* kernel warning: tried to kill an mm-less task!
@ 2008-04-14 7:09 ` Li Zefan
0 siblings, 0 replies; 18+ messages in thread
From: Li Zefan @ 2008-04-14 7:09 UTC (permalink / raw
To: linux-mm@kvack.org
Cc: LKML, Andrew Morton, Balbir Singh, KAMEZAWA Hiroyuki,
Pavel Emelianov
When I ran the same test program I described in a previous patch,
I got the following warning:
WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
Modules linked in:
Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
[<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
[<ffffffff80244e16>] printk+0x5e/0x7b
[<ffffffff8022b096>] page_count+0x25/0x49
[<ffffffff8022b2cd>] show_mem+0x125/0x15a
[<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
[<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
[<ffffffff8028f72c>] select_bad_process+0xb0/0x122
[<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
[<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
[<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
[<ffffffff8029ebca>] follow_page+0x191/0x27d
[<ffffffff80234155>] need_resched+0x31/0x4f
[<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
[<ffffffff802a1f64>] make_pages_present+0x9e/0xca
[<ffffffff802a51fc>] mmap_region+0x38c/0x452
[<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
[<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
[<ffffffff805037ee>] _cond_resched+0x1c/0x5f
[<ffffffff80211715>] sys_mmap+0xf5/0x138
[<ffffffff8020c6d2>] tracesys+0xd5/0xda
---[ end trace fe959fb2f0473e7c ]---
tried to kill an mm-less task!
This showed up several times in some seconds, but then didn't appear
any more. And it's reproducable in a x86_64 box, but doesn't happen
in a x86_32 one.
And this happens both with and without the oops fixing.
Regards,
Li Zefan
^ permalink raw reply [flat|nested] 18+ messages in thread
* kernel warning: tried to kill an mm-less task!
@ 2008-04-14 7:09 ` Li Zefan
0 siblings, 0 replies; 18+ messages in thread
From: Li Zefan @ 2008-04-14 7:09 UTC (permalink / raw
To: linux-mm@kvack.org
Cc: LKML, Andrew Morton, Balbir Singh, KAMEZAWA Hiroyuki,
Pavel Emelianov
When I ran the same test program I described in a previous patch,
I got the following warning:
WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
Modules linked in:
Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
[<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
[<ffffffff80244e16>] printk+0x5e/0x7b
[<ffffffff8022b096>] page_count+0x25/0x49
[<ffffffff8022b2cd>] show_mem+0x125/0x15a
[<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
[<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
[<ffffffff8028f72c>] select_bad_process+0xb0/0x122
[<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
[<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
[<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
[<ffffffff8029ebca>] follow_page+0x191/0x27d
[<ffffffff80234155>] need_resched+0x31/0x4f
[<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
[<ffffffff802a1f64>] make_pages_present+0x9e/0xca
[<ffffffff802a51fc>] mmap_region+0x38c/0x452
[<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
[<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
[<ffffffff805037ee>] _cond_resched+0x1c/0x5f
[<ffffffff80211715>] sys_mmap+0xf5/0x138
[<ffffffff8020c6d2>] tracesys+0xd5/0xda
---[ end trace fe959fb2f0473e7c ]---
tried to kill an mm-less task!
This showed up several times in some seconds, but then didn't appear
any more. And it's reproducable in a x86_64 box, but doesn't happen
in a x86_32 one.
And this happens both with and without the oops fixing.
Regards,
Li Zefan
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
2008-04-14 7:09 ` Li Zefan
@ 2008-04-14 7:46 ` KAMEZAWA Hiroyuki
-1 siblings, 0 replies; 18+ messages in thread
From: KAMEZAWA Hiroyuki @ 2008-04-14 7:46 UTC (permalink / raw
To: Li Zefan
Cc: linux-mm@kvack.org, LKML, Andrew Morton, Balbir Singh,
Pavel Emelianov
On Mon, 14 Apr 2008 15:09:01 +0800
Li Zefan <lizf@cn.fujitsu.com> wrote:
> When I ran the same test program I described in a previous patch,
> I got the following warning:
>
> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
> Modules linked in:
>
> Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
> [<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
> [<ffffffff80244e16>] printk+0x5e/0x7b
> [<ffffffff8022b096>] page_count+0x25/0x49
> [<ffffffff8022b2cd>] show_mem+0x125/0x15a
> [<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
> [<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
> [<ffffffff8028f72c>] select_bad_process+0xb0/0x122
> [<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
> [<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
> [<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
> [<ffffffff8029ebca>] follow_page+0x191/0x27d
> [<ffffffff80234155>] need_resched+0x31/0x4f
> [<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
> [<ffffffff802a1f64>] make_pages_present+0x9e/0xca
> [<ffffffff802a51fc>] mmap_region+0x38c/0x452
> [<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
> [<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
> [<ffffffff805037ee>] _cond_resched+0x1c/0x5f
> [<ffffffff80211715>] sys_mmap+0xf5/0x138
> [<ffffffff8020c6d2>] tracesys+0xd5/0xda
> ---[ end trace fe959fb2f0473e7c ]---
> tried to kill an mm-less task!
>
> This showed up several times in some seconds, but then didn't appear
> any more. And it's reproducable in a x86_64 box, but doesn't happen
> in a x86_32 one.
>
> And this happens both with and without the oops fixing.
>
It seems this warning itself is not necessary....
-Kame
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
@ 2008-04-14 7:46 ` KAMEZAWA Hiroyuki
0 siblings, 0 replies; 18+ messages in thread
From: KAMEZAWA Hiroyuki @ 2008-04-14 7:46 UTC (permalink / raw
To: Li Zefan
Cc: linux-mm@kvack.org, LKML, Andrew Morton, Balbir Singh,
Pavel Emelianov
On Mon, 14 Apr 2008 15:09:01 +0800
Li Zefan <lizf@cn.fujitsu.com> wrote:
> When I ran the same test program I described in a previous patch,
> I got the following warning:
>
> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
> Modules linked in:
>
> Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
> [<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
> [<ffffffff80244e16>] printk+0x5e/0x7b
> [<ffffffff8022b096>] page_count+0x25/0x49
> [<ffffffff8022b2cd>] show_mem+0x125/0x15a
> [<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
> [<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
> [<ffffffff8028f72c>] select_bad_process+0xb0/0x122
> [<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
> [<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
> [<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
> [<ffffffff8029ebca>] follow_page+0x191/0x27d
> [<ffffffff80234155>] need_resched+0x31/0x4f
> [<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
> [<ffffffff802a1f64>] make_pages_present+0x9e/0xca
> [<ffffffff802a51fc>] mmap_region+0x38c/0x452
> [<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
> [<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
> [<ffffffff805037ee>] _cond_resched+0x1c/0x5f
> [<ffffffff80211715>] sys_mmap+0xf5/0x138
> [<ffffffff8020c6d2>] tracesys+0xd5/0xda
> ---[ end trace fe959fb2f0473e7c ]---
> tried to kill an mm-less task!
