We are doing prototype so much change have gone into kernel , we are finding it difficult to upgrade to latest immediately However I ran through the code once again, indeed kernel handles it down_write(&mm->mmap_sem); in coredump_wait() makes sure the second coredump is stopped and returns negative for core_waiters I will debug further, thanks for confirming that kernel handles this scenario On Tue, Feb 17, 2015 at 9:57 PM, Sudharsan Vijayaraghavan <sudvijayr@xxxxxxxxx> wrote: > We are doing prototype so much change have gone into kernel , we are > finding it difficult to upgrade to latest immediately > However I ran through the code once again, indeed kernel handles it > down_write(&mm->mmap_sem); in coredump_wait() makes sure the second > coredump is stopped and returns negative for core_waiters > > I will debug further, thanks for confirming that kernel handles this scenario > > > On Tue, Feb 17, 2015 at 8:42 PM, Greg KH <greg@xxxxxxxxx> wrote: >> On Tue, Feb 17, 2015 at 07:11:55PM +0530, Sudharsan Vijayaraghavan wrote: >>> Hi All, >>> >>> We are running 3.8 kernel. >> >> That's pretty old and obsolete, why are you stuck with that version? >> >>> I have a unique scenario, where we hit on several issues in do_coredump. >>> We have a SMP system with thousands of cores, one pthread is tied to >>> one core. The main process containing these pthreads runs in the first >>> core. >>> >>> Here is the issue # 1 >>> When one of threads core dump, we enter into do_coredump(), now one >>> other thread in same process running in a different >>> core can as well core dump(before SIGKILL was delivered to it as a >>> consequence of first core dump) >>> This gives way to entering into do_coredump more than once. >>> Once we have two guys entering do_coredump() one can kill other with SIGKILL >>> the result is completely unpredictable. No guarantee we will have two >>> core files generated in the end >>> >>> Linux kernel does not seem to handle it at all. >>> Adding a spin lock within do_coredump() will solve the case of >>> multiple entries into do_coredump() >>> >>> I want to know whether Linux kernel really does not handle the above >>> case or am I missing something? >> >> Odd, we should handle this just fine, try emailing the developers >> responsible for this code and cc: the linux-kernel mailing list so they >> can work it out. >> >> thanks, >> >> greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
