GNU bug report logs - #42353
mcron occasionally gets stuck in pre-fork

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Package: guix; Severity: important; Reported by: Ludovic Courtès <ludo@HIDDEN>; dated Tue, 14 Jul 2020 14:17:02 UTC; Maintainer for guix is bug-guix@HIDDEN.
Severity set to 'important' from 'normal' Request was from Ludovic Courtès <ludo@HIDDEN> to control <at> debbugs.gnu.org. Full text available.

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From: =?utf-8?Q?Ludovic_Court=C3=A8s?= <ludo@HIDDEN>
To: <bug-guix@HIDDEN>
Subject: mcron occasionally gets stuck in pre-fork
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Hi,

mcron running on top of Guile 3.0.2 occasionally gets stuck right before
fork while shutting down the finalization thread:

--8<---------------cut here---------------start------------->8---
ludo@berlin ~$ ps aux|grep 25457
root      25457  0.0  0.0 149576  9412 ?        Ssl  Jul10   0:00 /gnu/stor=
e/fp5ybkawldy28kzkzp60s23hkqbdx4x2-mcron-1.1.4/bin/mcron /gnu/store/l74fbl7=
si93si6x47sfwsnc9ag386570-mcron-job /gnu/store/r11ffr5rfkqyw1drqrqabwx210lk=
1jfn-mcron-job /gnu/store/3a88kc90lv6nqy9k1bwkxpi9gps1vfdb-mcron-job /gnu/s=
tore/8386w15b7mj1pmjbp5n9jk6p2v9b0m2q-mcron-job /gnu/store/v0jwrr7ggwvr6y4x=
vqwiqksbrgkmm21c-mcron-job /gnu/store/wzv96j9c1h86kfzl5ai64j1xwvkin1wz-mcro=
n-job /gnu/store/kz93w89b7sj6gz32aq6flsy0pa3ag6ny-mcron-job /gnu/store/4jv4=
ap1d161dvix472j47lipvqafqrmn-mcron-job /gnu/store/r7vs7vkid8w1xz0nzkcwc6ylm=
z8yryc5-mcron-job /gnu/store/yy51bjcx0zndsn9db56sb2d1bn7c9j1i-mcron-job /gn=
u/store/56vfqmzfidcf1axh07zak2gfbgrc8jdm-mcron-job
ludo     130462  0.0  0.0   6376  2476 pts/11   S+   16:10   0:00 grep --co=
lor 25457
ludo@berlin ~$ sudo gdb -ix ~/.gdbinit -p 25457
GNU gdb (GDB) 8.3.1

[=E2=80=A6]

(gdb) bt
#0  0x00007f38221a1517 in __pthread_clockjoin_ex ()
   from /gnu/store/fa6wj5bxkj5ll1d7292a70knmyl7a0cr-glibc-2.31/lib/libpthre=
ad.so.0
#1  0x00007f38222960d8 in stop_finalization_thread () at finalizers.c:276
#2  0x00007f38222962f9 in scm_i_finalizer_pre_fork () at finalizers.c:301
#3  0x00007f382231e1d6 in scm_fork () at posix.c:1230
#4  0x00007f38193b2def in ?? ()
#5  0x00007f3821bc9d80 in ?? ()
#6  0x00007f38223795c0 in ?? ()
   from /gnu/store/18hp7flyb3yid3yp49i6qcdq0sbi5l1n-guile-3.0.2/lib/libguil=
e-3.0.so.1
#7  0x00007f3821bc9d80 in ?? ()
#8  0x00007f38222b2f0b in scm_jit_enter_mcode (thread=3D0x7f3821bc9d80,
    mcode=3D0x7f38193accd2 "I\211\314I)\304I\203\374\060\017\214s\003")
    at jit.c:5777
#9  0x00007f382230e350 in vm_regular_engine (thread=3D0x7f38193b2dd0)
    at vm-engine.c:546
#10 0x00007f382230f175 in scm_call_n (proc=3D<optimized out>,
    argv=3Dargv@entry=3D0x7ffd8ff6ad58, nargs=3Dnargs@entry=3D1) at vm.c:16=
08
#11 0x00007f382228c078 in scm_call_1 (proc=3D<optimized out>,
    arg1=3D<optimized out>) at eval.c:496
#12 0x000000000040130c in inner_main ()
#13 0x00007f38222a4c0d in invoke_main_func (body_data=3D0x7ffd8ff6b240)
    at init.c:308

[=E2=80=A6]

(gdb) thread apply all bt
Thread 17 (Thread 0x7f3819c7d700 (LWP 15795)):
#0  0x00007f38221aa0a4 in read () from /gnu/store/fa6wj5bxkj5ll1d7292a70knm=
yl7a0cr-glibc-2.31/lib/libpthread.so.0
#1  0x00007f3822296067 in read_finalization_pipe_data (data=3D0x7f3819c7ca3=
0) at finalizers.c:205
#2  0x00007f38221e8d94 in GC_do_blocking_inner () from /gnu/store/zg126cjic=
rpm2p6zc08ra5vh4ddag7ww-libgc-8.0.4/lib/libgc.so.1
#3  0x00007f38221e59c2 in GC_with_callee_saves_pushed () from /gnu/store/zg=
126cjicrpm2p6zc08ra5vh4ddag7ww-libgc-8.0.4/lib/libgc.so.1
#4  0x00007f38221e5a6c in GC_do_blocking () from /gnu/store/zg126cjicrpm2p6=
zc08ra5vh4ddag7ww-libgc-8.0.4/lib/libgc.so.1
#5  0x00007f38223036b5 in scm_without_guile (func=3D0x7f3822296050 <read_fi=
nalization_pipe_data>, data=3D0x7f3819c7ca30) at threads.c:706
#6  0x00007f382229641b in finalization_thread_proc (unused=3D<optimized out=
>) at finalizers.c:218
--8<---------------cut here---------------end--------------->8---

This reminds me of <https://issues.guix.info/31925> and more recently
this issue Mathieu reported: <https://issues.guix.gnu.org/41948>.

It could be that Guile still has troubles shutting down the finalization
thread.

Ludo=E2=80=99.




Acknowledgement sent to Ludovic Courtès <ludo@HIDDEN>:
New bug report received and forwarded. Copy sent to othacehe@HIDDEN, bug-guix@HIDDEN. Full text available.
Report forwarded to othacehe@HIDDEN, bug-guix@HIDDEN:
bug#42353; Package guix. Full text available.
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