Re: nosh: service-dt-scanner gets repeatedly killed by SIGABRT

From: Guillermo <gdiazhartusch_at_gmail.com>
Date: Thu, 9 Jul 2015 23:02:48 -0300

2015-07-08 5:30 GMT-03:00 Jonathan de Boyne Pollard:
>
> If there's no error output, crank up strace and see what the last few system
> calls are. It's probably worthwhile doing that anyway, in fact.

Here are the last system calls shown by an strace of
service-dt-scanner before the SIGABRT, with some relevant previous
lines. The specific test was using ls on the service's bundle
directory, which was a direct subdirectory of the scan directory, and
had daemontools-compatible layout.

At one point, this happens:

epoll_create(1) = 4
openat(AT_FDCWD, "scandir",
O_RDONLY|O_NOCTTY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 6
gettid() = 1328
fstat64(6, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0

Then there is a readlink() call on "/proc/1328/fd/6" ("scandir"
happened to be a symbolic link) and then:

inotify_init() = 7
inotify_add_watch(7, "/path-to/test/scandir", IN_MODIFY|IN_ATTRIB|IN_CLOSE) = 1
epoll_ctl(4, EPOLL_CTL_ADD, 7, {EPOLLIN, {u32=159460944, u64=159460944}}) = 0

"/path-to/test/scandir" represents here what was the complete path to
the scan directory.

And now the complete final lines:

fstatat64(11, "down", 0xbfe6af30, 0) = -1 ENOENT (No such file or directory)
rt_sigaction(SIGALRM, {0x806e971, [], 0}, {SIG_DFL, [], 0}, 8) = 0
alarm(5) = 0
openat(12, "ok", O_WRONLY|O_NOCTTY|O_CLOEXEC) = 13
close(13) = 0
alarm(0) = 5
rt_sigaction(SIGALRM, {SIG_DFL, [], 0}, NULL, 8) = 0
openat(12, "control", O_WRONLY|O_NOCTTY|O_NONBLOCK|O_CLOEXEC) = 13
write(13, "u", 1) = 1
close(13) = 0
close(12) = 0
close(11) = 0
close(10) = 0
getdents(9, /* 0 entries */, 32768) = 0
close(9) = 0

(File descriptors were 9 = the scan directory, after a dup(6), 10 =
bundle directory of the service, 11 was the result of a dup(10), 12 =
supervise/ subdirectory of the service's bundle directory)

epoll_wait(4, {{EPOLLIN, {u32=159460944, u64=159460944}}}, 1, -1) = 1
gettid() = 1328
read(7, "\1\0\0\0\20\0\0_at_\0\0\0\0\0\0\0\0", 16) = 16
write(2, "service-dt-scanner: DEBUG: event"..., 59) = 59

(That was an ls command on the scan directory, that produced this
output: "service-dt-scanner: DEBUG: event filter 0 ident 6 fflags 6")

epoll_wait(4, {{EPOLLIN, {u32=159460944, u64=159460944}}}, 1, -1) = 1
gettid() = 1328
read(7, 0xbfe6b0cc, 16) = -1 EINVAL (Invalid argument)
rt_sigprocmask(SIG_UNBLOCK, [ABRT], NULL, 8) = 0
tgkill(1328, 1328, SIGABRT) = 0
--- SIGABRT {si_signo=SIGABRT, si_code=SI_TKILL, si_pid=1328, si_uid=1000} ---
+++ killed by SIGABRT +++

I did the strace a couple of different times, and all outputs ended
like this, a read() call on the file descriptor returned by the
inotify_init() that produces an EINVAL error, followed
rt_sigprocmask() with a SIG_UNBLOCK argument, and the tgkill() that
sends the SIGABRT.

Thanks,
G.
Received on Fri Jul 10 2015 - 02:02:48 UTC