>
> This showed up several times in some seconds, but then didn't appear
> any more. And it's reproducable in a x86_64 box, but doesn't happen
> in a x86_32 one.
>
> And this happens both with and without the oops fixing.
>
It seems this warning itself is not necessary....
-Kame
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
2008-04-14 7:09 ` Li Zefan
@ 2008-04-14 8:01 ` Balbir Singh
-1 siblings, 0 replies; 18+ messages in thread
From: Balbir Singh @ 2008-04-14 8:01 UTC (permalink / raw
To: Li Zefan
Cc: linux-mm@kvack.org, LKML, Andrew Morton, KAMEZAWA Hiroyuki,
Pavel Emelianov
Li Zefan wrote:
> When I ran the same test program I described in a previous patch,
> I got the following warning:
>
> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
> Modules linked in:
>
> Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
> [<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
> [<ffffffff80244e16>] printk+0x5e/0x7b
> [<ffffffff8022b096>] page_count+0x25/0x49
> [<ffffffff8022b2cd>] show_mem+0x125/0x15a
> [<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
> [<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
> [<ffffffff8028f72c>] select_bad_process+0xb0/0x122
> [<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
> [<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
> [<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
> [<ffffffff8029ebca>] follow_page+0x191/0x27d
> [<ffffffff80234155>] need_resched+0x31/0x4f
> [<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
> [<ffffffff802a1f64>] make_pages_present+0x9e/0xca
> [<ffffffff802a51fc>] mmap_region+0x38c/0x452
> [<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
> [<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
> [<ffffffff805037ee>] _cond_resched+0x1c/0x5f
> [<ffffffff80211715>] sys_mmap+0xf5/0x138
> [<ffffffff8020c6d2>] tracesys+0xd5/0xda
> ---[ end trace fe959fb2f0473e7c ]---
> tried to kill an mm-less task!
>
> This showed up several times in some seconds, but then didn't appear
> any more. And it's reproducable in a x86_64 box, but doesn't happen
> in a x86_32 one.
>
> And this happens both with and without the oops fixing.
>
Could we get some more details on which task was chosen to be killed? It will be
nice to see the task flags as well to see if PF_EXITING is set.
oom_kill_task() has a big WARNING in the comment
/* WARNING: mm may not be dereferenced since we did not obtain its
* value from get_task_mm(p). This is OK since all we need to do is
* compare mm to q->mm below.
I want to see the flags to see if
PF_BORROWED_MM or PF_EXIT* is set.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
@ 2008-04-14 8:01 ` Balbir Singh
0 siblings, 0 replies; 18+ messages in thread
From: Balbir Singh @ 2008-04-14 8:01 UTC (permalink / raw
To: Li Zefan
Cc: linux-mm@kvack.org, LKML, Andrew Morton, KAMEZAWA Hiroyuki,
Pavel Emelianov
Li Zefan wrote:
> When I ran the same test program I described in a previous patch,
> I got the following warning:
>
> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
> Modules linked in:
>
> Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
> [<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
> [<ffffffff80244e16>] printk+0x5e/0x7b
> [<ffffffff8022b096>] page_count+0x25/0x49
> [<ffffffff8022b2cd>] show_mem+0x125/0x15a
> [<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
> [<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
> [<ffffffff8028f72c>] select_bad_process+0xb0/0x122
> [<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
> [<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
> [<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
> [<ffffffff8029ebca>] follow_page+0x191/0x27d
> [<ffffffff80234155>] need_resched+0x31/0x4f
> [<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
> [<ffffffff802a1f64>] make_pages_present+0x9e/0xca
> [<ffffffff802a51fc>] mmap_region+0x38c/0x452
> [<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
> [<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
> [<ffffffff805037ee>] _cond_resched+0x1c/0x5f
> [<ffffffff80211715>] sys_mmap+0xf5/0x138
> [<ffffffff8020c6d2>] tracesys+0xd5/0xda
> ---[ end trace fe959fb2f0473e7c ]---
> tried to kill an mm-less task!
>
> This showed up several times in some seconds, but then didn't appear
> any more. And it's reproducable in a x86_64 box, but doesn't happen
> in a x86_32 one.
>
> And this happens both with and without the oops fixing.
>
Could we get some more details on which task was chosen to be killed? It will be
nice to see the task flags as well to see if PF_EXITING is set.
oom_kill_task() has a big WARNING in the comment
/* WARNING: mm may not be dereferenced since we did not obtain its
* value from get_task_mm(p). This is OK since all we need to do is
* compare mm to q->mm below.
I want to see the flags to see if
PF_BORROWED_MM or PF_EXIT* is set.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
2008-04-14 8:01 ` Balbir Singh
@ 2008-04-14 8:06 ` Li Zefan
-1 siblings, 0 replies; 18+ messages in thread
From: Li Zefan @ 2008-04-14 8:06 UTC (permalink / raw
To: balbir
Cc: linux-mm@kvack.org, LKML, Andrew Morton, KAMEZAWA Hiroyuki,
Pavel Emelianov
Balbir Singh wrote:
> Li Zefan wrote:
>> When I ran the same test program I described in a previous patch,
>> I got the following warning:
>>
>> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
>> Modules linked in:
>>
>> Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
>> [<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
>> [<ffffffff80244e16>] printk+0x5e/0x7b
>> [<ffffffff8022b096>] page_count+0x25/0x49
>> [<ffffffff8022b2cd>] show_mem+0x125/0x15a
>> [<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
>> [<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
>> [<ffffffff8028f72c>] select_bad_process+0xb0/0x122
>> [<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
>> [<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
>> [<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
>> [<ffffffff8029ebca>] follow_page+0x191/0x27d
>> [<ffffffff80234155>] need_resched+0x31/0x4f
>> [<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
>> [<ffffffff802a1f64>] make_pages_present+0x9e/0xca
>> [<ffffffff802a51fc>] mmap_region+0x38c/0x452
>> [<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
>> [<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
>> [<ffffffff805037ee>] _cond_resched+0x1c/0x5f
>> [<ffffffff80211715>] sys_mmap+0xf5/0x138
>> [<ffffffff8020c6d2>] tracesys+0xd5/0xda
>> ---[ end trace fe959fb2f0473e7c ]---
>> tried to kill an mm-less task!
