[Bug 211947] bconsole won't die sitting on do_rw_wrlock
bugzilla-noreply at freebsd.org
bugzilla-noreply at freebsd.org
Sat Aug 20 20:52:57 UTC 2016
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=211947
longwitz at incore.de changed:
What |Removed |Added
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CC| |longwitz at incore.de
--- Comment #1 from longwitz at incore.de ---
I need help with this problem and give some more infos:
bconsole creates two threads: watchdog and checker_deadlock. When trying to
quit bconsole the main thread sends first a special ping to the watchdog thread
and this thread always stops cleanly without any problems. Second the main
thread tries to stop the sleeping thread checker_deadlock with
pthread_cancel(). Both the main thread and the checker_deadlock thread do some
housekeeping in exit routines. I give ktraces of good and bad case starting
with pthread_cancel:
good (quit exits normally):
54503 100490 bconsole CALL thr_kill(0x18b71,SIG 32)
54503 100490 bconsole RET thr_kill 0
54503 101233 bconsole RET nanosleep -1 errno 4 Interrupted system call
54503 101233 bconsole PSIG SIG 32 caught handler=0x80205b080 mask=0x0
code=SI_LWP
54503 100490 bconsole CALL _umtx_op(0x802270880,UMTX_OP_RW_WRLOCK,0,0,0)
54503 101233 bconsole CALL thr_wake(0x18b71)
54503 100490 bconsole RET _umtx_op 0
54503 101233 bconsole RET thr_wake 0
54503 101233 bconsole CALL thr_wake(0x18b71)
54503 101233 bconsole RET thr_wake 0
54503 101233 bconsole CALL sigreturn(0x7fffdfffda60)
54503 101233 bconsole RET sigreturn JUSTRETURN
54503 100490 bconsole CALL _umtx_op(0x802270880,UMTX_OP_RW_WRLOCK,0,0,0)
54503 100490 bconsole RET _umtx_op 0
54503 101233 bconsole CALL _umtx_op(0x802270880,UMTX_OP_RW_RDLOCK,0,0,0)
54503 101233 bconsole RET _umtx_op 0
54503 100490 bconsole CALL _umtx_op(0x802270880,UMTX_OP_RW_WRLOCK,0,0,0)
54503 100490 bconsole RET _umtx_op 0
54503 101233 bconsole CALL _umtx_op(0x802270880,UMTX_OP_RW_RDLOCK,0,0,0)
54503 101233 bconsole RET _umtx_op 0
54503 100490 bconsole CALL _umtx_op(0x802270880,UMTX_OP_RW_WRLOCK,0,0,0)
54503 101233 bconsole CALL _umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
54503 101233 bconsole RET _umtx_op 0
54503 100490 bconsole RET _umtx_op 0
54503 101233 bconsole CALL _umtx_op(0x802270880,UMTX_OP_RW_RDLOCK,0,0,0)
54503 101233 bconsole RET _umtx_op 0
54503 101233 bconsole CALL munmap(0x800663000,0x1000)
54503 101233 bconsole RET munmap 0
54503 101233 bconsole CALL madvise(0x803806000,0x8000,MADV_FREE)
54503 101233 bconsole RET madvise 0
54503 100490 bconsole CALL exit(0)
54503 101233 bconsole CALL thr_exit(0x803406800)
bad (hang on quit):
62196 100096 bconsole 0.655701 CALL thr_kill(0x186f8,SIG 32)
62196 100096 bconsole 0.655717 RET thr_kill 0
62196 100088 bconsole 0.655726 RET nanosleep -1 errno 4 Interrupted system
call
62196 100088 bconsole 0.655742 PSIG SIG 32 caught handler=0x80205b080
mask=0x0 code=SI_LWP
62196 100096 bconsole 0.655766 CALL
_umtx_op(0x802270880,UMTX_OP_RW_WRLOCK,0,0,0)
62196 100088 bconsole 0.655770 CALL thr_wake(0x186f8)
62196 100096 bconsole 0.655774 RET _umtx_op 0
62196 100088 bconsole 0.655781 RET thr_wake 0
62196 100088 bconsole 0.655791 CALL thr_wake(0x186f8)
62196 100088 bconsole 0.655795 RET thr_wake 0
62196 100088 bconsole 0.655800 CALL sigreturn(0x7fffdfffda60)
62196 100088 bconsole 0.655807 RET sigreturn JUSTRETURN
62196 100096 bconsole 0.655830 CALL
_umtx_op(0x802270880,UMTX_OP_RW_WRLOCK,0,0,0)
62196 100096 bconsole 0.655837 RET _umtx_op 0
62196 100088 bconsole 0.655838 CALL
_umtx_op(0x802270880,UMTX_OP_RW_RDLOCK,0,0,0)
