Hello,
The ‘guix offload’ processes on berlin regularly hang while calling
‘channel-get-exit-status’:
--8<---------------cut here---------------start------------->8---
(gdb) bt
#0 0x00007f299fb330f1 in __GI___poll (fds=0x1dd58c0, nfds=1, timeout=-1) at
../sysdeps/unix/sysv/linux/poll.c:29
#1 0x00007f2994287577 in ssh_poll_ctx_dopoll () from
target:/gnu/store/wmpg67bn7i7pqc0p4xjp1npnqixk9znd-libssh-0.7.6/lib/libssh.so.4
#2 0x00007f29942884d9 in ssh_handle_packets () from
target:/gnu/store/wmpg67bn7i7pqc0p4xjp1npnqixk9znd-libssh-0.7.6/lib/libssh.so.4
#3 0x00007f29942885ad in ssh_handle_packets_termination () from
target:/gnu/store/wmpg67bn7i7pqc0p4xjp1npnqixk9znd-libssh-0.7.6/lib/libssh.so.4
#4 0x00007f2994275080 in ssh_channel_get_exit_status () from
target:/gnu/store/wmpg67bn7i7pqc0p4xjp1npnqixk9znd-libssh-0.7.6/lib/libssh.so.4
#5 0x00007f29946dd11a in guile_ssh_channel_get_exit_status () from
target:/gnu/store/i3nfl17wfx7sryq6w15r9wxl7ilmq4rb-guile-ssh-0.11.3/lib/libguile-ssh.so.11
#6 0x00007f29a1765965 in vm_regular_engine (thread=0x1dd58c0, vp=0x1d4df30,
registers=0xffffffff, resume=-1615646479) at vm-engine.c:786
#7 0x00007f29a1768fba in scm_call_n (proc=#<program 7f29a1be0030>,
argv=argv@entry=0x7ffc76b1ece8, nargs=nargs@entry=1) at vm.c:1257
#8 0x00007f29a16ecff7 in scm_primitive_eval (
exp=exp@entry=((@ (ice-9 control) %) (begin ((@@ (ice-9 command-line)
load/lang)
"/gnu/store/zz3b7j4iv6v143v7cqyr77k83zc5n3zw-guix-0.15.0-6.f9a8fce/bin/.guix-real")
(main (command-line)) (quit)))) at eval.c:662
#9 0x00007f29a16ed053 in scm_eval (
exp=((@ (ice-9 control) %) (begin ((@@ (ice-9 command-line) load/lang)
"/gnu/store/zz3b7j4iv6v143v7cqyr77k83zc5n3zw-guix-0.15.0-6.f9a8fce/bin/.guix-real")
(main (command-line)) (quit))),
module_or_state=module_or_state@entry="#<struct module>" = {...}) at eval.c:696
#10 0x00007f29a1738220 in scm_shell (argc=11, argv=0x1dd5280) at script.c:454
(gdb) frame 0
#0 0x00007f299fb330f1 in __GI___poll (fds=0x1dd58c0, nfds=1, timeout=-1) at
../sysdeps/unix/sysv/linux/poll.c:29
29 in ../sysdeps/unix/sysv/linux/poll.c
(gdb) p *fds
$1 = {fd = 14, events = 1, revents = 0}
(gdb) shell ls -l /proc/12605/fd
total 0
lr-x------ 1 root root 64 Nov 2 11:20 0 -> 'pipe:[44413497]'
l-wx------ 1 root root 64 Nov 2 11:33 1 -> 'pipe:[44413496]'
lr-x------ 1 root root 64 Nov 2 11:33 10 -> 'pipe:[44459532]'
l-wx------ 1 root root 64 Nov 2 11:33 11 -> 'pipe:[44459532]'
lr-x------ 1 root root 64 Nov 2 11:33 12 -> 'pipe:[44429590]'
l-wx------ 1 root root 64 Nov 2 11:33 13 -> 'pipe:[44429590]'
lrwx------ 1 root root 64 Nov 2 11:33 14 -> 'socket:[44444783]'
lrwx------ 1 root root 64 Nov 2 11:33 15 -> 'socket:[44444784]'
l-wx------ 1 root root 64 Nov 2 11:33 16 -> /var/guix/offload/141.80.167.140/0
l-wx------ 1 root root 64 Nov 2 11:33 2 -> 'pipe:[44413496]'
lr-x------ 1 root root 64 Nov 2 11:33 3 -> 'pipe:[44459528]'
lr-x------ 1 root root 64 Nov 2 11:33 33 -> /dev/urandom
l-wx------ 1 root root 64 Nov 2 11:33 4 -> 'pipe:[44413498]'
l-wx------ 1 root root 64 Nov 2 11:33 5 -> 'pipe:[44459528]'
lr-x------ 1 root root 64 Nov 2 11:33 6 -> 'pipe:[44459531]'
l-wx------ 1 root root 64 Nov 2 11:33 7 -> 'pipe:[44459531]'
lr-x------ 1 root root 64 Nov 2 11:33 8 -> 'pipe:[44453928]'
l-wx------ 1 root root 64 Nov 2 11:33 9 -> 'pipe:[44453928]'
--8<---------------cut here---------------end--------------->8---
I believe this is because in (guix ssh) we don’t ensure the remote
process is dead by the time we call ‘channel-get-exit-status’, as in
this example:
--8<---------------cut here---------------start------------->8---
scheme@(guix ssh)> (define s (open-ssh-session "localhost" #:user "ludo" #:port
22))
scheme@(guix ssh)> (define c (open-remote-pipe* s OPEN_BOTH "sleep 1000"))
scheme@(guix ssh)> (channel-send-eof c)
$4 = #<undefined>
scheme@(guix ssh)> (channel-get-exit-status c)
;; hangs
--8<---------------cut here---------------end--------------->8---
Problem is that calling ‘channel-get-exit-status’ on a closed port
doesn’t work, so forcing a port close isn’t really an option:
--8<---------------cut here---------------start------------->8---
scheme@(guix ssh)> (define c (open-remote-pipe* s OPEN_BOTH "sleep 100"))
scheme@(guix ssh)> (close-port c)
$4 = #t
scheme@(guix ssh)> (channel-get-exit-status c)
ERROR: In procedure channel-get-exit-status:
In procedure channel-get-exit-status: Wrong type argument in position 1
(expecting open channel): #<unknown channel (freed) 221d5c0>
--8<---------------cut here---------------end--------------->8---
To be continued…
Ludo’.