>>
>> This showed up several times in some seconds, but then didn't appear
>> any more. And it's reproducable in a x86_64 box, but doesn't happen
>> in a x86_32 one.
>>
>> And this happens both with and without the oops fixing.
>>
>
> Could we get some more details on which task was chosen to be killed? It will be
> nice to see the task flags as well to see if PF_EXITING is set.
>
> oom_kill_task() has a big WARNING in the comment
>
> /* WARNING: mm may not be dereferenced since we did not obtain its
> * value from get_task_mm(p). This is OK since all we need to do is
> * compare mm to q->mm below.
>
>
> I want to see the flags to see if
>
> PF_BORROWED_MM or PF_EXIT* is set.
>
>
OK, I'll try.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
@ 2008-04-14 8:06 ` Li Zefan
0 siblings, 0 replies; 18+ messages in thread
From: Li Zefan @ 2008-04-14 8:06 UTC (permalink / raw
To: balbir
Cc: linux-mm@kvack.org, LKML, Andrew Morton, KAMEZAWA Hiroyuki,
Pavel Emelianov
Balbir Singh wrote:
> Li Zefan wrote:
>> When I ran the same test program I described in a previous patch,
>> I got the following warning:
>>
>> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
>> Modules linked in:
>>
>> Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
>> [<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
>> [<ffffffff80244e16>] printk+0x5e/0x7b
>> [<ffffffff8022b096>] page_count+0x25/0x49
>> [<ffffffff8022b2cd>] show_mem+0x125/0x15a
>> [<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
>> [<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
>> [<ffffffff8028f72c>] select_bad_process+0xb0/0x122
>> [<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
>> [<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
>> [<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
>> [<ffffffff8029ebca>] follow_page+0x191/0x27d
>> [<ffffffff80234155>] need_resched+0x31/0x4f
>> [<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
>> [<ffffffff802a1f64>] make_pages_present+0x9e/0xca
>> [<ffffffff802a51fc>] mmap_region+0x38c/0x452
>> [<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
>> [<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
>> [<ffffffff805037ee>] _cond_resched+0x1c/0x5f
>> [<ffffffff80211715>] sys_mmap+0xf5/0x138
>> [<ffffffff8020c6d2>] tracesys+0xd5/0xda
>> ---[ end trace fe959fb2f0473e7c ]---
>> tried to kill an mm-less task!
>>
>> This showed up several times in some seconds, but then didn't appear
>> any more. And it's reproducable in a x86_64 box, but doesn't happen
>> in a x86_32 one.
>>
>> And this happens both with and without the oops fixing.
>>
>
> Could we get some more details on which task was chosen to be killed? It will be
> nice to see the task flags as well to see if PF_EXITING is set.
>
> oom_kill_task() has a big WARNING in the comment
>
> /* WARNING: mm may not be dereferenced since we did not obtain its
> * value from get_task_mm(p). This is OK since all we need to do is
> * compare mm to q->mm below.
>
>
> I want to see the flags to see if
>
> PF_BORROWED_MM or PF_EXIT* is set.
>
>
OK, I'll try.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
2008-04-14 8:06 ` Li Zefan
@ 2008-04-15 3:47 ` Li Zefan
-1 siblings, 0 replies; 18+ messages in thread
From: Li Zefan @ 2008-04-15 3:47 UTC (permalink / raw
To: balbir
Cc: linux-mm@kvack.org, LKML, Andrew Morton, KAMEZAWA Hiroyuki,
Pavel Emelianov, Oleg Nesterov
CC: Oleg Nesterov <oleg@tv-sign.ru>
Li Zefan wrote:
> Balbir Singh wrote:
>> Li Zefan wrote:
>>> When I ran the same test program I described in a previous patch,
>>> I got the following warning:
>>>
>>> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
>>> Modules linked in:
>>>
>>> Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
>>> [<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
>>> [<ffffffff80244e16>] printk+0x5e/0x7b
>>> [<ffffffff8022b096>] page_count+0x25/0x49
>>> [<ffffffff8022b2cd>] show_mem+0x125/0x15a
>>> [<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
>>> [<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
>>> [<ffffffff8028f72c>] select_bad_process+0xb0/0x122
>>> [<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
>>> [<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
>>> [<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
>>> [<ffffffff8029ebca>] follow_page+0x191/0x27d
>>> [<ffffffff80234155>] need_resched+0x31/0x4f
>>> [<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
>>> [<ffffffff802a1f64>] make_pages_present+0x9e/0xca
>>> [<ffffffff802a51fc>] mmap_region+0x38c/0x452
>>> [<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
>>> [<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
>>> [<ffffffff805037ee>] _cond_resched+0x1c/0x5f
>>> [<ffffffff80211715>] sys_mmap+0xf5/0x138
>>> [<ffffffff8020c6d2>] tracesys+0xd5/0xda
>>> ---[ end trace fe959fb2f0473e7c ]---
>>> tried to kill an mm-less task!
>>>
>>> This showed up several times in some seconds, but then didn't appear
>>> any more. And it's reproducable in a x86_64 box, but doesn't happen
>>> in a x86_32 one.
>>>
>>> And this happens both with and without the oops fixing.
>>>
>> Could we get some more details on which task was chosen to be killed? It will be
>> nice to see the task flags as well to see if PF_EXITING is set.
>>
>> oom_kill_task() has a big WARNING in the comment
>>
>> /* WARNING: mm may not be dereferenced since we did not obtain its
>> * value from get_task_mm(p). This is OK since all we need to do is
>> * compare mm to q->mm below.
>>
>>
>> I want to see the flags to see if
>>
>> PF_BORROWED_MM or PF_EXIT* is set.
>>
>>
>
> OK, I'll try.
>
> --
I Added 2 printk()s:
static void __oom_kill_task(struct task_struct *p, int verbose)
{
+ printk(KERN_WARNING "pid = %d, flags = %x\n", p->pid, p->flags);
+
if (is_global_init(p)) {
WARN_ON(1);
printk(KERN_WARNING "tried to kill init!\n");
@@ -319,6 +320,7 @@ static void __oom_kill_task(struct task_struct *p, int verbo
if (!p->mm) {
WARN_ON(1);
+ printk(KERN_WARNING "pid = %d, flags = %x\n", p->pid, p->flags);
printk(KERN_WARNING "tried to kill an mm-less task!\n");
return;
}
got this:
pid = 3817, flags = 400140
------------[ cut here ]------------
WARNING: at mm/oom_kill.c:322 __oom_kill_task+0x74/0xf1()
...
---[ end trace bb92f2fd8fe6c7c5 ]---
pid = 3817, flags = 400144
tried to kill an mm-less task!
