From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754376AbaKSMlB (ORCPT ); Wed, 19 Nov 2014 07:41:01 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47622 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754175AbaKSMk7 (ORCPT ); Wed, 19 Nov 2014 07:40:59 -0500 From: Vitaly Kuznetsov To: Dexuan Cui Cc: "gregkh\@linuxfoundation.org" , "linux-kernel\@vger.kernel.org" , "driverdev-devel\@linuxdriverproject.org" , "olaf\@aepfle.de" , "apw\@canonical.com" , "jasowang\@redhat.com" , Haiyang Zhang Subject: Re: [PATCH] tools: hv: ignore ENOBUFS in the KVP daemon References: <1416394245-31717-1-git-send-email-decui@microsoft.com> <87lhn7forv.fsf@vitty.brq.redhat.com> Date: Wed, 19 Nov 2014 13:40:45 +0100 In-Reply-To: (Dexuan Cui's message of "Wed, 19 Nov 2014 12:15:21 +0000") Message-ID: <87egszfjn6.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dexuan Cui writes: >> -----Original Message----- >> From: Vitaly Kuznetsov >> Sent: Wednesday, November 19, 2014 18:50 PM >> To: Dexuan Cui >> Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; driverdev- >> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com; >> jasowang@redhat.com; Haiyang Zhang >> Subject: Re: [PATCH] tools: hv: ignore ENOBUFS in the KVP daemon >> >> Dexuan Cui writes: >> >> > Under high memory pressure and very high KVP R/W test pressure, the netlink >> > recvfrom() may transiently return ENOBUFS to the daemon -- we found this >> > during a 2-week stress test. >> > >> > We'd better not terminate the daemon on this failure, because a typical KVP >> > user can re-try the R/W and hopefully it will succeed next time. >> > >> > diff --git a/tools/hv/hv_kvp_daemon.c b/tools/hv/hv_kvp_daemon.c >> > index 22b0764..9f4b303 100644 >> > --- a/tools/hv/hv_kvp_daemon.c >> > +++ b/tools/hv/hv_kvp_daemon.c >> > @@ -1559,8 +1559,15 @@ int main(int argc, char *argv[]) >> > addr_p, &addr_l); >> > >> > if (len < 0) { >> > + int saved_errno = errno; >> > syslog(LOG_ERR, "recvfrom failed; pid:%u error:%d %s", >> > addr.nl_pid, errno, strerror(errno)); >> > + >> > + if (saved_errno == ENOBUFS) { >> >> is it possible to meet EAGAIN (or EWOULDBLOCK) here as well? I'd suggest >> we ignore these as well in such case. Ignoring ENOMEM here is doubtful, >> I think. But possible. >> >> Vitaly > > I don't think EAGAIN is possible because "man recvfrom" says > "If no messages are available at the socket, the receive calls wait for a > message to arrive, unless the socket is nonblocking (see fcntl(2)), in which > case the value -1 is returned and the external variable errno is set to > EAGAIN or EWOULDBLOCK". > > The same man page mention ENOMEM for recvmsg(), but not recvfrom(). Ah, sorry, I though your patch patches the other place: call to netlink_send() which does sendmsg() (and my EAGAIN/EWOULDBLOCK/ENOMEM comment was about it). It could also make sense to patch them both as I think it is possible to hit these as well. > > -- Dexuan -- Vitaly