memory-controller patch fails to boot in qemu [mmotm]

memory-controller patch fails to boot in qemu [mmotm]

[Jiri Slaby]

Hi,

in mmotm-2009-07-30-05-01, the patch named
memory-controller-soft-limit-organize-cgroups-v9.patch
causes qemu fail to boot with tons of:
BUG: scheduling while atomic: async/2/480/0x10000002
Modules linked in:
Pid: 480, comm: async/2 Tainted: G       AW  2.6.31-rc4-mm1-bh #13
Call Trace:
 [<ffffffff81036b6c>] __schedule_bug+0x5c/0x70
 [<ffffffff8140491b>] thread_return+0x5c1/0x786
 [<ffffffff8103dd30>] __cond_resched+0x20/0x50
 [<ffffffff81404b9d>] _cond_resched+0x2d/0x40
 [<ffffffff81096694>] truncate_inode_pages_range+0x224/0x450
 [<ffffffff8106dfa1>] ? smp_call_function_many+0x1e1/0x210
 [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90
 [<ffffffff810e514b>] ? invalidate_bh_lru+0x7b/0x90
 [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90
 [<ffffffff810968d0>] truncate_inode_pages+0x10/0x20
 [<ffffffff810ea875>] kill_bdev+0x35/0x40
 [<ffffffff810eba18>] __blkdev_put+0xa8/0x190
 [<ffffffff810ebb0b>] blkdev_put+0xb/0x10
 [<ffffffff81116f62>] register_disk+0x172/0x180
 [<ffffffff8115bca5>] add_disk+0x85/0x150
 [<ffffffff812398cf>] sd_probe_async+0x12f/0x200
 [<ffffffff810616ca>] async_thread+0x10a/0x270
 [<ffffffff8103f7a0>] ? default_wake_function+0x0/0x10
 [<ffffffff810615c0>] ? async_thread+0x0/0x270
 [<ffffffff8105ac66>] kthread+0x96/0xa0
 [<ffffffff8100ceaa>] child_rip+0xa/0x20
 [<ffffffff8105abd0>] ? kthread+0x0/0xa0
 [<ffffffff8100cea0>] ? child_rip+0x0/0x20

Looks like an omitted unlock. I don't see anything suspicious in the
patch though.

The W taint flag is from:
WARNING: at /home/latest/bh/drivers/ata/libata-core.c:4980
ata_qc_complete+0x205/0x220()
Hardware name:
Modules linked in:
Pid: 226, comm: ata/0 Tainted: G       A   2.6.31-rc4-mm1-bh #13
Call Trace:
 [<ffffffff810441d8>] warn_slowpath_common+0x78/0xb0
 [<ffffffff8104421f>] warn_slowpath_null+0xf/0x20
 [<ffffffff8123e975>] ata_qc_complete+0x205/0x220
 [<ffffffff8124ac8b>] ata_do_link_abort+0xeb/0x110
 [<ffffffff8124acbb>] ata_port_abort+0xb/0x10
 [<ffffffff8124acea>] ata_port_freeze+0x2a/0x50
 [<ffffffff8124ea34>] ata_hsm_qc_complete+0x114/0x120
 [<ffffffff8124fbe2>] ata_sff_hsm_move+0x192/0x760
 [<ffffffff81250567>] ata_pio_task+0x37/0x130
 [<ffffffff81250530>] ? ata_pio_task+0x0/0x130
 [<ffffffff81056651>] worker_thread+0x151/0x250
 [<ffffffff8105afe0>] ? autoremove_wake_function+0x0/0x40
 [<ffffffff81056500>] ? worker_thread+0x0/0x250
 [<ffffffff8105ac66>] kthread+0x96/0xa0
 [<ffffffff8100ceaa>] child_rip+0xa/0x20
 [<ffffffff8105abd0>] ? kthread+0x0/0xa0
 [<ffffffff8100cea0>] ? child_rip+0x0/0x20
---[ end trace 4afa694ee13ac545 ]---
and is unrelated (it was always there).

Re: memory-controller patch fails to boot in qemu [mmotm]

[Jiri Slaby]

On 08/01/2009 04:07 PM, Jiri Slaby wrote:
> Looks like an omitted unlock. I don't see anything suspicious in the
> patch though.

