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Date: Wed, 19 Nov 2014 13:40:45 +0100 From: Vitaly Kuznetsov <vkuznets@...hat.com> To: Dexuan Cui <decui@...rosoft.com> Cc: "gregkh\@linuxfoundation.org" <gregkh@...uxfoundation.org>, "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>, "driverdev-devel\@linuxdriverproject.org" <driverdev-devel@...uxdriverproject.org>, "olaf\@aepfle.de" <olaf@...fle.de>, "apw\@canonical.com" <apw@...onical.com>, "jasowang\@redhat.com" <jasowang@...hat.com>, Haiyang Zhang <haiyangz@...rosoft.com> Subject: Re: [PATCH] tools: hv: ignore ENOBUFS in the KVP daemon Dexuan Cui <decui@...rosoft.com> writes: >> -----Original Message----- >> From: Vitaly Kuznetsov >> Sent: Wednesday, November 19, 2014 18:50 PM >> To: Dexuan Cui >> Cc: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org; driverdev- >> devel@...uxdriverproject.org; olaf@...fle.de; apw@...onical.com; >> jasowang@...hat.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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