So PF_EXITING may be set during the call of oom_kill_task(), and I notice
the comment in oom_kill_task():
* Furthermore, even if mm contains a non-NULL value, p->mm may
* change to NULL at any time since we do not hold task_lock(p).
* However, this is of no concern to us.
Is this warning just harmless so that we can just ignore it ?
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
@ 2008-04-15 3:47 ` Li Zefan
0 siblings, 0 replies; 18+ messages in thread
From: Li Zefan @ 2008-04-15 3:47 UTC (permalink / raw
To: balbir
Cc: linux-mm@kvack.org, LKML, Andrew Morton, KAMEZAWA Hiroyuki,
Pavel Emelianov, Oleg Nesterov
Li Zefan wrote:
> Balbir Singh wrote:
>> Li Zefan wrote:
>>> When I ran the same test program I described in a previous patch,
>>> I got the following warning:
>>>
>>> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
>>> Modules linked in:
>>>
>>> Pid: 3856, comm: a.out Not tainted 2.6.25-rc8-mm2 #37
>>> [<ffffffff80243941>] warn_on_slowpath+0x64/0xa2
>>> [<ffffffff80244e16>] printk+0x5e/0x7b
>>> [<ffffffff8022b096>] page_count+0x25/0x49
>>> [<ffffffff8022b2cd>] show_mem+0x125/0x15a
>>> [<ffffffff8028f00f>] __oom_kill_task+0x6d/0x101
>>> [<ffffffff8028f319>] oom_kill_process+0x16c/0x22e
>>> [<ffffffff8028f72c>] select_bad_process+0xb0/0x122
>>> [<ffffffff8028f8d3>] mem_cgroup_out_of_memory+0x65/0x8a
>>> [<ffffffff802bee84>] mem_cgroup_charge_common+0xf8/0x215
>>> [<ffffffff802a14ac>] handle_mm_fault+0x216/0x6c8
>>> [<ffffffff8029ebca>] follow_page+0x191/0x27d
>>> [<ffffffff80234155>] need_resched+0x31/0x4f
>>> [<ffffffff802a1c53>] get_user_pages+0x2f5/0x3eb
>>> [<ffffffff802a1f64>] make_pages_present+0x9e/0xca
>>> [<ffffffff802a51fc>] mmap_region+0x38c/0x452
>>> [<ffffffff802119c4>] arch_get_unmapped_area_topdown+0x1bf/0x2a7
>>> [<ffffffff802a5971>] do_mmap_pgoff+0x321/0x39b
>>> [<ffffffff805037ee>] _cond_resched+0x1c/0x5f
>>> [<ffffffff80211715>] sys_mmap+0xf5/0x138
>>> [<ffffffff8020c6d2>] tracesys+0xd5/0xda
>>> ---[ end trace fe959fb2f0473e7c ]---
>>> tried to kill an mm-less task!
>>>
>>> This showed up several times in some seconds, but then didn't appear
>>> any more. And it's reproducable in a x86_64 box, but doesn't happen
>>> in a x86_32 one.
>>>
>>> And this happens both with and without the oops fixing.
>>>
>> Could we get some more details on which task was chosen to be killed? It will be
>> nice to see the task flags as well to see if PF_EXITING is set.
>>
>> oom_kill_task() has a big WARNING in the comment
>>
>> /* WARNING: mm may not be dereferenced since we did not obtain its
>> * value from get_task_mm(p). This is OK since all we need to do is
>> * compare mm to q->mm below.
>>
>>
>> I want to see the flags to see if
>>
>> PF_BORROWED_MM or PF_EXIT* is set.
>>
>>
>
> OK, I'll try.
>
> --
I Added 2 printk()s:
static void __oom_kill_task(struct task_struct *p, int verbose)
{
+ printk(KERN_WARNING "pid = %d, flags = %x\n", p->pid, p->flags);
+
if (is_global_init(p)) {
WARN_ON(1);
printk(KERN_WARNING "tried to kill init!\n");
@@ -319,6 +320,7 @@ static void __oom_kill_task(struct task_struct *p, int verbo
if (!p->mm) {
WARN_ON(1);
+ printk(KERN_WARNING "pid = %d, flags = %x\n", p->pid, p->flags);
printk(KERN_WARNING "tried to kill an mm-less task!\n");
return;
}
got this:
pid = 3817, flags = 400140
------------[ cut here ]------------
WARNING: at mm/oom_kill.c:322 __oom_kill_task+0x74/0xf1()
...
---[ end trace bb92f2fd8fe6c7c5 ]---
pid = 3817, flags = 400144
tried to kill an mm-less task!
So PF_EXITING may be set during the call of oom_kill_task(), and I notice
the comment in oom_kill_task():
* Furthermore, even if mm contains a non-NULL value, p->mm may
* change to NULL at any time since we do not hold task_lock(p).
* However, this is of no concern to us.
Is this warning just harmless so that we can just ignore it ?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
2008-04-15 3:47 ` Li Zefan
@ 2008-04-15 6:17 ` Oleg Nesterov
-1 siblings, 0 replies; 18+ messages in thread
From: Oleg Nesterov @ 2008-04-15 6:17 UTC (permalink / raw
To: Li Zefan
Cc: balbir, linux-mm@kvack.org, LKML, Andrew Morton,
KAMEZAWA Hiroyuki, Pavel Emelianov, Roland McGrath
(cc Roland)
On 04/15, Li Zefan wrote:
>
> Li Zefan wrote:
> > Balbir Singh wrote:
> >> Li Zefan wrote:
> >>> When I ran the same test program I described in a previous patch,
> >>> I got the following warning:
> >>>
> >>> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
> >>> Modules linked in:
> >>>
>
> I Added 2 printk()s:
>
> static void __oom_kill_task(struct task_struct *p, int verbose)
> {
> + printk(KERN_WARNING "pid = %d, flags = %x\n", p->pid, p->flags);
> +
> if (is_global_init(p)) {
> WARN_ON(1);
> printk(KERN_WARNING "tried to kill init!\n");
> @@ -319,6 +320,7 @@ static void __oom_kill_task(struct task_struct *p, int verbo
>
> if (!p->mm) {
> WARN_ON(1);
> + printk(KERN_WARNING "pid = %d, flags = %x\n", p->pid, p->flags);
> printk(KERN_WARNING "tried to kill an mm-less task!\n");
> return;
> }
>
> got this:
>
> pid = 3817, flags = 400140
> ------------[ cut here ]------------
> WARNING: at mm/oom_kill.c:322 __oom_kill_task+0x74/0xf1()
> ...