CONFIG_TREE_RCU=y
btw

Re: memory-controller patch fails to boot in qemu [mmotm]

[Balbir Singh]

* Jiri Slaby <jirislaby@gmail.com> [2009-08-01 16:07:38]:

> Hi,
> 
> in mmotm-2009-07-30-05-01, the patch named
> memory-controller-soft-limit-organize-cgroups-v9.patch
> causes qemu fail to boot with tons of:
> BUG: scheduling while atomic: async/2/480/0x10000002
> Modules linked in:
> Pid: 480, comm: async/2 Tainted: G       AW  2.6.31-rc4-mm1-bh #13
> Call Trace:
>  [<ffffffff81036b6c>] __schedule_bug+0x5c/0x70
>  [<ffffffff8140491b>] thread_return+0x5c1/0x786
>  [<ffffffff8103dd30>] __cond_resched+0x20/0x50
>  [<ffffffff81404b9d>] _cond_resched+0x2d/0x40
>  [<ffffffff81096694>] truncate_inode_pages_range+0x224/0x450
>  [<ffffffff8106dfa1>] ? smp_call_function_many+0x1e1/0x210
>  [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90
>  [<ffffffff810e514b>] ? invalidate_bh_lru+0x7b/0x90
>  [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90
>  [<ffffffff810968d0>] truncate_inode_pages+0x10/0x20
>  [<ffffffff810ea875>] kill_bdev+0x35/0x40
>  [<ffffffff810eba18>] __blkdev_put+0xa8/0x190
>  [<ffffffff810ebb0b>] blkdev_put+0xb/0x10
>  [<ffffffff81116f62>] register_disk+0x172/0x180
>  [<ffffffff8115bca5>] add_disk+0x85/0x150
>  [<ffffffff812398cf>] sd_probe_async+0x12f/0x200
>  [<ffffffff810616ca>] async_thread+0x10a/0x270
>  [<ffffffff8103f7a0>] ? default_wake_function+0x0/0x10
>  [<ffffffff810615c0>] ? async_thread+0x0/0x270
>  [<ffffffff8105ac66>] kthread+0x96/0xa0
>  [<ffffffff8100ceaa>] child_rip+0xa/0x20
>  [<ffffffff8105abd0>] ? kthread+0x0/0xa0
>  [<ffffffff8100cea0>] ? child_rip+0x0/0x20
> 
> Looks like an omitted unlock. I don't see anything suspicious in the
> patch though.


Thanks for the report, did you bisect the mmotm series to identify the
root cause? What does your .config look like? I tried kvm with the
patches (mmotm 30th July) and qemu-kvm (30th-july) with a Fedora 11
guest image and the system booted just fine for me.

Could you share your command line as well?


-- 
	Balbir

Re: memory-controller patch fails to boot in qemu [mmotm]

[Hugh Dickins]

On Sun, 2 Aug 2009, Balbir Singh wrote:
> * Jiri Slaby <jirislaby@gmail.com> [2009-08-01 16:07:38]:
> > 
> > in mmotm-2009-07-30-05-01, the patch named
> > memory-controller-soft-limit-organize-cgroups-v9.patch
> > causes qemu fail to boot with tons of:
> > BUG: scheduling while atomic: async/2/480/0x10000002
> > Modules linked in:
> > Pid: 480, comm: async/2 Tainted: G       AW  2.6.31-rc4-mm1-bh #13
> > Call Trace:
> >  [<ffffffff81036b6c>] __schedule_bug+0x5c/0x70
> >  [<ffffffff8140491b>] thread_return+0x5c1/0x786
> >  [<ffffffff8103dd30>] __cond_resched+0x20/0x50
> >  [<ffffffff81404b9d>] _cond_resched+0x2d/0x40
> >  [<ffffffff81096694>] truncate_inode_pages_range+0x224/0x450
> >  [<ffffffff8106dfa1>] ? smp_call_function_many+0x1e1/0x210
> >  [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90
> >  [<ffffffff810e514b>] ? invalidate_bh_lru+0x7b/0x90
> >  [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90
> >  [<ffffffff810968d0>] truncate_inode_pages+0x10/0x20
> >  [<ffffffff810ea875>] kill_bdev+0x35/0x40
> >  [<ffffffff810eba18>] __blkdev_put+0xa8/0x190
> >  [<ffffffff810ebb0b>] blkdev_put+0xb/0x10
> >  [<ffffffff81116f62>] register_disk+0x172/0x180
> >  [<ffffffff8115bca5>] add_disk+0x85/0x150
> >  [<ffffffff812398cf>] sd_probe_async+0x12f/0x200
> >  [<ffffffff810616ca>] async_thread+0x10a/0x270
> >  [<ffffffff8103f7a0>] ? default_wake_function+0x0/0x10
> >  [<ffffffff810615c0>] ? async_thread+0x0/0x270
> >  [<ffffffff8105ac66>] kthread+0x96/0xa0
> >  [<ffffffff8100ceaa>] child_rip+0xa/0x20
> >  [<ffffffff8105abd0>] ? kthread+0x0/0xa0
> >  [<ffffffff8100cea0>] ? child_rip+0x0/0x20
> > 
> > Looks like an omitted unlock. I don't see anything suspicious in the
> > patch though.
> 
> 
> Thanks for the report, did you bisect the mmotm series to identify the
> root cause? What does your .config look like? I tried kvm with the
> patches (mmotm 30th July) and qemu-kvm (30th-july) with a Fedora 11
> guest image and the system booted just fine for me.
> 
> Could you share your command line as well?

