On 05/14/2015 03:44 PM, Michael Kerrisk (man-pages) wrote: > Hi Denys, > > Do you have any thoughts on the below? Yes, the poster is right: this part needs fixing, the behavior is the same on any kind of process termination. > On 05/12/2015 04:31 PM, Vegard Nossum wrote: >> We hit another edge case in the ptrace() interface and after several >> hours of chasing it down, we found that it was already described in the >> "BUGS" section: >> >> "If a thread group leader is traced and exits by calling _exit(2), a I think a possible fix is just to replace "exits by calling _exit(2)" part of the above text with "terminates". >> PTRACE_EVENT_EXIT stop will happen for it (if requested), but the >> subsequent WIFEXITED notification will not be delivered until all other >> threads exit. As explained above, if one of other threads calls >> execve(2), the death of the thread group leader will never be reported. >> If the execed thread is not traced by this tracer, the tracer will never >> know that execve(2) happened. One possible workaround is to >> PTRACE_DETACH the thread group leader instead of restarting it in this >> case. Last confirmed on 2.6.38.6." >> >> I wanted to write that we've also noticed the same thing not only for >> _exit() but also for terminating signals, however we also came across >> this bit in the manual source: >> >> .\" Note from Denys Vlasenko: >> .\" Here "exits" means any kind of death - _exit, exit_group, >> .\" signal death. Signal death and exit_group cases are trivial, >> .\" though: since signal death and exit_group kill all other threads >> .\" too, "until all other threads exit" thing happens rather soon >> .\" in these cases. Therefore, only _exit presents observably >> .\" puzzling behavior to ptrace users: thread leader _exit's, >> .\" but WIFEXITED isn't reported! We are trying to explain here >> .\" why it is so. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
