On Wed, Jan 26, 2011 at 9:55 AM, Robert N. M. Watson <rwat...@freebsd.org> wrote: > > On 26 Jan 2011, at 17:12, m...@freebsd.org wrote: > >>> Hmm. Is this description missing mention of how wiring failures are >>> handled? (Also, it should probably mention that this call can sleep for >>> potentially quite long periods of time, even if sbuf_printf (and friends) >>> can't). >> >> I'm not sure how much to write, since some of the wiring failures are >> dealt with by the sysctl subsystem and are not documented. >> >> The current state of the actual code is that a failure in vslock(9) is >> ignored, unless it's ENOMEM in which case sysctl_wire_old_buffer sets >> the sysctl_req->validlen to 0, which would behave perhaps slightly >> unexpectedly for the user since no data will be copied out. >> >> Any non-ENOMEM failure from vslock() presumably would also have been a >> failure from SYSCTL_OUT and this does get squashed, perhaps >> incorrectly. >> >> I'll think about saving the error code so that sbuf_finish can report >> it if nothing else has gone wrong. > > Yeah, no specific opinions on the right answer, except perhaps that > sbuf_new_for_sysctl() > failing due to ENOMEM is something worth making it easy to report to the user.
The ENOMEM is already managed and squashed inside sysctl_wire_old_buffer(), so there's no way for sbuf_new_for_sysctl() to report it. It may end up happening automagically since it sets the validlen to 0. > I suppose an important question is now often we see this actually failing I don't believe we've ever seen a memory failure relating to sysctls at Isilon and we've been using the equivalent of this code for a few years. Our machines aren't low memory but they are under memory pressure sometimes. Thanks, matthew _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