I've just finished chasing something similar (without qemu),
and was about to post this:

[PATCH mmotm] memory controller: soft limit organize cgroups v9 fix

CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_PREEMPT=y mmotm fails to boot:
Kernel panic - not syncing: No init found; after lots of scheduling
while atomics, starting from when async_thread does sd_probe_async.

mem_cgroup_soft_limit_check() was doing an unbalanced get_cpu():
don't get_cpu if we won't need it, and put_cpu if we did get_cpu.

Hmm, this a weird function, passed an argument just to tell it to do
nothing.  Perhaps a placeholder for something more sensible to come?

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
---
Fix to memory-controller-soft-limit-organize-cgroups-v9.patch

 mm/memcontrol.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- mmotm/mm/memcontrol.c	2009-08-01 05:48:08.000000000 +0100
+++ linux/mm/memcontrol.c	2009-08-01 21:45:37.000000000 +0100
@@ -375,19 +375,21 @@ static bool mem_cgroup_soft_limit_check(
 					bool over_soft_limit)
 {
 	bool ret = false;
-	int cpu = get_cpu();
+	int cpu;
 	s64 val;
 	struct mem_cgroup_stat_cpu *cpustat;
 
 	if (!over_soft_limit)
 		return ret;
 
+	cpu = get_cpu();
 	cpustat = &mem->stat.cpustat[cpu];
 	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
 	if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
 		__mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
 		ret = true;
 	}
+	put_cpu();
 	return ret;
 }
 

Re: memory-controller patch fails to boot in qemu [mmotm]

[Balbir Singh]

* Hugh Dickins <hugh.dickins@tiscali.co.uk> [2009-08-01 23:09:09]:

