Hi Vegard, On 15 May 2015 at 12:12, Vegard Nossum <vegard.nossum@xxxxxxxxxx> wrote: > On 05/14/2015 06:39 PM, Denys Vlasenko wrote: >> >> On 05/14/2015 06:28 PM, Quentin Casasnovas wrote: >>> >>> On Thu, May 14, 2015 at 03:52:36PM +0200, Denys Vlasenko wrote: >>>> >>>> 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". >>>> >>> >>> Should we also add a little paragraph detailing that waitpid() would hang >>> indefinitely if one thread terminates while the others are in >>> ptrace-stop? >> >> >> It implies this by saying "but the subsequent WIFEXITED notification >> will not be delivered until all other threads exit". >> >> If another thread is in ptrace-stop, it did not exit yet. Therefore, >> WIFEXITED notification to the thread group leader will not be delivered. >> Therefore, waitpid() on it would hang. > > > While I agree that the information in the current man page is strictly > speaking sufficient, I personally still think it would be an improvement > to mention it explicitly (i.e. my proposed change #2 in the original > e-mail). Just because I think it's a sort of non-obvious pitfall; out of > hand, you don't expect a call to waitpid() on a process that has exited > to hang. That's just my opinion, though. That sounds okay to me. Would you and/or Quentin be willing to put together a patch to the man page? Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- 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
