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lagg: Avoid adding a port to a lagg device being destroyed.

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The lagg_clone_destroy() handles detach and waiting for ifconfig callers
to drain already.

This narrows the race for 2 panics that the tests triggered. Both were a
consequence of adding a port to the lagg device after it had already detached
from all of its ports. The link state task would run after lagg_clone_destroy()
free'd the lagg softc.

    kernel:trap_fatal+0xa4
    kernel:trap_pfault+0x61
    kernel:trap+0x316
    kernel:witness_checkorder+0x6d
    kernel:_sx_xlock+0x72
    if_lagg.ko:lagg_port_state+0x3b
    kernel:if_down+0x144
    kernel:if_detach+0x659
    if_tap.ko:tap_destroy+0x46
    kernel:if_clone_destroyif+0x1b7
    kernel:if_clone_destroy+0x8d
    kernel:ifioctl+0x29c
    kernel:kern_ioctl+0x2bd
    kernel:sys_ioctl+0x16d
    kernel:amd64_syscall+0x337

    kernel:trap_fatal+0xa4
    kernel:trap_pfault+0x61
    kernel:trap+0x316
    kernel:witness_checkorder+0x6d
    kernel:_sx_xlock+0x72
    if_lagg.ko:lagg_port_state+0x3b
    kernel:do_link_state_change+0x9b
    kernel:taskqueue_run_locked+0x10b
    kernel:taskqueue_run+0x49
    kernel:ithread_loop+0x19c
    kernel:fork_exit+0x83

PR:		244168
Reviewed by:	markj
MFC after:	2 weeks
Sponsored by:	Dell EMC
Differential Revision:	https://reviews.freebsd.org/D25284
This commit is contained in:
Bryan Drewery 2020-08-13 22:06:27 +00:00
parent 8a0edc914f
commit 3869d41465
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=364220
1 changed files with 5 additions and 0 deletions
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5
sys/net/if_lagg.c
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@ -679,6 +679,9 @@ lagg_port_create(struct lagg_softc *sc, struct ifnet *ifp)
return (EINVAL);
}
if (sc->sc_destroying == 1)
return (ENXIO);
/* Limit the maximal number of lagg ports */
if (sc->sc_count >= LAGG_MAX_PORTS)
return (ENOSPC);
@ -1191,6 +1194,8 @@ lagg_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
bzero(&rpbuf, sizeof(rpbuf));
/* XXX: This can race with lagg_clone_destroy. */
switch (cmd) {
case SIOCGLAGG:
LAGG_XLOCK(sc);