ipv6: prevent fib6_run_gc() contention
commit 2ac3ac8f86f2fe065d746d9a9abaca867adec577 upstream.
On a high-traffic router with many processors and many IPv6 dst
entries, soft lockup in fib6_run_gc() can occur when number of
entries reaches gc_thresh.
This happens because fib6_run_gc() uses fib6_gc_lock to allow
only one thread to run the garbage collector but ip6_dst_gc()
doesn't update net->ipv6.ip6_rt_last_gc until fib6_run_gc()
returns. On a system with many entries, this can take some time
so that in the meantime, other threads pass the tests in
ip6_dst_gc() (ip6_rt_last_gc is still not updated) and wait for
the lock. They then have to run the garbage collector one after
another which blocks them for quite long.
Resolve this by replacing special value ~0UL of expire parameter
to fib6_run_gc() by explicit "force" parameter to choose between
spin_lock_bh() and spin_trylock_bh() and call fib6_run_gc() with
force=false if gc_thresh is reached but not max_size.
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>
diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 0ae759a..49c4cfe 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -266,7 +266,7 @@
struct nl_info *info);
extern void fib6_run_gc(unsigned long expires,
- struct net *net);
+ struct net *net, bool force);
extern void fib6_gc_cleanup(void);
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 2cfcfb7..fc5ce6e 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1593,19 +1593,16 @@
static DEFINE_SPINLOCK(fib6_gc_lock);
-void fib6_run_gc(unsigned long expires, struct net *net)
+void fib6_run_gc(unsigned long expires, struct net *net, bool force)
{
- if (expires != ~0UL) {
+ if (force) {
spin_lock_bh(&fib6_gc_lock);
- gc_args.timeout = expires ? (int)expires :
- net->ipv6.sysctl.ip6_rt_gc_interval;
- } else {
- if (!spin_trylock_bh(&fib6_gc_lock)) {
- mod_timer(&net->ipv6.ip6_fib_timer, jiffies + HZ);
- return;
- }
- gc_args.timeout = net->ipv6.sysctl.ip6_rt_gc_interval;
+ } else if (!spin_trylock_bh(&fib6_gc_lock)) {
+ mod_timer(&net->ipv6.ip6_fib_timer, jiffies + HZ);
+ return;
}
+ gc_args.timeout = expires ? (int)expires :
+ net->ipv6.sysctl.ip6_rt_gc_interval;
gc_args.more = icmp6_dst_gc();
@@ -1622,7 +1619,7 @@
static void fib6_gc_timer_cb(unsigned long arg)
{
- fib6_run_gc(0, (struct net *)arg);
+ fib6_run_gc(0, (struct net *)arg, true);
}
static int __net_init fib6_net_init(struct net *net)
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 3193a94..a1a9e7b 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1744,11 +1744,11 @@
switch (event) {
case NETDEV_CHANGEADDR:
neigh_changeaddr(&nd_tbl, dev);
- fib6_run_gc(~0UL, net);
+ fib6_run_gc(0, net, false);
break;
case NETDEV_DOWN:
neigh_ifdown(&nd_tbl, dev);
- fib6_run_gc(~0UL, net);
+ fib6_run_gc(0, net, false);
break;
case NETDEV_NOTIFY_PEERS:
ndisc_send_unsol_na(dev);
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index ec4d8e0..8ea2d77 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1245,7 +1245,7 @@
goto out;
net->ipv6.ip6_rt_gc_expire++;
- fib6_run_gc(net->ipv6.ip6_rt_gc_expire, net);
+ fib6_run_gc(net->ipv6.ip6_rt_gc_expire, net, entries > rt_max_size);
net->ipv6.ip6_rt_last_gc = now;
entries = dst_entries_get_slow(ops);
if (entries < ops->gc_thresh)
@@ -2841,7 +2841,7 @@
net = (struct net *)ctl->extra1;
delay = net->ipv6.sysctl.flush_delay;
proc_dointvec(ctl, write, buffer, lenp, ppos);
- fib6_run_gc(delay <= 0 ? ~0UL : (unsigned long)delay, net);
+ fib6_run_gc(delay <= 0 ? 0 : (unsigned long)delay, net, delay > 0);
return 0;
}