On 11/21/2016 06:41 PM, Lee Duncan wrote: > >> On Nov 21, 2016, at 6:14 AM, Hannes Reinecke <h...@suse.de >> <mailto:h...@suse.de>> wrote: >> >> On 11/19/2016 08:46 PM, The Lee-Man wrote: >>> In this wonderful new world of systemd, I have an issue with stopping >>> the iscsid service when the daemon has died or been killed. >>> >>> My setup: >>> * I have an iscsid.socket unit file, which is enabled and started >>> * I have an iscsid.service unit file, which controls the iscsid daemon. >>> This is disabled and not started >>> >>> Normally, if I run a command like "iscsiadm -m discovery -t st -p >>> SOME-TARGET", systemd notices that iscsiadm is trying to talk to iscsid >>> through the socket, and it starts up iscsid. This is the cool part >>> (IMHO) of systemd socket activation. >>> >>> When I want to stop iscsid, I can just tell systemctl to do it via >>> "systemctl stop iscsid", and it runs the "ExecStop=" command in the >>> service unit file, which is "iscsiadm -k 0 2" before terminating the >>> daemon process(es). >>> >>> [NOTE: the "2" here in this command actually does nothing and is >>> ignored, but I copied this from someplace else long ago, and the "2" was >>> present there.] >>> >>> It is of importance, in this case, that the ExecStop command actually >>> sends an IPC message to the daemon (iscsid) requesting it to cleanly >>> shut itself down. Herein lies the rub. >>> >>> All of this works great until the daemon happens not to be running. You >>> can simulate this with "kill -TERM $(pidof iscsid)" when the daemon is >>> running. Now you are in a situation where systemd started the service >>> and knows it is now not running, so it seems to send the ExecStop >>> command to cleanly shut it down. This command hangs! It seems to be >>> stuck in an infinite loop trying to send the shutdown command to the >>> daemon, waiting for it to timeout, then trying again. The daemon starts >>> up, sees an IPC error, and exits. >>> >>> While this clearly seems like a systemd issue, I have found a workaround >>> that looks clean. Well, as clean as the shutdown command is, anyway. >> >> No, that's not the case. >> This is a plain issue with iscsiadm; it's waiting in 'recv' to receive >> an response packet from iscsid which of course never will come. >> The reason why this becomes an issue now is that systemd holds the >> socket for us, so the socket is available; hence 'recv()' will not >> return with ENOTCONN or somesuch, indicating that the socket isn't >> present. >> The socket _is_ present, it's just not sending any responses back. >> >> Attached is a patch for open-iscsi to use 'poll()' before recv(), and >> terminating it if we didn't get a response in time. >> >> This doesn't do anything from the mentioned socket activation issue for >> iscsid, but at least iscsiadm doesn't hang anymore. >> >> Cheers, >> >> Hannes > > One issue with the patch. It looks like you might need a “break” added > after the “log_error()” when poll() fails, or it could be an infinite loop: > > +while (len) { > +struct pollfd pfd; > + > +pfd.fd = fd; > +pfd.events = POLLIN; > +err = poll(&pfd, 1, timeout); > +if (!err) { > +if (poll_wait) > +continue; > +return ISCSI_ERR_ISCSID_NOTCONN; > +} else if (err < 0) { > +if (errno == EINTR) > +continue; > +log_error("got poll error (%d/%d), daemon died?", > + err, errno); > +return ISCSI_ERR_ISCSID_COMM_ERR; > +} else if (!pfd.revents & POLLIN) > +continue; > +err = recv(fd, rsp, sizeof(*rsp), MSG_WAITALL); > +if (err < 0) { > +log_error("got read error (%d/%d), daemon died?", > + err, errno); > break; > <<===== Add a break here? > +} else { > +len -= err; > +iscsi_err = rsp->err; > +} > +} > > I can make that adjustment, if you agree it’s needed, when applying the > patch. > Yeah, you are correct. Please fix it up while you're at it.
Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking h...@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg) -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to open-iscsi+unsubscr...@googlegroups.com. To post to this group, send email to open-iscsi@googlegroups.com. Visit this group at https://groups.google.com/group/open-iscsi. For more options, visit https://groups.google.com/d/optout.