62196 100088 bconsole 0.655848 RET _umtx_op 0
62196 100096 bconsole 0.655848 CALL
_umtx_op(0x802270880,UMTX_OP_RW_WRLOCK,0,0,0)
62196 100088 bconsole 0.655862 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.655875 RET _umtx_op 0
62196 100088 bconsole 0.655885 CALL
_umtx_op(0x802270880,UMTX_OP_RW_RDLOCK,0,0,0)
62196 100096 bconsole 0.655885 RET _umtx_op 0
62196 100088 bconsole 0.655897 RET _umtx_op -1 errno 4 Interrupted system
call
62196 100096 bconsole 0.655901 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.655903 CALL
_umtx_op(0x802270880,UMTX_OP_RW_RDLOCK,0,0,0)
62196 100096 bconsole 0.655912 RET _umtx_op 0
62196 100088 bconsole 0.655915 RET _umtx_op 0
62196 100096 bconsole 0.655930 CALL
_umtx_op(0x802270880,UMTX_OP_RW_WRLOCK,0,0,0)
62196 100088 bconsole 0.655930 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.655942 RET _umtx_op 0
62196 100088 bconsole 0.655952 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.655956 RET _umtx_op 0
62196 100088 bconsole 0.655966 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.655971 RET _umtx_op 0
62196 100088 bconsole 0.655978 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.655982 RET _umtx_op 0
62196 100088 bconsole 0.655989 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.655993 RET _umtx_op 0
62196 100088 bconsole 0.655999 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.656005 RET _umtx_op 0
62196 100088 bconsole 0.656010 CALL80,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.656014 RET _umtx_op 0
62196 100088 bconsole 0.656022 CALL
_umtx_op(0x802270880,UMTX_OP_RW_UNLOCK,0,0,0)
62196 100088 bconsole 0.656026 RET _umtx_op 0
62196 100088 bconsole 0.656032 CALL munmap(0x800663000,0x1000)
62196 100088 bconsole 0.656042 RET munmap 0
62196 100088 bconsole 0.656089 CALL madvise(0x803806000,0x8000,MADV_FREE)
62196 100088 bconsole 0.656099 RET madvise 0
62196 100088 bconsole 0.656105 CALL thr_exit(0x803406800)
and the main thread does not die, he sits on WCHAN uwrlck. Especially I like to
know, why the kernel sends a second signal to the checker_deadlock thread.
I can avoid the libthr/kernel problem by sleeping some ms in the main thread
after pthread_cancel(), the resulting ktrace looks like rather clean, because
no _umtx_op calls to the kernel are necessary:
81803 100271 bconsole 8.425361 CALL thr_kill(0x18a20,SIG 32)
81803 100271 bconsole 8.425374 RET thr_kill 0
81803 100271 bconsole 8.425380 CALL nanosleep(0x7fffffffe2f0,0)
81803 100896 bconsole 8.425382 RET nanosleep -1 errno 4 Interrupted system
call
81803 100896 bconsole 8.425400 PSIG SIG 32 caught handler=0x80205b080
mask=0x0 code=SI_LWP
81803 100896 bconsole 8.425426 CALL thr_wake(0x18a20)
81803 100896 bconsole 8.425433 RET thr_wake 0
81803 100896 bconsole 8.425438 CALL thr_wake(0x18a20)
81803 100896 bconsole 8.425442 RET thr_wake 0
81803 100896 bconsole 8.425446 CALL sigreturn(0x7fffdfffda60)
81803 100896 bconsole 8.425452 RET sigreturn JUSTRETURN
81803 100896 bconsole 8.425519 CALL munmap(0x800663000,0x1000)
81803 100896 bconsole 8.425529 RET munmap 0
81803 100896 bconsole 8.425575 CALL madvise(0x80380e000,0x22000,MADV_FREE)
81803 100896 bconsole 8.425585 RET madvise 0
81803 100896 bconsole 8.425595 CALL madvise(0x803806000,0x8000,MADV_FREE)
81803 100896 bconsole 8.425603 RET madvise 0
81803 100896 bconsole 8.425609 CALL thr_exit(0x803406800)
81803 100271 bconsole 8.427522 RET nanosleep 0
81803 100271 bconsole 8.427717 CALL exit(0)
In my opinion this problem must be solved in libthr/kernel and not in userland.
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