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[PATCH 3.2 103/107] ipv6: prevent fib6_run_gc() contention

From Ben Hutchings <ben@decadent.org.uk>
Newsgroups linux.kernel
Subject [PATCH 3.2 103/107] ipv6: prevent fib6_run_gc() contention
Date 2015-10-09 02:40 +0200
Message-ID <qhtT6-2Qh-59@gated-at.bofh.it> (permalink)
References <qhtzH-2tg-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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3.2.72-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Michal Kubeček <mkubecek@suse.cz>

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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
 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(-)

--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -217,7 +217,7 @@ extern void			inet6_rt_notify(int event,
 						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);
 
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1473,19 +1473,16 @@ static int fib6_age(struct rt6_info *rt,
 
 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,
 
 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)
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1743,11 +1743,11 @@ static int ndisc_netdev_event(struct not
 	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);
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1174,7 +1174,7 @@ static int ip6_dst_gc(struct dst_ops *op
 		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
 	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;
 }
 

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[PATCH 3.2 000/107] 3.2.72-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:30 +0200
  [PATCH 3.2 072/107] USB: option: add ZTE PIDs Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:30 +0200
  [PATCH 3.2 069/107] hfs,hfsplus: cache pages correctly between  bnode_create and bnode_free Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:30 +0200
  [PATCH 3.2 015/107] ocfs2: fix BUG in ocfs2_downconvert_thread_do_work() Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:30 +0200
  [PATCH 3.2 049/107] DRM - radeon: Don't link train DisplayPort on  HPD until we get the dpcd Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:30 +0200
  [PATCH 3.2 098/107] ipv6: lock socket in ip6_datagram_connect() Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:30 +0200
  [PATCH 3.2 024/107] libfc: Fix fc_fcp_cleanup_each_cmd() Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:30 +0200
  [PATCH 3.2 094/107] Initialize msg/shm IPC objects before doing  ipc_addid() Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 060/107] drm/i915: Always mark the object as dirty  when used by the GPU Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 047/107] eCryptfs: Invalidate dcache entries when  lower i_nlink is zero Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 009/107] target: REPORT LUNS should return LUN 0 even  for dynamic ACLs Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 095/107] net/tipc: initialize security state for new  connection  socket Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 018/107] x86/ldt: Make modify_ldt synchronous Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 036/107] PCI: Add VPD function 0 quirk for Intel  Ethernet devices Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 016/107] net: Clone skb before setting peeked flag Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 026/107] x86/ldt: Further fix FPU emulation Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 029/107] sparc64: Fix userspace FPU register corruptions. Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 023/107] libiscsi: Fix host busy blocking during  connection teardown Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 019/107] x86/ldt: Correct LDT access in single  stepping logic Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 017/107] net: Fix skb_set_peeked use-after-free bug Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 005/107] crypto: ixp4xx - Remove bogus BUG_ON on  scattered dst buffer Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 033/107] PCI: Fix TI816X class code quirk Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 051/107] rtlwifi: rtl8192cu: Add new device ID Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 032/107] [media] rc-core: fix remove uevent generation Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 068/107] powerpc/MSI: Fix race condition in tearing  down MSI interrupts Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 037/107] usb: gadget: m66592-udc: forever loop in  set_feature() Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 054/107] xfs: return errors from partial I/O failures  to files Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 103/107] ipv6: prevent fib6_run_gc() contention Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 044/107] serial: 8250: bind to ALi Fast Infrared  Controller (ALI5123) Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 070/107] hfs: fix B-tree corruption after insertion at  position 0 Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 050/107] rtlwifi: rtl8192cu: Add new device ID Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 048/107] xfs: Fix xfs_attr_leafblock definition Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 025/107] ipc,sem: fix use after free on IPC_RMID after  a task using same semaphore set exits Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 007/107] target/iscsi: Fix double free of a TUR  followed by a solicited NOPOUT Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:40 +0200
  [PATCH 3.2 081/107] usb: Use the USB_SS_MULT() macro to get the  burst multiplier. Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 079/107] s390/compat: correct uc_sigmask of the compat  signal frame Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 091/107] virtio-net: drop NETIF_F_FRAGLIST Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 053/107] drivercore: Fix unregistration path of  platform devices Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 006/107] USB: sierra: add 1199:68AB device ID Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 059/107] spi: spi-pxa2xx: Check status register to  determine if SSSR_TINT is disabled Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 002/107] pktgen: Require CONFIG_INET due to use of  IPv4 checksum function Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 085/107] cifs: use server timestamp for ntlmv2  authentication Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 066/107] ARM: 8429/1: disable GCC SRA optimization Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 061/107] Add radeon suspend/resume quirk for HP Compaq  dc5750. Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 046/107] USB: ftdi_sio: Added custom PID for  CustomWare products Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 013/107] perf: Fix fasync handling on inherited events Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 074/107] btrfs: skip waiting on ordered range for  special files Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 052/107] of/address: Don't loop forever in  of_find_matching_node_by_address(). Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 042/107] NFSv4: don't set SETATTR for O_RDONLY|O_EXCL Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 093/107] ipc/sem.c: fully initialize sem_array before  making it visible Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 039/107] auxdisplay: ks0108: fix refcount Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 083/107] usb: xhci: Clear XHCI_STATE_DYING on start Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 062/107] IB/uverbs: reject invalid or unknown opcodes Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 058/107] IB/uverbs: Fix race between ib_uverbs_open  and remove_one Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 102/107] perf tools: Fix build with perl 5.18 Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 075/107] ARM: 7880/1: Clear the IT state independent  of the Thumb-2 mode Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 105/107] parisc: Filter out spurious interrupts in  PA-RISC irq handler Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 100/107] net/ipv6: Correct PIM6 mrt_lock handling Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 030/107] dcache: Handle escaped paths in prepend_path Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 041/107] windfarm: decrement client count when  unregistering Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 076/107] ARM: fix Thumb2 signal handling when ARMv6 is  enabled Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 057/107] IB/mlx4: Use correct SL on AH query under RoCE Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 090/107] ipv6: addrconf: validate new MTU before  applying it Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 010/107] MIPS: Fix sched_getaffinity with MT FPAFF enabled Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 02:50 +0200
  [PATCH 3.2 063/107] Input: evdev - do not report errors form flush() Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 078/107] ASoC: fix broken pxa SoC support Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 064/107] crypto: ghash-clmulni: specify context size  for ghash async algorithm Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 065/107] fs: create and use seq_show_option for escaping Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 084/107] xhci: change xhci 1.0 only restrictions to  support xhci 1.1 Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 071/107] perf header: Fixup reading of HEADER_NRCPUS  feature Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 104/107] ipv6: update ip6_rt_last_gc every time GC is run Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 055/107] IB/qib: Change lkey table allocation to  support more MRs Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 073/107] Btrfs: fix read corruption of compressed and  shared extents Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  Re: [PATCH 3.2 000/107] 3.2.72-rc1 review Guenter Roeck <linux@roeck-us.net> - 2015-10-09 03:00 +0200
    Re: [PATCH 3.2 000/107] 3.2.72-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:20 +0200
  [PATCH 3.2 077/107] x86/platform: Fix Geode LX timekeeping in the  generic x86 build Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 087/107] ocfs2/dlm: fix deadlock when dispatch assert  master Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 056/107] SUNRPC: xs_reset_transport must mark the  connection as disconnected Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200
  [PATCH 3.2 082/107] xhci: give command abortion one more chance  before killing xhci Ben Hutchings <ben@decadent.org.uk> - 2015-10-09 03:00 +0200

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