<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/mm/memcontrol.c, branch v3.3</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>memcg: free mem_cgroup by RCU to fix oops</title>
<updated>2012-03-16T00:03:03+00:00</updated>
<author>
<name>Hugh Dickins</name>
<email>hughd@google.com</email>
</author>
<published>2012-03-15T22:17:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=59927fb984de1703c67bc640c3e522d8b5276c73'/>
<id>59927fb984de1703c67bc640c3e522d8b5276c73</id>
<content type='text'>
After fixing the GPF in mem_cgroup_lru_del_list(), three times one
machine running a similar load (moving and removing memcgs while
swapping) has oopsed in mem_cgroup_zone_nr_lru_pages(), when retrieving
memcg zone numbers for get_scan_count() for shrink_mem_cgroup_zone():
this is where a struct mem_cgroup is first accessed after being chosen
by mem_cgroup_iter().

Just what protects a struct mem_cgroup from being freed, in between
mem_cgroup_iter()'s css_get_next() and its css_tryget()? css_tryget()
fails once css-&gt;refcnt is zero with CSS_REMOVED set in flags, yes: but
what if that memory is freed and reused for something else, which sets
"refcnt" non-zero? Hmm, and scope for an indefinite freeze if refcnt is
left at zero but flags are cleared.

It's tempting to move the css_tryget() into css_get_next(), to make it
really "get" the css, but I don't think that actually solves anything:
the same difficulty in moving from css_id found to stable css remains.

But we already have rcu_read_lock() around the two, so it's easily fixed
if __mem_cgroup_free() just uses kfree_rcu() to free mem_cgroup.

However, a big struct mem_cgroup is allocated with vzalloc() instead of
kzalloc(), and we're not allowed to vfree() at interrupt time: there
doesn't appear to be a general vfree_rcu() to help with this, so roll
our own using schedule_work().  The compiler decently removes
vfree_work() and vfree_rcu() when the config doesn't need them.

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Acked-by: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Acked-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Cc: Konstantin Khlebnikov &lt;khlebnikov@openvz.org&gt;
Cc: Tejun Heo &lt;tj@kernel.org&gt;
Cc: Ying Han &lt;yinghan@google.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
After fixing the GPF in mem_cgroup_lru_del_list(), three times one
machine running a similar load (moving and removing memcgs while
swapping) has oopsed in mem_cgroup_zone_nr_lru_pages(), when retrieving
memcg zone numbers for get_scan_count() for shrink_mem_cgroup_zone():
this is where a struct mem_cgroup is first accessed after being chosen
by mem_cgroup_iter().

Just what protects a struct mem_cgroup from being freed, in between
mem_cgroup_iter()'s css_get_next() and its css_tryget()? css_tryget()
fails once css-&gt;refcnt is zero with CSS_REMOVED set in flags, yes: but
what if that memory is freed and reused for something else, which sets
"refcnt" non-zero? Hmm, and scope for an indefinite freeze if refcnt is
left at zero but flags are cleared.

It's tempting to move the css_tryget() into css_get_next(), to make it
really "get" the css, but I don't think that actually solves anything:
the same difficulty in moving from css_id found to stable css remains.

But we already have rcu_read_lock() around the two, so it's easily fixed
if __mem_cgroup_free() just uses kfree_rcu() to free mem_cgroup.

However, a big struct mem_cgroup is allocated with vzalloc() instead of
kzalloc(), and we're not allowed to vfree() at interrupt time: there
doesn't appear to be a general vfree_rcu() to help with this, so roll
our own using schedule_work().  The compiler decently removes
vfree_work() and vfree_rcu() when the config doesn't need them.

