Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755086AbaKSNFb (ORCPT ); Wed, 19 Nov 2014 08:05:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60347 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754897AbaKSNF2 (ORCPT ); Wed, 19 Nov 2014 08:05:28 -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> <87egszfjn6.fsf@vitty.brq.redhat.com> Date: Wed, 19 Nov 2014 14:05:12 +0100 In-Reply-To: (Dexuan Cui's message of "Wed, 19 Nov 2014 12:57:24 +0000") Message-ID: <87a93nfiif.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 [mailto:vkuznets@redhat.com] >> Sent: Wednesday, November 19, 2014 20:41 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: >> >> >> -----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 > > OK, I can add this new check: > (I'll send out the v2 tomorrow in case people have new comments) > Thanks! > --- a/tools/hv/hv_kvp_daemon.c > +++ b/tools/hv/hv_kvp_daemon.c > @@ -1770,8 +1770,15 @@ kvp_done: > > len = netlink_send(fd, incoming_cn_msg); > if (len < 0) { > + int saved_errno = errno; > syslog(LOG_ERR, "net_link send failed; error: %d %s", errno, > strerror(errno)); > + > + if (saved_errno == ENOMEM || saved_errno == EAGAIN) { Sorry for being pushy, but it seems ENOBUFS is also possible here (at least man sendmsg mentions it). > + syslog(LOG_ERR, "send error: ignored"); > + continue; > + } > + > exit(EXIT_FAILURE); > } > } > > Thanks, > -- Dexuan -- Vitaly -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/