Revision fb59e9f1e9786635ea12e12bf6adbb132e10f979 authored by Hugh Dickins on 04 March 2008, 22:29:16 UTC, committed by Linus Torvalds on 05 March 2008, 00:35:15 UTC
While testing force_empty, during an exit_mmap, __mem_cgroup_remove_list called from mem_cgroup_uncharge_page oopsed on a NULL pointer in the lru list. I couldn't see what racing tasks on other cpus were doing, but surmise that another must have been in mem_cgroup_charge_common on the same page, between its unlock_page_cgroup and spin_lock_irqsave near done (thanks to that kzalloc which I'd almost changed to a kmalloc). Normally such a race cannot happen, the ref_cnt prevents it, the final uncharge cannot race with the initial charge. But force_empty buggers the ref_cnt, that's what it's all about; and thereafter forced pages are vulnerable to races such as this (just think of a shared page also mapped into an mm of another mem_cgroup than that just emptied). And remain vulnerable until they're freed indefinitely later. This patch just fixes the oops by moving the unlock_page_cgroups down below adding to and removing from the list (only possible given the previous patch); and while we're at it, we might as well make it an invariant that page->page_cgroup is always set while pc is on lru. But this behaviour of force_empty seems highly unsatisfactory to me: why have a ref_cnt if we always have to cope with it being violated (as in the earlier page migration patch). We may prefer force_empty to move pages to an orphan mem_cgroup (could be the root, but better not), from which other cgroups could recover them; we might need to reverse the locking again; but no time now for such concerns. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 9b3c0a0
File | Mode | Size |
---|---|---|
netfilter | ||
Kconfig | -rw-r--r-- | 5.3 KB |
Makefile | -rw-r--r-- | 1.3 KB |
addrconf.c | -rw-r--r-- | 105.4 KB |
addrconf_core.c | -rw-r--r-- | 2.4 KB |
addrlabel.c | -rw-r--r-- | 12.5 KB |
af_inet6.c | -rw-r--r-- | 22.9 KB |
ah6.c | -rw-r--r-- | 13.1 KB |
anycast.c | -rw-r--r-- | 12.1 KB |
datagram.c | -rw-r--r-- | 17.2 KB |
esp6.c | -rw-r--r-- | 13.6 KB |
exthdrs.c | -rw-r--r-- | 20.1 KB |
exthdrs_core.c | -rw-r--r-- | 3.2 KB |
fib6_rules.c | -rw-r--r-- | 6.4 KB |
icmp.c | -rw-r--r-- | 20.6 KB |
inet6_connection_sock.c | -rw-r--r-- | 6.2 KB |
inet6_hashtables.c | -rw-r--r-- | 6.6 KB |
ip6_fib.c | -rw-r--r-- | 29.8 KB |
ip6_flowlabel.c | -rw-r--r-- | 16.1 KB |
ip6_input.c | -rw-r--r-- | 6.2 KB |
ip6_output.c | -rw-r--r-- | 36.9 KB |
ip6_tunnel.c | -rw-r--r-- | 33.3 KB |
ipcomp6.c | -rw-r--r-- | 10.8 KB |
ipv6_sockglue.c | -rw-r--r-- | 23.8 KB |
mcast.c | -rw-r--r-- | 62.0 KB |
mip6.c | -rw-r--r-- | 13.2 KB |
ndisc.c | -rw-r--r-- | 43.8 KB |
netfilter.c | -rw-r--r-- | 3.4 KB |
proc.c | -rw-r--r-- | 8.4 KB |
protocol.c | -rw-r--r-- | 2.0 KB |
raw.c | -rw-r--r-- | 30.2 KB |
reassembly.c | -rw-r--r-- | 18.7 KB |
route.c | -rw-r--r-- | 59.3 KB |
sit.c | -rw-r--r-- | 21.3 KB |
sysctl_net_ipv6.c | -rw-r--r-- | 3.7 KB |
tcp_ipv6.c | -rw-r--r-- | 54.1 KB |
tunnel6.c | -rw-r--r-- | 4.3 KB |
udp.c | -rw-r--r-- | 25.4 KB |
udp_impl.h | -rw-r--r-- | 1.4 KB |
udplite.c | -rw-r--r-- | 3.1 KB |
xfrm6_input.c | -rw-r--r-- | 3.2 KB |
xfrm6_mode_beet.c | -rw-r--r-- | 2.9 KB |
xfrm6_mode_ro.c | -rw-r--r-- | 2.3 KB |
xfrm6_mode_transport.c | -rw-r--r-- | 2.3 KB |
xfrm6_mode_tunnel.c | -rw-r--r-- | 3.1 KB |
xfrm6_output.c | -rw-r--r-- | 2.1 KB |
xfrm6_policy.c | -rw-r--r-- | 7.4 KB |
xfrm6_state.c | -rw-r--r-- | 4.7 KB |
xfrm6_tunnel.c | -rw-r--r-- | 9.1 KB |
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...