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Acked-by: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Acked-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Cc: Konstantin Khlebnikov &lt;khlebnikov@openvz.org&gt;
Cc: Tejun Heo &lt;tj@kernel.org&gt;
Cc: Ying Han &lt;yinghan@google.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>memcg: revert fix to mapcount check for this release</title>
<updated>2012-03-09T23:32:20+00:00</updated>
<author>
<name>Hugh Dickins</name>
<email>hughd@google.com</email>
</author>
<published>2012-03-09T21:37:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=be22aece684f5a700e6247b9861c3759d5798a3c'/>
<id>be22aece684f5a700e6247b9861c3759d5798a3c</id>
<content type='text'>
Respectfully revert commit e6ca7b89dc76 "memcg: fix mapcount check
in move charge code for anonymous page" for the 3.3 release, so that
it behaves exactly like releases 2.6.35 through 3.2 in this respect.

Horiguchi-san's commit is correct in itself, 1 makes much more sense
than 2 in that check; but it does not go far enough - swapcount
should be considered too - if we really want such a check at all.

We appear to have reached agreement now, and expect that 3.4 will
remove the mapcount check, but had better not make 3.3 different.

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Reviewed-by: Naoya Horiguchi &lt;n-horiguchi@ah.jp.nec.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Respectfully revert commit e6ca7b89dc76 "memcg: fix mapcount check
in move charge code for anonymous page" for the 3.3 release, so that
it behaves exactly like releases 2.6.35 through 3.2 in this respect.

Horiguchi-san's commit is correct in itself, 1 makes much more sense
than 2 in that check; but it does not go far enough - swapcount
should be considered too - if we really want such a check at all.

We appear to have reached agreement now, and expect that 3.4 will
remove the mapcount check, but had better not make 3.3 different.

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Reviewed-by: Naoya Horiguchi &lt;n-horiguchi@ah.jp.nec.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>memcg: fix mapcount check in move charge code for anonymous page</title>
<updated>2012-03-05T23:49:43+00:00</updated>
<author>
<name>Naoya Horiguchi</name>
<email>n-horiguchi@ah.jp.nec.com</email>
</author>
<published>2012-03-05T22:59:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=e6ca7b89dc76abf77c80887fed54e0a60c87c0a8'/>
<id>e6ca7b89dc76abf77c80887fed54e0a60c87c0a8</id>
<content type='text'>
Currently the charge on shared anonyous pages is supposed not to moved in
task migration.  To implement this, we need to check that mapcount &gt; 1,
instread of &gt; 2.  So this patch fixes it.

Signed-off-by: Naoya Horiguchi &lt;n-horiguchi@ah.jp.nec.com&gt;
Reviewed-by: Daisuke Nishimura &lt;nishimura@mxp.nes.nec.co.jp&gt;
Cc: Andrea Arcangeli &lt;aarcange@redhat.com&gt;
Cc: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Cc: Hillf Danton &lt;dhillf@gmail.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Currently the charge on shared anonyous pages is supposed not to moved in
task migration.  To implement this, we need to check that mapcount &gt; 1,
instread of &gt; 2.  So this patch fixes it.

Signed-off-by: Naoya Horiguchi &lt;n-horiguchi@ah.jp.nec.com&gt;
Reviewed-by: Daisuke Nishimura &lt;nishimura@mxp.nes.nec.co.jp&gt;
Cc: Andrea Arcangeli &lt;aarcange@redhat.com&gt;
Cc: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Cc: Hillf Danton &lt;dhillf@gmail.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>memcg: fix GPF when cgroup removal races with last exit</title>
<updated>2012-03-05T23:49:43+00:00</updated>
<author>
<name>Hugh Dickins</name>
<email>hughd@google.com</email>
</author>
<published>2012-03-05T22:59:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7512102cf64d36e3c7444480273623c7aab3563f'/>
<id>7512102cf64d36e3c7444480273623c7aab3563f</id>
<content type='text'>
When moving tasks from old memcg (with move_charge_at_immigrate on new
memcg), followed by removal of old memcg, hit General Protection Fault in
mem_cgroup_lru_del_list() (called from release_pages called from
free_pages_and_swap_cache from tlb_flush_mmu from tlb_finish_mmu from
exit_mmap from mmput from exit_mm from do_exit).

Somewhat reproducible, takes a few hours: the old struct mem_cgroup has
been freed and poisoned by SLAB_DEBUG, but mem_cgroup_lru_del_list() is
still trying to update its stats, and take page off lru before freeing.

