Eric Wong <normalperson@xxxxxxxx> wrote: > This patch seems to fix my issue with ppoll() being stuck on my > SMP machine: http://article.gmane.org/gmane.linux.file-systems/70414 OK, it doesn't fix my issue, but it seems to make it harder-to-hit... > The change to sock_poll_wait() in > commit 626cf236608505d376e4799adb4f7eb00a8594af > (poll: add poll_requested_events() and poll_does_not_wait() functions) > seems to have allowed additional cases where the SMP memory barrier > is not issued before checking for readiness. > > In my case, this affects the select()-family of functions > which register descriptors once and set _qproc to NULL before > checking events again (after poll_schedule_timeout() returns). > The set_mb() barrier in poll_schedule_timeout() appears to be > insufficient on my SMP x86-64 machine (as it's only an xchg()). > > This may also be related to the epoll issue described by > Andreas Voellmy in http://thread.gmane.org/gmane.linux.kernel/1408782/ However, I believe my patch will still fix Andreas' issue with epoll due to how ep_modify() uses a NULL qproc when calling ->poll(). (I've never been able to reproduce Andreas' issue on my 4-core system, but he's been hitting it since 3.4 (at least)) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
