Dexuan Cui <decui@xxxxxxxxxxxxx> writes: >> -----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) > 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 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
