+768>) at /home/dgrove/swift/swift-corelibs-libdispatch/src/inline_internal.h:2340
#&#8203;18 _dispatch_root_queue_drain (dq=0x7f8dcf9e7040 <_dispatch_root_queues+768>, pp=0)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:5382
#&#8203;19 0x00007f8dcf98718b in _dispatch_worker_thread4 (context=0x7f8dcf9e7040 <_dispatch_root_queues+768>)
    at /home/dgrove/swift/swift-corelibs-libdispatch/src/queue.c:5417
#&#8203;20 0x00007f8dcf9b799f in worker_main (unused=<optimized out>)
    at /home/dgrove/swift/swift-corelibs-libdispatch/libpwq/src/posix/manager.c:506
#&#8203;21 0x00007f8dcef606ba in start_thread (arg=0x7f8dcac33700) at pthread_create.c:333
#&#8203;22 0x00007f8dcec9682d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

[swift-ci]

Comment by Daniel A. Steffen (JIRA)

thanks, that sounds like a flaw in the vtable for these queues, Pierre ?

[swift-ci]

Comment by Pierre Habouzit (JIRA)

#223

[swift-ci]

Comment by Daniel A. Steffen (JIRA)

PR #223 merged