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Fix deadlock when destroying VLANs.

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Synchronizing the epoch before freeing the multicast addresses while holding
the VLAN_XLOCK() might lead to a deadlock. Use deferred freeing of the VLAN
multicast addresses to resolve deadlock. Backtrace:

Thread1:
epoch_block_handler_preempt()
ck_epoch_synchronize_wait()
epoch_wait_preempt()
vlan_setmulti()
vlan_ioctl()
in6m_release_task()
gtaskqueue_run_locked()
gtaskqueue_thread_loop()
fork_exit()
fork_trampoline()

Thread2:
sleepq_switch()
sleepq_wait()
_sx_xlock_hard()
_sx_xlock()
in6_leavegroup()
in6_purgeaddr()
if_purgeaddrs()
if_detach_internal()
if_detach()
vlan_clone_destroy()
if_clone_destroyif()
if_clone_destroy()
ifioctl()
kern_ioctl()
sys_ioctl()
amd64_syscall()
fast_syscall_common()
syscall()

Differential revision:	https://reviews.freebsd.org/D17496
Reviewed by:		slavash, mmacy
Approved by:		re (kib)
Sponsored by:		Mellanox Technologies
This commit is contained in:
Hans Petter Selasky 2018-10-15 10:29:29 +00:00
parent 986368d85d
commit c32a9d66fb
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=339358
1 changed files with 10 additions and 4 deletions
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14
sys/net/if_vlan.c
View File

@ -153,6 +153,7 @@ struct ifvlantrunk {
struct vlan_mc_entry {
struct sockaddr_dl mc_addr;
CK_SLIST_ENTRY(vlan_mc_entry) mc_entries;
struct epoch_context mc_epoch_ctx;
};
struct ifvlan {
@ -316,6 +317,13 @@ VNET_DEFINE_STATIC(struct if_clone *, vlan_cloner);
#ifndef VLAN_ARRAY
#define HASH(n, m) ((((n) >> 8) ^ ((n) >> 4) ^ (n)) & (m))
static void
vlan_mc_free(struct epoch_context *ctx)
{
struct vlan_mc_entry *mc = __containerof(ctx, struct vlan_mc_entry, mc_epoch_ctx);
free(mc, M_VLAN);
}
static void
vlan_inithash(struct ifvlantrunk *trunk)
{
@ -572,8 +580,7 @@ vlan_setmulti(struct ifnet *ifp)
while ((mc = CK_SLIST_FIRST(&sc->vlan_mc_listhead)) != NULL) {
CK_SLIST_REMOVE_HEAD(&sc->vlan_mc_listhead, mc_entries);
(void)if_delmulti(ifp_p, (struct sockaddr *)&mc->mc_addr);
NET_EPOCH_WAIT();
free(mc, M_VLAN);
epoch_call(net_epoch_preempt, &mc->mc_epoch_ctx, vlan_mc_free);
}
/* Now program new ones. */
@ -1485,8 +1492,7 @@ vlan_unconfig_locked(struct ifnet *ifp, int departing)
error);
}
CK_SLIST_REMOVE_HEAD(&ifv->vlan_mc_listhead, mc_entries);
NET_EPOCH_WAIT();
free(mc, M_VLAN);
epoch_call(net_epoch_preempt, &mc->mc_epoch_ctx, vlan_mc_free);
}
vlan_setflags(ifp, 0); /* clear special flags on parent */