> ---[ end trace bb92f2fd8fe6c7c5 ]---
> pid = 3817, flags = 400144
> tried to kill an mm-less task!
>
> So PF_EXITING may be set during the call of oom_kill_task(), and I notice
> the comment in oom_kill_task():
>
> * Furthermore, even if mm contains a non-NULL value, p->mm may
> * change to NULL at any time since we do not hold task_lock(p).
> * However, this is of no concern to us.
>
> Is this warning just harmless so that we can just ignore it ?
Yes sure, tasklist_lock can't prevent the task exiting, it only protects
from release_task(). And task->mm == NULL after do_exit()->exit_mm().
Perhaps we can check "!p->mm && !PF_EXITING".
I don't think we should check PF_BORROWED_MM in __oom_kill_task(), it is
too late.
Perhaps,
--- fs/aio.c 2008-02-17 23:40:07.000000000 +0300
+++ fs/aio.c 2008-04-15 09:31:23.841202187 +0400
@@ -579,6 +579,7 @@ static void use_mm(struct mm_struct *mm)
task_lock(tsk);
tsk->flags |= PF_BORROWED_MM;
+ smp_wmb();
active_mm = tsk->active_mm;
atomic_inc(&mm->mm_count);
tsk->mm = mm;
@@ -606,13 +607,23 @@ static void unuse_mm(struct mm_struct *m
struct task_struct *tsk = current;
task_lock(tsk);
- tsk->flags &= ~PF_BORROWED_MM;
tsk->mm = NULL;
+ smp_wmb();
+ tsk->flags &= ~PF_BORROWED_MM;
/* active_mm is still 'mm' */
enter_lazy_tlb(mm, tsk);
task_unlock(tsk);
}
+struct mm_struct *__get_task_mm(struct task_struct *tsk)
+{
+ struct mm_struct *mm = tsk->mm;
+ smp_rmb();
+ if (tsk->flags & PF_BORROWED_MM)
+ mm = NULL;
+ return mm;
+}
+
/*
* Queue up a kiocb to be retried. Assumes that the kiocb
* has already been marked as kicked, and places it on
Now oom_kill_task/select_bad_process/etc can use __get_task_mm() to avoid
killing the kernel thread.
Off-topic: why ->oomkilladj is per thread, not per process? All threads share
the same ->mm. Note oom_kill_process(), it shouldn't use do_each_thread(),
it actually needs for_each_process().
Roland, what do you think about the coredump? Looks like we have the ancient
bug, zap_threads() can hit the kernel thread.
How about
--- fs/exec.c 2008-02-17 23:40:07.000000000 +0300
+++ fs/exec.c 2008-04-15 10:07:08.998518272 +0400
@@ -1547,7 +1547,7 @@ static inline int zap_threads(struct tas
p = g;
do {
if (p->mm) {
- if (p->mm == mm) {
+ if (__get_task_mm(p) == mm) {
/*
* p->sighand can't disappear, but
* may be changed by de_thread()
?
Oleg.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
@ 2008-04-15 6:17 ` Oleg Nesterov
0 siblings, 0 replies; 18+ messages in thread
From: Oleg Nesterov @ 2008-04-15 6:17 UTC (permalink / raw
To: Li Zefan
Cc: balbir, linux-mm@kvack.org, LKML, Andrew Morton,
KAMEZAWA Hiroyuki, Pavel Emelianov, Roland McGrath
(cc Roland)
On 04/15, Li Zefan wrote:
>
> Li Zefan wrote:
> > Balbir Singh wrote:
> >> Li Zefan wrote:
> >>> When I ran the same test program I described in a previous patch,
> >>> I got the following warning:
> >>>
> >>> WARNING: at mm/oom_kill.c:320 __oom_kill_task+0x6d/0x101()
> >>> Modules linked in:
> >>>
>
> I Added 2 printk()s:
>
> static void __oom_kill_task(struct task_struct *p, int verbose)
> {
> + printk(KERN_WARNING "pid = %d, flags = %x\n", p->pid, p->flags);
> +
> if (is_global_init(p)) {
> WARN_ON(1);
> printk(KERN_WARNING "tried to kill init!\n");
> @@ -319,6 +320,7 @@ static void __oom_kill_task(struct task_struct *p, int verbo
>
> if (!p->mm) {
> WARN_ON(1);
> + printk(KERN_WARNING "pid = %d, flags = %x\n", p->pid, p->flags);
> printk(KERN_WARNING "tried to kill an mm-less task!\n");
> return;
> }
>
> got this:
>
> pid = 3817, flags = 400140
> ------------[ cut here ]------------
> WARNING: at mm/oom_kill.c:322 __oom_kill_task+0x74/0xf1()
> ...
> ---[ end trace bb92f2fd8fe6c7c5 ]---
> pid = 3817, flags = 400144
> tried to kill an mm-less task!
>
> So PF_EXITING may be set during the call of oom_kill_task(), and I notice
> the comment in oom_kill_task():
>
> * Furthermore, even if mm contains a non-NULL value, p->mm may
> * change to NULL at any time since we do not hold task_lock(p).
> * However, this is of no concern to us.
>
> Is this warning just harmless so that we can just ignore it ?
Yes sure, tasklist_lock can't prevent the task exiting, it only protects
from release_task(). And task->mm == NULL after do_exit()->exit_mm().
Perhaps we can check "!p->mm && !PF_EXITING".
I don't think we should check PF_BORROWED_MM in __oom_kill_task(), it is
too late.
Perhaps,
--- fs/aio.c 2008-02-17 23:40:07.000000000 +0300
+++ fs/aio.c 2008-04-15 09:31:23.841202187 +0400
@@ -579,6 +579,7 @@ static void use_mm(struct mm_struct *mm)
task_lock(tsk);
tsk->flags |= PF_BORROWED_MM;
+ smp_wmb();
active_mm = tsk->active_mm;
atomic_inc(&mm->mm_count);
tsk->mm = mm;
@@ -606,13 +607,23 @@ static void unuse_mm(struct mm_struct *m
struct task_struct *tsk = current;
task_lock(tsk);
- tsk->flags &= ~PF_BORROWED_MM;
tsk->mm = NULL;
+ smp_wmb();
+ tsk->flags &= ~PF_BORROWED_MM;
/* active_mm is still 'mm' */
enter_lazy_tlb(mm, tsk);
task_unlock(tsk);
}
+struct mm_struct *__get_task_mm(struct task_struct *tsk)
+{
+ struct mm_struct *mm = tsk->mm;
+ smp_rmb();
+ if (tsk->flags & PF_BORROWED_MM)
+ mm = NULL;
+ return mm;
+}
+
/*
* Queue up a kiocb to be retried. Assumes that the kiocb
* has already been marked as kicked, and places it on
Now oom_kill_task/select_bad_process/etc can use __get_task_mm() to avoid
killing the kernel thread.