A task, or a charge, or a page on lru: each secures a memcg against
removal.  In this case, the last task has been moved out of the old memcg,
and it is exiting: anonymous pages are uncharged one by one from the
memcg, as they are zapped from its pagetables, so the charge gets down to
0; but the pages themselves are queued in an mmu_gather for freeing.

Most of those pages will be on lru (and force_empty is careful to
lru_add_drain_all, to add pages from pagevec to lru first), but not
necessarily all: perhaps some have been isolated for page reclaim, perhaps
some isolated for other reasons.  So, force_empty may find no task, no
charge and no page on lru, and let the removal proceed.

There would still be no problem if these pages were immediately freed; but
typically (and the put_page_testzero protocol demands it) they have to be
added back to lru before they are found freeable, then removed from lru
and freed.  We don't see the issue when adding, because the
mem_cgroup_iter() loops keep their own reference to the memcg being
scanned; but when it comes to mem_cgroup_lru_del_list().

I believe this was not an issue in v3.2: there, PageCgroupAcctLRU and
PageCgroupUsed flags were used (like a trick with mirrors) to deflect view
of pc-&gt;mem_cgroup to the stable root_mem_cgroup when neither set.
38c5d72f3ebe ("memcg: simplify LRU handling by new rule") mercifully
removed those convolutions, but left this General Protection Fault.

But it's surprisingly easy to restore the old behaviour: just check
PageCgroupUsed in mem_cgroup_lru_add_list() (which decides on which lruvec
to add), and reset pc to root_mem_cgroup if page is uncharged.  A risky
change?  just going back to how it worked before; testing, and an audit of
uses of pc-&gt;mem_cgroup, show no problem.

And there's a nice bonus: with mem_cgroup_lru_add_list() itself making
sure that an uncharged page goes to root lru, mem_cgroup_reset_owner() no
longer has any purpose, and we can safely revert 4e5f01c2b9b9 ("memcg:
clear pc-&gt;mem_cgroup if necessary").

Calling update_page_reclaim_stat() after add_page_to_lru_list() in swap.c
is not strictly necessary: the lru_lock there, with RCU before memcg
structures are freed, makes mem_cgroup_get_reclaim_stat_from_page safe
without that; but it seems cleaner to rely on one dependency less.

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Cc: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Cc: Konstantin Khlebnikov &lt;khlebnikov@openvz.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When moving tasks from old memcg (with move_charge_at_immigrate on new
memcg), followed by removal of old memcg, hit General Protection Fault in
mem_cgroup_lru_del_list() (called from release_pages called from
free_pages_and_swap_cache from tlb_flush_mmu from tlb_finish_mmu from
exit_mmap from mmput from exit_mm from do_exit).

Somewhat reproducible, takes a few hours: the old struct mem_cgroup has
been freed and poisoned by SLAB_DEBUG, but mem_cgroup_lru_del_list() is
still trying to update its stats, and take page off lru before freeing.

A task, or a charge, or a page on lru: each secures a memcg against
removal.  In this case, the last task has been moved out of the old memcg,
and it is exiting: anonymous pages are uncharged one by one from the
memcg, as they are zapped from its pagetables, so the charge gets down to
0; but the pages themselves are queued in an mmu_gather for freeing.

Most of those pages will be on lru (and force_empty is careful to
lru_add_drain_all, to add pages from pagevec to lru first), but not
necessarily all: perhaps some have been isolated for page reclaim, perhaps
some isolated for other reasons.  So, force_empty may find no task, no
charge and no page on lru, and let the removal proceed.

There would still be no problem if these pages were immediately freed; but
typically (and the put_page_testzero protocol demands it) they have to be
added back to lru before they are found freeable, then removed from lru
and freed.  We don't see the issue when adding, because the
mem_cgroup_iter() loops keep their own reference to the memcg being
scanned; but when it comes to mem_cgroup_lru_del_list().

