On Fri, May 2, 2014 at 3:08 PM, Alexander V. Chernikov <melif...@freebsd.org> wrote: > On 03.05.2014 00:22, Alan Somers wrote: >> On Fri, May 2, 2014 at 11:01 AM, Alexander V. Chernikov >> <melif...@freebsd.org> wrote: >>> On 02.05.2014 20:24, Alan Somers wrote: >>>> >>>> Author: asomers >>>> Date: Fri May 2 16:24:09 2014 >>>> New Revision: 265232 >>>> URL: http://svnweb.freebsd.org/changeset/base/265232 >>>> >>>> Log: >>>> Fix a panic caused by doing "ifconfig -am" while a lagg is being >>>> destroyed. >>>> The thread that is destroying the lagg has already set sc->sc_psc=NULL >>>> when >>>> the "ifconfig -am" thread gets to lacp_req(). It tries to dereference >>>> sc->sc_psc and panics. The solution is for lacp_req() to check the >>>> value of >>>> sc->sc_psc. If NULL, harmlessly return an lacp_opreq structure full of >>>> zeros. Full details in GNATS. >>> >>> Sorry, it looks like I've missed -net@ discussion. >> >> Thanks for the retroactive review; it's good too. >> >>> >>> While this patch minimizes panics, they still can occur. >>> If one thread performs lagg_clone_destroy() -> lagg_lacp_detach() (1) -> >>> lacp_detach(), executing >>> >>> struct lacp_softc *lsc = LACP_SOFTC(sc); (e.g. one line before sc_psc = NULL >>> assignment) >>> >>> At the same moment, another thread (initiated by ifconfig) executes >>> >>> >>> struct lacp_softc *lsc = LACP_SOFTC(sc); >>> >>> Then, thread #1 goes further to >>> >>> LACP_LOCK_DESTROY(lsc); >>> free(lsc, M_DEVBUF); >>> >>> After that, thread #2 performs >>> >>> bzero(req, sizeof(struct lacp_opreq)); >>> >>> passes lsc check for NULL and crashes on destroyed mutex. >>> >>> >>> Briefly looking, we can remove WUNLOCK() before lacp_detach() in >>> lagg_lacp_detach() (I'm unsure about the reasons why do we need unlock >>> here). >>> lacp_req() is already protected by at least LAGG_RLOCK() so we should get >>> consistent view of sc->sc_psc. >> >> The WUNLOCK was added in r168561 without comment. Removing it seems >> like it would work. It doesn't cause any new LORs or WITNESS >> warnings. And I can no longer reproduce the panic in lacp_req. >> However, it doesn't fix another panic in lagg_port_ioctl line 825 (my >> patch didn't either). Do you have any good ideas what to do about >> that? > Interesting. > Line numbers look a bit shifted. Is line 825 'LAGG_RUNLOCK(sc, &tracker)' ?
Yes. > > Are the steps to reproduce it the same as in kern/189003? Yes. BTW, In kern/189003, I suggested reverting 253687. In reality, I didn't revert it; I commented out the sysctl lines it added in lacp_attach(). > >> >> #9 0xffffffff808cee81 in __mtx_lock_sleep (c=0xfffff800052bb648, >> tid=18446735277704396800, opts=<value optimized out>, >> file=<value optimized out>, line=<value optimized out>) >> at /usr/home/alans/freebsd/head/sys/kern/kern_mutex.c:430 >> #10 0xffffffff808ced02 in __mtx_lock_flags (c=<value optimized out>, opts=0, >> file=0xffffffff80f6dd8c >> "/usr/home/alans/freebsd/head/sys/kern/kern_rmlock.c", line=407) at >> /usr/home/alans/freebsd/head/sys/kern/kern_mutex.c:223 >> #11 0xffffffff808e0032 in _rm_rlock (rm=0xfffff800052bb608, >> tracker=0xfffffe0097751918, trylock=<value optimized out>) >> at /usr/home/alans/freebsd/head/sys/kern/kern_rmlock.c:407 >> #12 0xffffffff808e0812 in _rm_rlock_debug (rm=0xfffff800052bb608, >> tracker=0xfffffe0097751918, trylock=0, >> file=0xffffffff81c1dd13 >> "/usr/home/alans/freebsd/head/sys/modules/if_lagg/../../net/if_lagg.c", >> line=825) >> at /usr/home/alans/freebsd/head/sys/kern/kern_rmlock.c:659 >> #13 0xffffffff81c19f62 in lagg_port_ioctl (ifp=0xfffff8000590d800, >> cmd=<value optimized out>, data=0xfffff80005582c00 "tap0") >> at >> /usr/home/alans/freebsd/head/sys/modules/if_lagg/../../net/if_lagg.c:825 >> #14 0xffffffff809ae407 in ifioctl (so=<value optimized out>, cmd=3225971084, >> data=0xfffff80005582c00 "tap0", td=<value optimized out>) >> at /usr/home/alans/freebsd/head/sys/net/if.c:2643 >> #15 0xffffffff8093b9fb in kern_ioctl (td=<value optimized out>, >> fd=<value optimized out>, com=<value optimized out>) at file.h:323 >> #16 0xffffffff8093b77c in sys_ioctl (td=0xfffff800053cc000, >> uap=0xfffffe0097751b80) >> at /usr/home/alans/freebsd/head/sys/kern/sys_generic.c:702 >> > _______________________________________________ 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"