> On Sun, 2 Aug 2009, Balbir Singh wrote:
> > * Jiri Slaby <jirislaby@gmail.com> [2009-08-01 16:07:38]:
> > > 
> > > in mmotm-2009-07-30-05-01, the patch named
> > > memory-controller-soft-limit-organize-cgroups-v9.patch
> > > causes qemu fail to boot with tons of:
> > > BUG: scheduling while atomic: async/2/480/0x10000002
> > > Modules linked in:
> > > Pid: 480, comm: async/2 Tainted: G       AW  2.6.31-rc4-mm1-bh #13
> > > Call Trace:
> > >  [<ffffffff81036b6c>] __schedule_bug+0x5c/0x70
> > >  [<ffffffff8140491b>] thread_return+0x5c1/0x786
> > >  [<ffffffff8103dd30>] __cond_resched+0x20/0x50
> > >  [<ffffffff81404b9d>] _cond_resched+0x2d/0x40
> > >  [<ffffffff81096694>] truncate_inode_pages_range+0x224/0x450
> > >  [<ffffffff8106dfa1>] ? smp_call_function_many+0x1e1/0x210
> > >  [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90
> > >  [<ffffffff810e514b>] ? invalidate_bh_lru+0x7b/0x90
> > >  [<ffffffff810e50d0>] ? invalidate_bh_lru+0x0/0x90
> > >  [<ffffffff810968d0>] truncate_inode_pages+0x10/0x20
> > >  [<ffffffff810ea875>] kill_bdev+0x35/0x40
> > >  [<ffffffff810eba18>] __blkdev_put+0xa8/0x190
> > >  [<ffffffff810ebb0b>] blkdev_put+0xb/0x10
> > >  [<ffffffff81116f62>] register_disk+0x172/0x180
> > >  [<ffffffff8115bca5>] add_disk+0x85/0x150
> > >  [<ffffffff812398cf>] sd_probe_async+0x12f/0x200
> > >  [<ffffffff810616ca>] async_thread+0x10a/0x270
> > >  [<ffffffff8103f7a0>] ? default_wake_function+0x0/0x10
> > >  [<ffffffff810615c0>] ? async_thread+0x0/0x270
> > >  [<ffffffff8105ac66>] kthread+0x96/0xa0
> > >  [<ffffffff8100ceaa>] child_rip+0xa/0x20
> > >  [<ffffffff8105abd0>] ? kthread+0x0/0xa0
> > >  [<ffffffff8100cea0>] ? child_rip+0x0/0x20
> > > 
> > > Looks like an omitted unlock. I don't see anything suspicious in the
> > > patch though.
> > 
> > 
> > Thanks for the report, did you bisect the mmotm series to identify the
> > root cause? What does your .config look like? I tried kvm with the
> > patches (mmotm 30th July) and qemu-kvm (30th-july) with a Fedora 11
> > guest image and the system booted just fine for me.
> > 
> > Could you share your command line as well?
> 
> I've just finished chasing something similar (without qemu),
> and was about to post this:
> 
> [PATCH mmotm] memory controller: soft limit organize cgroups v9 fix
> 
> CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_PREEMPT=y mmotm fails to boot:
> Kernel panic - not syncing: No init found; after lots of scheduling
> while atomics, starting from when async_thread does sd_probe_async.
> 
> mem_cgroup_soft_limit_check() was doing an unbalanced get_cpu():
> don't get_cpu if we won't need it, and put_cpu if we did get_cpu.
> 
> Hmm, this a weird function, passed an argument just to tell it to do
> nothing.  Perhaps a placeholder for something more sensible to come?

The argument is passed a result of a function, It no-ops quite
frequently for the root cgroup.

> 
> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
> ---
> Fix to memory-controller-soft-limit-organize-cgroups-v9.patch
> 
>  mm/memcontrol.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> --- mmotm/mm/memcontrol.c	2009-08-01 05:48:08.000000000 +0100
> +++ linux/mm/memcontrol.c	2009-08-01 21:45:37.000000000 +0100
> @@ -375,19 +375,21 @@ static bool mem_cgroup_soft_limit_check(
>  					bool over_soft_limit)
>  {
>  	bool ret = false;
> -	int cpu = get_cpu();
> +	int cpu;
>  	s64 val;
>  	struct mem_cgroup_stat_cpu *cpustat;
> 
>  	if (!over_soft_limit)
>  		return ret;
> 
> +	cpu = get_cpu();
>  	cpustat = &mem->stat.cpustat[cpu];
>  	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
>  	if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
>  		__mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
>  		ret = true;
>  	}
> +	put_cpu();
>  	return ret;
>  }
> 

Thanks, my bad, I should have spotted the missing put_cpu(). I'll test
this with CONFIG_PREEMPT, CONFIG_PREEMPT_DEBUG and report back. The
patch obviously looks correct, but I'll test it as well.


-- 
	Balbir

Re: memory-controller patch fails to boot in qemu [mmotm]

[Hugh Dickins]

On Sun, 2 Aug 2009, Balbir Singh wrote:
> * Hugh Dickins <hugh.dickins@tiscali.co.uk> [2009-08-01 23:09:09]:
> > 
> > Hmm, this a weird function, passed an argument just to tell it to do
> > nothing.  Perhaps a placeholder for something more sensible to come?
> 
> The argument is passed a result of a function, It no-ops quite
> frequently for the root cgroup.

The more often it no-ops, the sillier it is to be called in
the first place: here's an updated patch which fixes that too.


[PATCH mmotm] memory controller: soft limit organize cgroups v9 fix

CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_PREEMPT=y mmotm fails to boot:
Kernel panic - not syncing: No init found; after lots of scheduling
while atomics, starting from when async_thread does sd_probe_async.

mem_cgroup_soft_limit_check() was doing an unbalanced get_cpu():
don't get_cpu if we won't need it, and put_cpu if we did get_cpu.