Off-topic: why ->oomkilladj is per thread, not per process? All threads share
the same ->mm. Note oom_kill_process(), it shouldn't use do_each_thread(),
it actually needs for_each_process().
Roland, what do you think about the coredump? Looks like we have the ancient
bug, zap_threads() can hit the kernel thread.
How about
--- fs/exec.c 2008-02-17 23:40:07.000000000 +0300
+++ fs/exec.c 2008-04-15 10:07:08.998518272 +0400
@@ -1547,7 +1547,7 @@ static inline int zap_threads(struct tas
p = g;
do {
if (p->mm) {
- if (p->mm == mm) {
+ if (__get_task_mm(p) == mm) {
/*
* p->sighand can't disappear, but
* may be changed by de_thread()
?
Oleg.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 18+ messages in thread
* s/PF_BORROWED_MM/PF_KTHREAD/ (was: kernel warning: tried to kill an mm-less task!)
2008-04-15 6:17 ` Oleg Nesterov
@ 2008-04-15 10:19 ` Oleg Nesterov
-1 siblings, 0 replies; 18+ messages in thread
From: Oleg Nesterov @ 2008-04-15 10:19 UTC (permalink / raw
To: Li Zefan
Cc: balbir, linux-mm@kvack.org, LKML, Andrew Morton,
KAMEZAWA Hiroyuki, Pavel Emelianov, Roland McGrath, Jeff Dike
On 04/15, Oleg Nesterov wrote:
>
> +struct mm_struct *__get_task_mm(struct task_struct *tsk)
> +{
> + struct mm_struct *mm = tsk->mm;
> + smp_rmb();
> + if (tsk->flags & PF_BORROWED_MM)
> + mm = NULL;
> + return mm;
> +}
No, this is racy wrt unuse_mm(), we still need task_lock().
Actually, I think PF_BORROWED_MM should die, and PF_I_AM_A_KERNEL_THREAD
is better, see the "patch" below.
First, include/asm-um/mmu_context.h:activate_mm() doesn't look right to me,
use_mm() does switch_mm(), not activate_mm(), so I think we can do
--- include/asm-um/mmu_context.h 2008-02-17 23:40:08.000000000 +0300
+++ - 2008-04-15 13:35:34.089295980 +0400
@@ -29,7 +29,7 @@ static inline void activate_mm(struct mm
* host. Since they're very expensive, we want to avoid that as far as
* possible.
*/
- if (old != new && (current->flags & PF_BORROWED_MM))
+ if (old != new)
__switch_mm(&new->context.id);
arch_dup_mmap(old, new);
With this + patch below, we can make a simple helper,
/* The result must not be dereferenced !!! */
struct mm_struct *__get_task_mm(struct task_struct *tsk)
{
if (tsk->flags & PF_KTHREAD)
return NULL;
return tsk->mm;
}
it could ve used by oom_kill/coredump/ptrace_attach instead of "->mm != NULL"
which doesn't really work. Note also that ecard_task() runs with mm != NULL,
but it is the kernel thread without PF_BORROWED_MM.
daemonize() is racy, but it is hopeless anyway.
Oleg.
--- include/linux/sched.h 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 11:38:46.892847693 +0400
@@ -1458,7 +1458,7 @@ static inline void put_task_struct(struc
#define PF_KSWAPD 0x00040000 /* I am kswapd */
#define PF_SWAPOFF 0x00080000 /* I am in swapoff */
#define PF_LESS_THROTTLE 0x00100000 /* Throttle me less: I clean memory */
-#define PF_BORROWED_MM 0x00200000 /* I am a kthread doing use_mm */
+#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
#define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */
#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
#define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */
--- kernel/power/process.c 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 11:41:13.044031366 +0400
@@ -93,7 +93,7 @@ static void send_fake_signal(struct task
static int has_mm(struct task_struct *p)
{
- return (p->mm && !(p->flags & PF_BORROWED_MM));
+ return (p->mm && !(p->flags & PF_KTHREAD));
}
/**
--- fs/aio.c 2008-02-17 23:40:07.000000000 +0300
+++ - 2008-04-15 11:44:11.100698248 +0400
@@ -578,15 +578,10 @@ static void use_mm(struct mm_struct *mm)
struct task_struct *tsk = current;
task_lock(tsk);
- tsk->flags |= PF_BORROWED_MM;
active_mm = tsk->active_mm;
atomic_inc(&mm->mm_count);
tsk->mm = mm;
tsk->active_mm = mm;
- /*
- * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
- * it won't work. Update it accordingly if you change it here
- */
switch_mm(active_mm, mm, tsk);
task_unlock(tsk);
@@ -606,7 +601,6 @@ static void unuse_mm(struct mm_struct *m
struct task_struct *tsk = current;
task_lock(tsk);
- tsk->flags &= ~PF_BORROWED_MM;
tsk->mm = NULL;
/* active_mm is still 'mm' */
enter_lazy_tlb(mm, tsk);
--- kernel/fork.c 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 11:48:24.539070614 +0400
@@ -424,7 +424,7 @@ EXPORT_SYMBOL_GPL(mmput);
/**
* get_task_mm - acquire a reference to the task's mm
*
- * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
+ * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
* this kernel workthread has transiently adopted a user mm with use_mm,
* to do its AIO) is not set and if so returns a reference to it, after
* bumping up the use count. User must release the mm via mmput()
@@ -437,7 +437,7 @@ struct mm_struct *get_task_mm(struct tas
task_lock(task);
mm = task->mm;
if (mm) {
- if (task->flags & PF_BORROWED_MM)
+ if (task->flags & PF_KTHREAD)
mm = NULL;
else
atomic_inc(&mm->mm_users);
--- kernel/kthread.c 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 11:51:06.014085477 +0400
@@ -234,7 +234,7 @@ int kthreadd(void *unused)
set_user_nice(tsk, KTHREAD_NICE_LEVEL);
set_cpus_allowed(tsk, CPU_MASK_ALL);
- current->flags |= PF_NOFREEZE;
+ current->flags |= (PF_NOFREEZE | PF_KTHREAD);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
--- fs/exec.c 2008-02-17 23:40:07.000000000 +0300
+++ - 2008-04-15 12:33:10.854945536 +0400
@@ -1328,6 +1328,7 @@ int do_execve(char * filename,
goto out;
bprm->argv_len = env_p - bprm->p;
+ current->flags &= ~PF_KTHREAD;
retval = search_binary_handler(bprm,regs);
if (retval >= 0) {
/* execve success */
--- kernel/exit.c 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 13:49:30.916850385 +0400
@@ -382,7 +382,7 @@ void daemonize(const char *name, ...)
