Vegard (and Quentin): Ping! On 05/15/2015 02:05 PM, Michael Kerrisk (man-pages) wrote: > 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
