From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Michal Hocko <mhocko@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [PATCH] mm/memory-hotplug: Switch locking to a percpu rwsem
Date: Fri, 30 Jun 2017 18:56:44 +0300 [thread overview]
Message-ID: <fc6676da-dc20-a80c-82b3-ae479af3e6ad@virtuozzo.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1706301418190.1748@nanos>
On 06/30/2017 04:00 PM, Thomas Gleixner wrote:
> On Fri, 30 Jun 2017, Andrey Ryabinin wrote:
>> On 06/30/2017 01:15 PM, Thomas Gleixner wrote:
>>> On Fri, 30 Jun 2017, Michal Hocko wrote:
>>>> So I like this simplification a lot! Even if we can get rid of the
>>>> stop_machine eventually this patch would be an improvement. A short
>>>> comment on why the per-cpu semaphore over the regular one is better
>>>> would be nice.
>>>
>>> Yes, will add one.
>>>
>>> The main point is that the current locking construct is evading lockdep due
>>> to the ability to support recursive locking, which I did not observe so
>>> far.
>>>
>>
>> Like this?
>
> Cute.....
>
>> [ 131.023034] Call Trace:
>> [ 131.023034] dump_stack+0x85/0xc7
>> [ 131.023034] __lock_acquire+0x1747/0x17a0
>> [ 131.023034] ? lru_add_drain_all+0x3d/0x190
>> [ 131.023034] ? __mutex_lock+0x218/0x940
>> [ 131.023034] ? trace_hardirqs_on+0xd/0x10
>> [ 131.023034] lock_acquire+0x103/0x200
>> [ 131.023034] ? lock_acquire+0x103/0x200
>> [ 131.023034] ? lru_add_drain_all+0x42/0x190
>> [ 131.023034] cpus_read_lock+0x3d/0x80
>> [ 131.023034] ? lru_add_drain_all+0x42/0x190
>> [ 131.023034] lru_add_drain_all+0x42/0x190
>> [ 131.023034] __offline_pages.constprop.25+0x5de/0x870
>> [ 131.023034] offline_pages+0xc/0x10
>> [ 131.023034] memory_subsys_offline+0x43/0x70
>> [ 131.023034] device_offline+0x83/0xb0
>> [ 131.023034] store_mem_state+0xdb/0xe0
>> [ 131.023034] dev_attr_store+0x13/0x20
>> [ 131.023034] sysfs_kf_write+0x40/0x50
>> [ 131.023034] kernfs_fop_write+0x130/0x1b0
>> [ 131.023034] __vfs_write+0x23/0x130
>> [ 131.023034] ? rcu_read_lock_sched_held+0x6d/0x80
>> [ 131.023034] ? rcu_sync_lockdep_assert+0x2a/0x50
>> [ 131.023034] ? __sb_start_write+0xd4/0x1c0
>> [ 131.023034] ? vfs_write+0x1a8/0x1d0
>> [ 131.023034] vfs_write+0xc8/0x1d0
>> [ 131.023034] SyS_write+0x44/0xa0
>
> Why didn't trigger that here? Bah, I should have become suspicious due to
> not seeing a splat ....
>
> The patch below should cure that.
>
FWIW, it works for me.
> Thanks,
>
> tglx
>
next prev parent reply other threads:[~2017-06-30 15:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-29 16:11 [PATCH] mm/memory-hotplug: Switch locking to a percpu rwsem Thomas Gleixner
2017-06-30 9:27 ` Michal Hocko
2017-06-30 10:15 ` Thomas Gleixner
2017-06-30 11:49 ` Andrey Ryabinin
2017-06-30 13:00 ` Thomas Gleixner
2017-06-30 15:56 ` Andrey Ryabinin [this message]
2017-07-03 16:32 ` Michal Hocko
2017-07-03 19:57 ` Thomas Gleixner
2017-07-03 12:41 ` Vladimir Davydov
2017-07-03 16:38 ` Michal Hocko
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