> Von: Florian Kelbert [mailto:florian_kelb...@gmx.de] > > On 20.05.2014 16:36, Fiedler Roman wrote: > > Hello List, > > > > I'm using strace for quite a while, but today I got a quite unexpected > > result. Since this was so confusing, I would be glad about feedback, if the > > cause for that could be a) human error in operation of strace, b) > > misconception of the principles of syscall tracing, c) some strange > > interaction between 32bit kernel/binary on single-core CPU: > > > > The output: > > > > # strace -s256 -f /usr/sbin/zabbix_server -c /etc/zabbix/zabbix_server.conf > > .... > > setgroups32(1, [112]) = 0 > > setuid32(109) = 0 > > setresgid32(-1, 112, -1) = 0 > > setresuid32(-1, 109, -1) = 0 > > clone(child_stack=0, > flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, > > child_tidptr=0xb6340768) = 30111 > > exit_group(0) = ? > > +++ exited with 0 +++ > > > > > > What was unexpected: strace failed to attach to the child. What is special > > about the traced process: due to an error, the child process performs just > > one open-syscall and exit after clone, the parent process performs an exit > > immediately after clone. Due to single-core CPU, it seems more likely, that > > the parent continues running after the fork before the child process gets > > any chance to do so. > > > > Question: Is my strace invocation syntax correct and should it capture the > > child system calls also? To my understanding, a tracee should be stopped as > > soon as strace is attached, also all children are stopped after clone. So > > there should be no way to miss any child? > > > > Kind regards, > > Roman > > > > > > PS: I'm using strace version: > > ii strace 4.8-1ubuntu5 i386 > > A system call tracer > > > > It seems that the problem you describe has already been filed, discussed > and fixed: > https://www.mail-archive.com/strace- > de...@lists.sourceforge.net/msg03273.html
Thanks for the pointer. The commit fixing that seems to be [1], but the packages from Ubuntu seem to be too old to include that change (although LTS was released 2014-04 and fix is from 2013-07-08). I've created a bug-report at launchpad about that, see [2]. Kind regards, Roman [1] http://sourceforge.net/p/strace/code/ci/d2e1f42d8a28486484f00739e561a58be480 8b03/ [2] https://bugs.launchpad.net/ubuntu/+source/strace/+bug/1321383
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