I believe this was not an issue in v3.2: there, PageCgroupAcctLRU and
PageCgroupUsed flags were used (like a trick with mirrors) to deflect view
of pc-&gt;mem_cgroup to the stable root_mem_cgroup when neither set.
38c5d72f3ebe ("memcg: simplify LRU handling by new rule") mercifully
removed those convolutions, but left this General Protection Fault.

But it's surprisingly easy to restore the old behaviour: just check
PageCgroupUsed in mem_cgroup_lru_add_list() (which decides on which lruvec
to add), and reset pc to root_mem_cgroup if page is uncharged.  A risky
change?  just going back to how it worked before; testing, and an audit of
uses of pc-&gt;mem_cgroup, show no problem.

And there's a nice bonus: with mem_cgroup_lru_add_list() itself making
sure that an uncharged page goes to root lru, mem_cgroup_reset_owner() no
longer has any purpose, and we can safely revert 4e5f01c2b9b9 ("memcg:
clear pc-&gt;mem_cgroup if necessary").

Calling update_page_reclaim_stat() after add_page_to_lru_list() in swap.c
is not strictly necessary: the lru_lock there, with RCU before memcg
structures are freed, makes mem_cgroup_get_reclaim_stat_from_page safe
without that; but it seems cleaner to rely on one dependency less.

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Cc: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Cc: Konstantin Khlebnikov &lt;khlebnikov@openvz.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>memcg: fix deadlock by inverting lrucare nesting</title>
<updated>2012-03-05T23:49:43+00:00</updated>
<author>
<name>Hugh Dickins</name>
<email>hughd@google.com</email>
</author>
<published>2012-03-05T22:59:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=9ce70c0240d01309b34712f87eda4fbfba3c3764'/>
<id>9ce70c0240d01309b34712f87eda4fbfba3c3764</id>
<content type='text'>
We have forgotten the rules of lock nesting: the irq-safe ones must be
taken inside the non-irq-safe ones, otherwise we are open to deadlock:

CPU0                          CPU1
----                          ----
lock(&amp;(&amp;pc-&gt;lock)-&gt;rlock);
                              local_irq_disable();
                              lock(&amp;(&amp;zone-&gt;lru_lock)-&gt;rlock);
                              lock(&amp;(&amp;pc-&gt;lock)-&gt;rlock);
&lt;Interrupt&gt;
lock(&amp;(&amp;zone-&gt;lru_lock)-&gt;rlock);

To check a different locking issue, I happened to add a spin_lock to
memcg's bit_spin_lock in lock_page_cgroup(), and lockdep very quickly
complained about __mem_cgroup_commit_charge_lrucare() (on CPU1 above).

So delete __mem_cgroup_commit_charge_lrucare(), passing a bool lrucare to
__mem_cgroup_commit_charge() instead, taking zone-&gt;lru_lock under
lock_page_cgroup() in the lrucare case.

The original was using spin_lock_irqsave, but we'd be in more trouble if
it were ever called at interrupt time: unconditional _irq is enough.  And
ClearPageLRU before del from lru, SetPageLRU before add to lru: no strong
reason, but that is the ordering used consistently elsewhere.

Fixes 36b62ad539498d00c2d280a151a ("memcg: simplify corner case handling
of LRU").

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Acked-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Cc: Konstantin Khlebnikov &lt;khlebnikov@openvz.org&gt;
Acked-by: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
We have forgotten the rules of lock nesting: the irq-safe ones must be
taken inside the non-irq-safe ones, otherwise we are open to deadlock:

CPU0                          CPU1
----                          ----
lock(&amp;(&amp;pc-&gt;lock)-&gt;rlock);
                              local_irq_disable();
                              lock(&amp;(&amp;zone-&gt;lru_lock)-&gt;rlock);
                              lock(&amp;(&amp;pc-&gt;lock)-&gt;rlock);
&lt;Interrupt&gt;
lock(&amp;(&amp;zone-&gt;lru_lock)-&gt;rlock);

To check a different locking issue, I happened to add a spin_lock to
memcg's bit_spin_lock in lock_page_cgroup(), and lockdep very quickly
complained about __mem_cgroup_commit_charge_lrucare() (on CPU1 above).