* We don't want to have TIF_FREEZE set if the system-wide hibernation
* or suspend transition begins right now.
*/
- current->flags |= PF_NOFREEZE;
+ current->flags |= (PF_NOFREEZE | PF_KTHREAD);
if (current->nsproxy != &init_nsproxy) {
get_nsproxy(&init_nsproxy);
^ permalink raw reply [flat|nested] 18+ messages in thread
* s/PF_BORROWED_MM/PF_KTHREAD/ (was: kernel warning: tried to kill an mm-less task!)
@ 2008-04-15 10:19 ` Oleg Nesterov
0 siblings, 0 replies; 18+ messages in thread
From: Oleg Nesterov @ 2008-04-15 10:19 UTC (permalink / raw
To: Li Zefan
Cc: balbir, linux-mm@kvack.org, LKML, Andrew Morton,
KAMEZAWA Hiroyuki, Pavel Emelianov, Roland McGrath, Jeff Dike
On 04/15, Oleg Nesterov wrote:
>
> +struct mm_struct *__get_task_mm(struct task_struct *tsk)
> +{
> + struct mm_struct *mm = tsk->mm;
> + smp_rmb();
> + if (tsk->flags & PF_BORROWED_MM)
> + mm = NULL;
> + return mm;
> +}
No, this is racy wrt unuse_mm(), we still need task_lock().
Actually, I think PF_BORROWED_MM should die, and PF_I_AM_A_KERNEL_THREAD
is better, see the "patch" below.
First, include/asm-um/mmu_context.h:activate_mm() doesn't look right to me,
use_mm() does switch_mm(), not activate_mm(), so I think we can do
--- include/asm-um/mmu_context.h 2008-02-17 23:40:08.000000000 +0300
+++ - 2008-04-15 13:35:34.089295980 +0400
@@ -29,7 +29,7 @@ static inline void activate_mm(struct mm
* host. Since they're very expensive, we want to avoid that as far as
* possible.
*/
- if (old != new && (current->flags & PF_BORROWED_MM))
+ if (old != new)
__switch_mm(&new->context.id);
arch_dup_mmap(old, new);
With this + patch below, we can make a simple helper,
/* The result must not be dereferenced !!! */
struct mm_struct *__get_task_mm(struct task_struct *tsk)
{
if (tsk->flags & PF_KTHREAD)
return NULL;
return tsk->mm;
}
it could ve used by oom_kill/coredump/ptrace_attach instead of "->mm != NULL"
which doesn't really work. Note also that ecard_task() runs with mm != NULL,
but it is the kernel thread without PF_BORROWED_MM.
daemonize() is racy, but it is hopeless anyway.
Oleg.
--- include/linux/sched.h 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 11:38:46.892847693 +0400
@@ -1458,7 +1458,7 @@ static inline void put_task_struct(struc
#define PF_KSWAPD 0x00040000 /* I am kswapd */
#define PF_SWAPOFF 0x00080000 /* I am in swapoff */
#define PF_LESS_THROTTLE 0x00100000 /* Throttle me less: I clean memory */
-#define PF_BORROWED_MM 0x00200000 /* I am a kthread doing use_mm */
+#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
#define PF_RANDOMIZE 0x00400000 /* randomize virtual address space */
#define PF_SWAPWRITE 0x00800000 /* Allowed to write to swap */
#define PF_SPREAD_PAGE 0x01000000 /* Spread page cache over cpuset */
--- kernel/power/process.c 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 11:41:13.044031366 +0400
@@ -93,7 +93,7 @@ static void send_fake_signal(struct task
static int has_mm(struct task_struct *p)
{
- return (p->mm && !(p->flags & PF_BORROWED_MM));
+ return (p->mm && !(p->flags & PF_KTHREAD));
}
/**
--- fs/aio.c 2008-02-17 23:40:07.000000000 +0300
+++ - 2008-04-15 11:44:11.100698248 +0400
@@ -578,15 +578,10 @@ static void use_mm(struct mm_struct *mm)
struct task_struct *tsk = current;
task_lock(tsk);
- tsk->flags |= PF_BORROWED_MM;
active_mm = tsk->active_mm;
atomic_inc(&mm->mm_count);
tsk->mm = mm;
tsk->active_mm = mm;
- /*
- * Note that on UML this *requires* PF_BORROWED_MM to be set, otherwise
- * it won't work. Update it accordingly if you change it here
- */
switch_mm(active_mm, mm, tsk);
task_unlock(tsk);
@@ -606,7 +601,6 @@ static void unuse_mm(struct mm_struct *m
struct task_struct *tsk = current;
task_lock(tsk);
- tsk->flags &= ~PF_BORROWED_MM;
tsk->mm = NULL;
/* active_mm is still 'mm' */
enter_lazy_tlb(mm, tsk);
--- kernel/fork.c 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 11:48:24.539070614 +0400
@@ -424,7 +424,7 @@ EXPORT_SYMBOL_GPL(mmput);
/**
* get_task_mm - acquire a reference to the task's mm
*
- * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
+ * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
* this kernel workthread has transiently adopted a user mm with use_mm,
* to do its AIO) is not set and if so returns a reference to it, after
* bumping up the use count. User must release the mm via mmput()
@@ -437,7 +437,7 @@ struct mm_struct *get_task_mm(struct tas
task_lock(task);
mm = task->mm;
if (mm) {
- if (task->flags & PF_BORROWED_MM)
+ if (task->flags & PF_KTHREAD)
mm = NULL;
else
atomic_inc(&mm->mm_users);
--- kernel/kthread.c 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 11:51:06.014085477 +0400
@@ -234,7 +234,7 @@ int kthreadd(void *unused)
set_user_nice(tsk, KTHREAD_NICE_LEVEL);
set_cpus_allowed(tsk, CPU_MASK_ALL);
- current->flags |= PF_NOFREEZE;
+ current->flags |= (PF_NOFREEZE | PF_KTHREAD);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
--- fs/exec.c 2008-02-17 23:40:07.000000000 +0300
+++ - 2008-04-15 12:33:10.854945536 +0400
@@ -1328,6 +1328,7 @@ int do_execve(char * filename,
goto out;
bprm->argv_len = env_p - bprm->p;
+ current->flags &= ~PF_KTHREAD;
retval = search_binary_handler(bprm,regs);
if (retval >= 0) {
/* execve success */
--- kernel/exit.c 2008-02-17 23:40:09.000000000 +0300
+++ - 2008-04-15 13:49:30.916850385 +0400
@@ -382,7 +382,7 @@ void daemonize(const char *name, ...)
