From 2491f0184830c5f1e1c794283177179937def4b7 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Michal=20Kube=C4=8Dek?= Date: Thu, 1 Aug 2013 10:04:14 +0200 Subject: [PATCH] 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 Signed-off-by: David S. Miller [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings Cc: Konstantin Khlebnikov --- include/net/ip6_fib.h | 2 +- net/ipv6/ip6_fib.c | 19 ++++++++----------- net/ipv6/ndisc.c | 4 ++-- net/ipv6/route.c | 4 ++-- 4 files changed, 13 insertions(+), 16 deletions(-) diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h index 5735a0f979c3..390735885629 100644 --- a/include/net/ip6_fib.h +++ b/include/net/ip6_fib.h @@ -217,7 +217,7 @@ extern void inet6_rt_notify(int event, struct rt6_info *rt, 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 ad62afcafa7c..ddedf6359920 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -1473,19 +1473,16 @@ static int fib6_age(struct rt6_info *rt, void *arg) 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(); @@ -1502,7 +1499,7 @@ void fib6_run_gc(unsigned long expires, struct net *net) 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 884d45fdf50f..39836dafa931 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1743,11 +1743,11 @@ static int ndisc_netdev_event(struct notifier_block *this, unsigned long event, 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 d89d1a63d270..716a711fc0f3 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1174,7 +1174,7 @@ static int ip6_dst_gc(struct dst_ops *ops) 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) @@ -2726,7 +2726,7 @@ int ipv6_sysctl_rtcache_flush(ctl_table *ctl, int write, 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; } -- 2.39.2