> -----Original Message----- > From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] > Sent: Wednesday, November 19, 2014 20:41 PM > To: Dexuan Cui > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; driverdev- > devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; > jasowang@xxxxxxxxxx; Haiyang Zhang > Subject: Re: [PATCH] tools: hv: ignore ENOBUFS in the KVP daemon > > Dexuan Cui <decui@xxxxxxxxxxxxx> writes: > > >> -----Original Message----- > >> From: Vitaly Kuznetsov > >> Sent: Wednesday, November 19, 2014 18:50 PM > >> To: Dexuan Cui > >> Cc: gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > driverdev- > >> devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; > >> jasowang@xxxxxxxxxx; 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) --- 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) { + syslog(LOG_ERR, "send error: ignored"); + continue; + } + exit(EXIT_FAILURE); } } Thanks, -- Dexuan _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