* We don't want to have TIF_FREEZE set if the system-wide hibernation
* or suspend transition begins right now.
*/
- current->flags |= PF_NOFREEZE;
+ current->flags |= (PF_NOFREEZE | PF_KTHREAD);
if (current->nsproxy != &init_nsproxy) {
get_nsproxy(&init_nsproxy);
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: s/PF_BORROWED_MM/PF_KTHREAD/ (was: kernel warning: tried to kill an mm-less task!)
2008-04-15 10:19 ` Oleg Nesterov
@ 2008-04-15 17:10 ` Jeff Dike
-1 siblings, 0 replies; 18+ messages in thread
From: Jeff Dike @ 2008-04-15 17:10 UTC (permalink / raw
To: Oleg Nesterov
Cc: Li Zefan, balbir, linux-mm@kvack.org, LKML, Andrew Morton,
KAMEZAWA Hiroyuki, Pavel Emelianov, Roland McGrath
On Tue, Apr 15, 2008 at 02:19:05PM +0400, Oleg Nesterov wrote:
> First, include/asm-um/mmu_context.h:activate_mm() doesn't look right to me,
> use_mm() does switch_mm(), not activate_mm(), so I think we can do
>
> --- include/asm-um/mmu_context.h 2008-02-17 23:40:08.000000000 +0300
> +++ - 2008-04-15 13:35:34.089295980 +0400
> @@ -29,7 +29,7 @@ static inline void activate_mm(struct mm
> * host. Since they're very expensive, we want to avoid that as far as
> * possible.
> */
> - if (old != new && (current->flags & PF_BORROWED_MM))
> + if (old != new)
> __switch_mm(&new->context.id);
>
> arch_dup_mmap(old, new);
I'm thinking I can just change this to call switch_mm, getting rid of
the old != new test too.
Plus, you can get rid of the comment in use_mm about UML needing
PF_BORROWED_MM.
I'll test this to make sure.
Jeff
--
Work email - jdike at linux dot intel dot com
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: s/PF_BORROWED_MM/PF_KTHREAD/ (was: kernel warning: tried to kill an mm-less task!)
@ 2008-04-15 17:10 ` Jeff Dike
0 siblings, 0 replies; 18+ messages in thread
From: Jeff Dike @ 2008-04-15 17:10 UTC (permalink / raw
To: Oleg Nesterov
Cc: Li Zefan, balbir, linux-mm@kvack.org, LKML, Andrew Morton,
KAMEZAWA Hiroyuki, Pavel Emelianov, Roland McGrath
On Tue, Apr 15, 2008 at 02:19:05PM +0400, Oleg Nesterov wrote:
> First, include/asm-um/mmu_context.h:activate_mm() doesn't look right to me,
> use_mm() does switch_mm(), not activate_mm(), so I think we can do
>
> --- include/asm-um/mmu_context.h 2008-02-17 23:40:08.000000000 +0300
> +++ - 2008-04-15 13:35:34.089295980 +0400
> @@ -29,7 +29,7 @@ static inline void activate_mm(struct mm
> * host. Since they're very expensive, we want to avoid that as far as
> * possible.
> */
> - if (old != new && (current->flags & PF_BORROWED_MM))
> + if (old != new)
> __switch_mm(&new->context.id);
>
> arch_dup_mmap(old, new);
I'm thinking I can just change this to call switch_mm, getting rid of
the old != new test too.
Plus, you can get rid of the comment in use_mm about UML needing
PF_BORROWED_MM.
I'll test this to make sure.
Jeff
--
Work email - jdike at linux dot intel dot com
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
2008-04-15 6:17 ` Oleg Nesterov
@ 2008-04-15 20:58 ` Roland McGrath
-1 siblings, 0 replies; 18+ messages in thread
From: Roland McGrath @ 2008-04-15 20:58 UTC (permalink / raw
To: Oleg Nesterov
Cc: Li Zefan, balbir, linux-mm@kvack.org, LKML, Andrew Morton,
KAMEZAWA Hiroyuki, Pavel Emelianov
> Roland, what do you think about the coredump? Looks like we have the ancient
> bug, zap_threads() can hit the kernel thread.
I think you're right. But I've never known much about the ->mm maintenance
code or the aio use_mm logic. So I'm just going from a quick glance.
(That part of the zap_threads() logic predates you or I fiddling with it.)
Thanks,
Roland
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: kernel warning: tried to kill an mm-less task!
@ 2008-04-15 20:58 ` Roland McGrath
0 siblings, 0 replies; 18+ messages in thread
From: Roland McGrath @ 2008-04-15 20:58 UTC (permalink / raw
To: Oleg Nesterov
Cc: Li Zefan, balbir, linux-mm@kvack.org, LKML, Andrew Morton,
KAMEZAWA Hiroyuki, Pavel Emelianov
> Roland, what do you think about the coredump? Looks like we have the ancient
> bug, zap_threads() can hit the kernel thread.
I think you're right. But I've never known much about the ->mm maintenance
code or the aio use_mm logic. So I'm just going from a quick glance.
(That part of the zap_threads() logic predates you or I fiddling with it.)
Thanks,
Roland
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 18+ messages in thread
end of thread, other threads:[~2008-04-15 20:59 UTC | newest]
Thread overview: 18+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2008-04-14 7:09 kernel warning: tried to kill an mm-less task! Li Zefan
2008-04-14 7:09 ` Li Zefan
2008-04-14 7:46 ` KAMEZAWA Hiroyuki
2008-04-14 7:46 ` KAMEZAWA Hiroyuki
2008-04-14 8:01 ` Balbir Singh
2008-04-14 8:01 ` Balbir Singh
2008-04-14 8:06 ` Li Zefan
2008-04-14 8:06 ` Li Zefan
2008-04-15 3:47 ` Li Zefan
2008-04-15 3:47 ` Li Zefan
2008-04-15 6:17 ` Oleg Nesterov
2008-04-15 6:17 ` Oleg Nesterov
2008-04-15 10:19 ` s/PF_BORROWED_MM/PF_KTHREAD/ (was: kernel warning: tried to kill an mm-less task!) Oleg Nesterov
2008-04-15 10:19 ` Oleg Nesterov
2008-04-15 17:10 ` Jeff Dike
2008-04-15 17:10 ` Jeff Dike
2008-04-15 20:58 ` kernel warning: tried to kill an mm-less task! Roland McGrath
2008-04-15 20:58 ` Roland McGrath
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