So delete __mem_cgroup_commit_charge_lrucare(), passing a bool lrucare to
__mem_cgroup_commit_charge() instead, taking zone-&gt;lru_lock under
lock_page_cgroup() in the lrucare case.

The original was using spin_lock_irqsave, but we'd be in more trouble if
it were ever called at interrupt time: unconditional _irq is enough.  And
ClearPageLRU before del from lru, SetPageLRU before add to lru: no strong
reason, but that is the ordering used consistently elsewhere.

Fixes 36b62ad539498d00c2d280a151a ("memcg: simplify corner case handling
of LRU").

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Acked-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Cc: Konstantin Khlebnikov &lt;khlebnikov@openvz.org&gt;
Acked-by: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mm: memcg: Correct unregistring of events attached to the same eventfd</title>
<updated>2012-02-24T16:55:51+00:00</updated>
<author>
<name>Anton Vorontsov</name>
<email>anton.vorontsov@linaro.org</email>
</author>
<published>2012-02-24T01:14:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=371528caec553785c37f73fa3926ea0de84f986f'/>
<id>371528caec553785c37f73fa3926ea0de84f986f</id>
<content type='text'>
There is an issue when memcg unregisters events that were attached to
the same eventfd:

- On the first call mem_cgroup_usage_unregister_event() removes all
  events attached to a given eventfd, and if there were no events left,
  thresholds-&gt;primary would become NULL;

- Since there were several events registered, cgroups core will call
  mem_cgroup_usage_unregister_event() again, but now kernel will oops,
  as the function doesn't expect that threshold-&gt;primary may be NULL.

That's a good question whether mem_cgroup_usage_unregister_event()
should actually remove all events in one go, but nowadays it can't
do any better as cftype-&gt;unregister_event callback doesn't pass
any private event-associated cookie. So, let's fix the issue by
simply checking for threshold-&gt;primary.

FWIW, w/o the patch the following oops may be observed:

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
 IP: [&lt;ffffffff810be32c&gt;] mem_cgroup_usage_unregister_event+0x9c/0x1f0
 Pid: 574, comm: kworker/0:2 Not tainted 3.3.0-rc4+ #9 Bochs Bochs
 RIP: 0010:[&lt;ffffffff810be32c&gt;]  [&lt;ffffffff810be32c&gt;] mem_cgroup_usage_unregister_event+0x9c/0x1f0
 RSP: 0018:ffff88001d0b9d60  EFLAGS: 00010246
 Process kworker/0:2 (pid: 574, threadinfo ffff88001d0b8000, task ffff88001de91cc0)
 Call Trace:
  [&lt;ffffffff8107092b&gt;] cgroup_event_remove+0x2b/0x60
  [&lt;ffffffff8103db94&gt;] process_one_work+0x174/0x450
  [&lt;ffffffff8103e413&gt;] worker_thread+0x123/0x2d0

Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Anton Vorontsov &lt;anton.vorontsov@linaro.org&gt;
Acked-by: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Cc: Kirill A. Shutemov &lt;kirill@shutemov.name&gt;
Cc: Michal Hocko &lt;mhocko@suse.cz&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There is an issue when memcg unregisters events that were attached to
the same eventfd:

- On the first call mem_cgroup_usage_unregister_event() removes all
  events attached to a given eventfd, and if there were no events left,
  thresholds-&gt;primary would become NULL;

- Since there were several events registered, cgroups core will call
  mem_cgroup_usage_unregister_event() again, but now kernel will oops,
  as the function doesn't expect that threshold-&gt;primary may be NULL.

That's a good question whether mem_cgroup_usage_unregister_event()
should actually remove all events in one go, but nowadays it can't
do any better as cftype-&gt;unregister_event callback doesn't pass
any private event-associated cookie. So, let's fix the issue by
simply checking for threshold-&gt;primary.

