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
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