And fix the silliness of passing it an "over_soft_limit" argument
that just tells it to return false when false.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
---
Fix to memory-controller-soft-limit-organize-cgroups-v9.patch

 mm/memcontrol.c |   14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

--- mmotm/mm/memcontrol.c	2009-08-01 05:48:08.000000000 +0100
+++ linux/mm/memcontrol.c	2009-08-02 16:56:02.000000000 +0100
@@ -371,23 +371,21 @@ mem_cgroup_remove_exceeded(struct mem_cg
 	spin_unlock(&mctz->lock);
 }
 
-static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem,
-					bool over_soft_limit)
+static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem)
 {
 	bool ret = false;
-	int cpu = get_cpu();
+	int cpu;
 	s64 val;
 	struct mem_cgroup_stat_cpu *cpustat;
 
-	if (!over_soft_limit)
-		return ret;
-
+	cpu = get_cpu();
 	cpustat = &mem->stat.cpustat[cpu];
 	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
 	if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
 		__mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
 		ret = true;
 	}
+	put_cpu();
 	return ret;
 }
 
@@ -1342,7 +1340,7 @@ static int __mem_cgroup_try_charge(struc
 	if (soft_fail_res) {
 		mem_over_soft_limit =
 			mem_cgroup_from_res_counter(soft_fail_res, res);
-		if (mem_cgroup_soft_limit_check(mem_over_soft_limit, true))
+		if (mem_cgroup_soft_limit_check(mem_over_soft_limit))
 			mem_cgroup_update_tree(mem_over_soft_limit, page);
 	}
 	return 0;
@@ -1873,7 +1871,7 @@ __mem_cgroup_uncharge_common(struct page
 	mz = page_cgroup_zoneinfo(pc);
 	unlock_page_cgroup(pc);
 
-	if (mem_cgroup_soft_limit_check(mem, soft_limit_excess))
+	if (soft_limit_excess && mem_cgroup_soft_limit_check(mem))
 		mem_cgroup_update_tree(mem, page);
 	/* at swapout, this memcg will be accessed to record to swap */
 	if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)

Re: memory-controller patch fails to boot in qemu [mmotm]

[KAMEZAWA Hiroyuki]

Hugh Dickins wrote:
> On Sun, 2 Aug 2009, Balbir Singh wrote:
>> * Hugh Dickins <hugh.dickins@tiscali.co.uk> [2009-08-01 23:09:09]:
>> >
>> > Hmm, this a weird function, passed an argument just to tell it to do
>> > nothing.  Perhaps a placeholder for something more sensible to come?
>>
>> The argument is passed a result of a function, It no-ops quite
>> frequently for the root cgroup.
>
> The more often it no-ops, the sillier it is to be called in
> the first place: here's an updated patch which fixes that too.
>
>
> [PATCH mmotm] memory controller: soft limit organize cgroups v9 fix
>
> CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_PREEMPT=y mmotm fails to boot:
> Kernel panic - not syncing: No init found; after lots of scheduling
> while atomics, starting from when async_thread does sd_probe_async.
>
> mem_cgroup_soft_limit_check() was doing an unbalanced get_cpu():
> don't get_cpu if we won't need it, and put_cpu if we did get_cpu.
>
> And fix the silliness of passing it an "over_soft_limit" argument
> that just tells it to return false when false.
>
> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>

nice fix, thank you very much.

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

> ---
> Fix to memory-controller-soft-limit-organize-cgroups-v9.patch
>
>  mm/memcontrol.c |   14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
>
> --- mmotm/mm/memcontrol.c	2009-08-01 05:48:08.000000000 +0100
> +++ linux/mm/memcontrol.c	2009-08-02 16:56:02.000000000 +0100
> @@ -371,23 +371,21 @@ mem_cgroup_remove_exceeded(struct mem_cg
>  	spin_unlock(&mctz->lock);
>  }
>
> -static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem,
> -					bool over_soft_limit)
> +static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem)
>  {
>  	bool ret = false;
> -	int cpu = get_cpu();
> +	int cpu;
>  	s64 val;
>  	struct mem_cgroup_stat_cpu *cpustat;
>
> -	if (!over_soft_limit)
> -		return ret;
> -
> +	cpu = get_cpu();
>  	cpustat = &mem->stat.cpustat[cpu];
>  	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
>  	if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
>  		__mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
>  		ret = true;
>  	}
> +	put_cpu();
>  	return ret;
>  }
>
> @@ -1342,7 +1340,7 @@ static int __mem_cgroup_try_charge(struc
>  	if (soft_fail_res) {
>  		mem_over_soft_limit =
>  			mem_cgroup_from_res_counter(soft_fail_res, res);
> -		if (mem_cgroup_soft_limit_check(mem_over_soft_limit, true))
> +		if (mem_cgroup_soft_limit_check(mem_over_soft_limit))
>  			mem_cgroup_update_tree(mem_over_soft_limit, page);
>  	}
>  	return 0;
> @@ -1873,7 +1871,7 @@ __mem_cgroup_uncharge_common(struct page
>  	mz = page_cgroup_zoneinfo(pc);
>  	unlock_page_cgroup(pc);
>
> -	if (mem_cgroup_soft_limit_check(mem, soft_limit_excess))
> +	if (soft_limit_excess && mem_cgroup_soft_limit_check(mem))
>  		mem_cgroup_update_tree(mem, page);
>  	/* at swapout, this memcg will be accessed to record to swap */
>  	if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
>