FWIW, w/o the patch the following oops may be observed:

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
 IP: [&lt;ffffffff810be32c&gt;] mem_cgroup_usage_unregister_event+0x9c/0x1f0
 Pid: 574, comm: kworker/0:2 Not tainted 3.3.0-rc4+ #9 Bochs Bochs
 RIP: 0010:[&lt;ffffffff810be32c&gt;]  [&lt;ffffffff810be32c&gt;] mem_cgroup_usage_unregister_event+0x9c/0x1f0
 RSP: 0018:ffff88001d0b9d60  EFLAGS: 00010246
 Process kworker/0:2 (pid: 574, threadinfo ffff88001d0b8000, task ffff88001de91cc0)
 Call Trace:
  [&lt;ffffffff8107092b&gt;] cgroup_event_remove+0x2b/0x60
  [&lt;ffffffff8103db94&gt;] process_one_work+0x174/0x450
  [&lt;ffffffff8103e413&gt;] worker_thread+0x123/0x2d0

Cc: stable &lt;stable@vger.kernel.org&gt;
Signed-off-by: Anton Vorontsov &lt;anton.vorontsov@linaro.org&gt;
Acked-by: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Cc: Kirill A. Shutemov &lt;kirill@shutemov.name&gt;
Cc: Michal Hocko &lt;mhocko@suse.cz&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>mm/memcontrol.c: fix warning with CONFIG_NUMA=n</title>
<updated>2012-02-04T00:16:40+00:00</updated>
<author>
<name>Andrew Morton</name>
<email>akpm@linux-foundation.org</email>
</author>
<published>2012-02-03T23:37:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=82b3f2a7171731cce62f25058d25afb91a14710c'/>
<id>82b3f2a7171731cce62f25058d25afb91a14710c</id>
<content type='text'>
mm/memcontrol.c: In function 'memcg_check_events':
mm/memcontrol.c:779: warning: unused variable 'do_numainfo'

Acked-by: Michal Hocko &lt;mhocko@suse.cz&gt;
Cc: Li Zefan &lt;lizf@cn.fujitsu.com&gt;
Cc: Hiroyuki KAMEZAWA &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Acked-by: "Kirill A. Shutemov" &lt;kirill@shutemov.name&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
mm/memcontrol.c: In function 'memcg_check_events':
mm/memcontrol.c:779: warning: unused variable 'do_numainfo'

Acked-by: Michal Hocko &lt;mhocko@suse.cz&gt;
Cc: Li Zefan &lt;lizf@cn.fujitsu.com&gt;
Cc: Hiroyuki KAMEZAWA &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Cc: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Acked-by: "Kirill A. Shutemov" &lt;kirill@shutemov.name&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net</title>
<updated>2012-01-24T23:51:40+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2012-01-24T23:51:40+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=701b259f446be2f3625fb852bceb93afe76e206d'/>
<id>701b259f446be2f3625fb852bceb93afe76e206d</id>
<content type='text'>
Davem says:

1) Fix JIT code generation on x86-64 for divide by zero, from Eric Dumazet.

2) tg3 header length computation correction from Eric Dumazet.

3) More build and reference counting fixes for socket memory cgroup
   code from Glauber Costa.

4) module.h snuck back into a core header after all the hard work we
   did to remove that, from Paul Gortmaker and Jesper Dangaard Brouer.

5) Fix PHY naming regression and add some new PCI IDs in stmmac, from
   Alessandro Rubini.

6) Netlink message generation fix in new team driver, should only advertise
   the entries that changed during events, from Jiri Pirko.

7) SRIOV VF registration and unregistration fixes, and also add a
   missing PCI ID, from Roopa Prabhu.

8) Fix infinite loop in tx queue flush code of brcmsmac, from Stanislaw Gruszka.

9) ftgmac100/ftmac100 build fix, missing interrupt.h include.

10) Memory leak fix in net/hyperv do_set_mutlicast() handling, from Wei Yongjun.

11) Off by one fix in netem packet scheduler, from Vijay Subramanian.

12) TCP loss detection fix from Yuchung Cheng.

13) TCP reset packet MD5 calculation uses wrong address, fix from Shawn Lu.

