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)' ?
Are the steps to reproduce it the same as in kern/189003? > > #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"