Re: memory-controller patch fails to boot in qemu [mmotm]

[Balbir Singh]

* Hugh Dickins <hugh.dickins@tiscali.co.uk> [2009-08-02 17:12:53]:

> On Sun, 2 Aug 2009, Balbir Singh wrote:
> > * Hugh Dickins <hugh.dickins@tiscali.co.uk> [2009-08-01 23:09:09]:
> > > 
> > > Hmm, this a weird function, passed an argument just to tell it to do
> > > nothing.  Perhaps a placeholder for something more sensible to come?
> > 
> > The argument is passed a result of a function, It no-ops quite
> > frequently for the root cgroup.
> 
> The more often it no-ops, the sillier it is to be called in
> the first place: here's an updated patch which fixes that too.
> 
> 
> [PATCH mmotm] memory controller: soft limit organize cgroups v9 fix
> 
> CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_PREEMPT=y mmotm fails to boot:
> Kernel panic - not syncing: No init found; after lots of scheduling
> while atomics, starting from when async_thread does sd_probe_async.
> 
> mem_cgroup_soft_limit_check() was doing an unbalanced get_cpu():
> don't get_cpu if we won't need it, and put_cpu if we did get_cpu.
> 
> And fix the silliness of passing it an "over_soft_limit" argument
> that just tells it to return false when false.
> 
> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>

Fair enough (I guess my intention of keeping if blocks outside for
each call site, does not pay sufficiently enough), Thanks for the cleanup


Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com>
 

-- 
	Balbir

Re: memory-controller patch fails to boot in qemu [mmotm]

[Balbir Singh]

* Hugh Dickins <hugh.dickins@tiscali.co.uk> [2009-08-01 23:09:09]:

> I've just finished chasing something similar (without qemu),
> and was about to post this:
> 
> [PATCH mmotm] memory controller: soft limit organize cgroups v9 fix
> 
> CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_PREEMPT=y mmotm fails to boot:
> Kernel panic - not syncing: No init found; after lots of scheduling
> while atomics, starting from when async_thread does sd_probe_async.
> 
> mem_cgroup_soft_limit_check() was doing an unbalanced get_cpu():
> don't get_cpu if we won't need it, and put_cpu if we did get_cpu.
> 
> Hmm, this a weird function, passed an argument just to tell it to do
> nothing.  Perhaps a placeholder for something more sensible to come?
> 
> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
> ---
> Fix to memory-controller-soft-limit-organize-cgroups-v9.patch
> 
>  mm/memcontrol.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> --- mmotm/mm/memcontrol.c	2009-08-01 05:48:08.000000000 +0100
> +++ linux/mm/memcontrol.c	2009-08-01 21:45:37.000000000 +0100
> @@ -375,19 +375,21 @@ static bool mem_cgroup_soft_limit_check(
>  					bool over_soft_limit)
>  {
>  	bool ret = false;
> -	int cpu = get_cpu();
> +	int cpu;
>  	s64 val;
>  	struct mem_cgroup_stat_cpu *cpustat;
> 
>  	if (!over_soft_limit)
>  		return ret;
> 
> +	cpu = get_cpu();
>  	cpustat = &mem->stat.cpustat[cpu];
>  	val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
>  	if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
>  		__mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
>  		ret = true;
>  	}
> +	put_cpu();
>  	return ret;
>  }
>

I can confirm that this fixes the problem with CONFIG_PREEMPT enabled.

Tested-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
 

-- 
	Balbir