14) skge carrier assertion and DMA mapping fixes from Stephen Hemminger.

15) Congestion recovery undo performed at the wrong spot in BIC and CUBIC
    congestion control modules, fix from Neal Cardwell.

16) Ethtool ETHTOOL_GSSET_INFO is unnecessarily restrictive, from Michał Mirosław.

17) Fix triggerable race in ipv6 sysctl handling, from Francesco Ruggeri.

18) Statistics bug fixes in mlx4 from Eugenia Emantayev.

19) rds locking bug fix during info dumps, from your's truly.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (67 commits)
  rds: Make rds_sock_lock BH rather than IRQ safe.
  netprio_cgroup.h: dont include module.h from other includes
  net: flow_dissector.c missing include linux/export.h
  team: send only changed options/ports via netlink
  net/hyperv: fix possible memory leak in do_set_multicast()
  drivers/net: dsa/mv88e6xxx.c files need linux/module.h
  stmmac: added PCI identifiers
  llc: Fix race condition in llc_ui_recvmsg
  stmmac: fix phy naming inconsistency
  dsa: Add reporting of silicon revision for Marvell 88E6123/88E6161/88E6165 switches.
  tg3: fix ipv6 header length computation
  skge: add byte queue limit support
  mv643xx_eth: Add Rx Discard and Rx Overrun statistics
  bnx2x: fix compilation error with SOE in fw_dump
  bnx2x: handle CHIP_REVISION during init_one
  bnx2x: allow user to change ring size in ISCSI SD mode
  bnx2x: fix Big-Endianess in ethtool -t
  bnx2x: fixed ethtool statistics for MF modes
  bnx2x: credit-leakage fixup on vlan_mac_del_all
  macvlan: fix a possible use after free
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Davem says:

1) Fix JIT code generation on x86-64 for divide by zero, from Eric Dumazet.

2) tg3 header length computation correction from Eric Dumazet.

3) More build and reference counting fixes for socket memory cgroup
   code from Glauber Costa.

4) module.h snuck back into a core header after all the hard work we
   did to remove that, from Paul Gortmaker and Jesper Dangaard Brouer.

5) Fix PHY naming regression and add some new PCI IDs in stmmac, from
   Alessandro Rubini.

6) Netlink message generation fix in new team driver, should only advertise
   the entries that changed during events, from Jiri Pirko.

7) SRIOV VF registration and unregistration fixes, and also add a
   missing PCI ID, from Roopa Prabhu.

8) Fix infinite loop in tx queue flush code of brcmsmac, from Stanislaw Gruszka.

9) ftgmac100/ftmac100 build fix, missing interrupt.h include.

10) Memory leak fix in net/hyperv do_set_mutlicast() handling, from Wei Yongjun.

11) Off by one fix in netem packet scheduler, from Vijay Subramanian.

12) TCP loss detection fix from Yuchung Cheng.

13) TCP reset packet MD5 calculation uses wrong address, fix from Shawn Lu.

14) skge carrier assertion and DMA mapping fixes from Stephen Hemminger.

15) Congestion recovery undo performed at the wrong spot in BIC and CUBIC
    congestion control modules, fix from Neal Cardwell.

16) Ethtool ETHTOOL_GSSET_INFO is unnecessarily restrictive, from Michał Mirosław.

17) Fix triggerable race in ipv6 sysctl handling, from Francesco Ruggeri.

18) Statistics bug fixes in mlx4 from Eugenia Emantayev.

19) rds locking bug fix during info dumps, from your's truly.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (67 commits)
  rds: Make rds_sock_lock BH rather than IRQ safe.
  netprio_cgroup.h: dont include module.h from other includes
  net: flow_dissector.c missing include linux/export.h
  team: send only changed options/ports via netlink
  net/hyperv: fix possible memory leak in do_set_multicast()
  drivers/net: dsa/mv88e6xxx.c files need linux/module.h
  stmmac: added PCI identifiers
  llc: Fix race condition in llc_ui_recvmsg
  stmmac: fix phy naming inconsistency
  dsa: Add reporting of silicon revision for Marvell 88E6123/88E6161/88E6165 switches.
  tg3: fix ipv6 header length computation
  skge: add byte queue limit support
  mv643xx_eth: Add Rx Discard and Rx Overrun statistics
  bnx2x: fix compilation error with SOE in fw_dump
  bnx2x: handle CHIP_REVISION during init_one
  bnx2x: allow user to change ring size in ISCSI SD mode
  bnx2x: fix Big-Endianess in ethtool -t
  bnx2x: fixed ethtool statistics for MF modes
  bnx2x: credit-leakage fixup on vlan_mac_del_all
  macvlan: fix a possible use after free
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>mm: memcg: update the correct soft limit tree during migration</title>
<updated>2012-01-23T16:38:48+00:00</updated>
<author>
<name>Johannes Weiner</name>
<email>hannes@cmpxchg.org</email>
</author>
<published>2012-01-20T22:34:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=6568d4a9c9ff16d6c4f0b14dfea567806ce579e4'/>
<id>6568d4a9c9ff16d6c4f0b14dfea567806ce579e4</id>
<content type='text'>
end_migration() passes the old page instead of the new page to commit
the charge.  This page descriptor is not used for committing itself,
though, since we also pass the (correct) page_cgroup descriptor.  But
it's used to find the soft limit tree through the page's zone, so the
soft limit tree of the old page's zone is updated instead of that of the
new page's, which might get slightly out of date until the next charge
reaches the ratelimit point.

This glitch has been present since 5564e88 ("memcg: condense
page_cgroup-to-page lookup points").

This fixes a bug that I introduced in 2.6.38.  It's benign enough (to my
knowledge) that we probably don't want this for stable.

Reported-by: Hugh Dickins &lt;hughd@google.com&gt;
Signed-off-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Acked-by: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Acked-by: Michal Hocko &lt;mhocko@suse.cz&gt;
Acked-by: Kirill A. Shutemov &lt;kirill@shutemov.name&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
end_migration() passes the old page instead of the new page to commit
the charge.  This page descriptor is not used for committing itself,
though, since we also pass the (correct) page_cgroup descriptor.  But
it's used to find the soft limit tree through the page's zone, so the
soft limit tree of the old page's zone is updated instead of that of the
new page's, which might get slightly out of date until the next charge
reaches the ratelimit point.

This glitch has been present since 5564e88 ("memcg: condense
page_cgroup-to-page lookup points").

This fixes a bug that I introduced in 2.6.38.  It's benign enough (to my
knowledge) that we probably don't want this for stable.

Reported-by: Hugh Dickins &lt;hughd@google.com&gt;
Signed-off-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Acked-by: KAMEZAWA Hiroyuki &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Acked-by: Michal Hocko &lt;mhocko@suse.cz&gt;
Acked-by: Kirill A. Shutemov &lt;kirill@shutemov.name&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: fix socket memcg build with !CONFIG_NET</title>
<updated>2012-01-22T20:08:45+00:00</updated>
<author>
<name>Glauber Costa</name>
<email>glommer@parallels.com</email>
</author>
<published>2012-01-20T04:57:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=376be5ff8a6a36efadd131860cf26841f366d44c'/>
<id>376be5ff8a6a36efadd131860cf26841f366d44c</id>
<content type='text'>
There is still a build bug with the sock memcg code, that triggers
with !CONFIG_NET, that survived my series of randconfig builds.

Signed-off-by: Glauber Costa &lt;glommer@parallels.com&gt;
Reported-by: Randy Dunlap &lt;rdunlap@xenotime.net&gt;
CC: Hiroyouki Kamezawa &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There is still a build bug with the sock memcg code, that triggers
with !CONFIG_NET, that survived my series of randconfig builds.

Signed-off-by: Glauber Costa &lt;glommer@parallels.com&gt;
Reported-by: Randy Dunlap &lt;rdunlap@xenotime.net&gt;
CC: Hiroyouki Kamezawa &lt;kamezawa.hiroyu@jp.fujitsu.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
</feed>
