linux-kernel - Re: [PATCH -stable] block: fix ext_dev

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Message-ID: <5579A2E7.9030302@kernel.dk>
Date:	Thu, 11 Jun 2015 09:01:59 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Dan Williams <dan.j.williams@...el.com>,
	Jiri Slaby <jslaby@...e.cz>
CC:	Keith Busch <keith.busch@...el.com>, Neil Brown <neilb@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH -stable] block: fix ext_dev_lock lockdep report

On 06/11/2015 08:07 AM, Dan Williams wrote:
> On Thu, Jun 11, 2015 at 12:51 AM, Jiri Slaby <jslaby@...e.cz> wrote:
>> On 06/11/2015, 05:47 AM, Dan Williams wrote:
>>>   =================================
>>>   [ INFO: inconsistent lock state ]
>>>   4.1.0-rc7+ #217 Tainted: G           O
>>>   ---------------------------------
>>>   inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
>>>   swapper/6/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
>>>    (ext_devt_lock){+.?...}, at: [<ffffffff8143a60c>] blk_free_devt+0x3c/0x70
>>>   {SOFTIRQ-ON-W} state was registered at:
>>>     [<ffffffff810bf6b1>] __lock_acquire+0x461/0x1e70
>>>     [<ffffffff810c1947>] lock_acquire+0xb7/0x290
>>>     [<ffffffff818ac3a8>] _raw_spin_lock+0x38/0x50
>>>     [<ffffffff8143a07d>] blk_alloc_devt+0x6d/0xd0  <-- take the lock in process context
>>> [..]
>>>    [<ffffffff810bf64e>] __lock_acquire+0x3fe/0x1e70
>>>    [<ffffffff810c00ad>] ? __lock_acquire+0xe5d/0x1e70
>>>    [<ffffffff810c1947>] lock_acquire+0xb7/0x290
>>>    [<ffffffff8143a60c>] ? blk_free_devt+0x3c/0x70
>>>    [<ffffffff818ac3a8>] _raw_spin_lock+0x38/0x50
>>>    [<ffffffff8143a60c>] ? blk_free_devt+0x3c/0x70
>>>    [<ffffffff8143a60c>] blk_free_devt+0x3c/0x70    <-- take the lock in softirq
>>>    [<ffffffff8143bfec>] part_release+0x1c/0x50
>>>    [<ffffffff8158edf6>] device_release+0x36/0xb0
>>>    [<ffffffff8145ac2b>] kobject_cleanup+0x7b/0x1a0
>>>    [<ffffffff8145aad0>] kobject_put+0x30/0x70
>>>    [<ffffffff8158f147>] put_device+0x17/0x20
>>>    [<ffffffff8143c29c>] delete_partition_rcu_cb+0x16c/0x180
>>>    [<ffffffff8143c130>] ? read_dev_sector+0xa0/0xa0
>>>    [<ffffffff810e0e0f>] rcu_process_callbacks+0x2ff/0xa90
>>>    [<ffffffff810e0dcf>] ? rcu_process_callbacks+0x2bf/0xa90
>>>    [<ffffffff81067e2e>] __do_softirq+0xde/0x600
>>>
>>> Neil sees this in his tests and it also triggers on pmem driver unbind
>>> for the libnvdimm tests.  This fix is on top of an initial fix by Keith
>>> for incorrect usage of mutex_lock() in this path: 2da78092dda1 "block:
>>> Fix dev_t minor allocation lifetime".  Both this and 2da78092dda1 are
>>> candidates for -stable.
>>
>> And what is *this* in terms of SHA? Thanks.
>
> Whatever it becomes when applied by Jens, i.e. self-referencing.

4d66e5e9b6d720d8463e11d027bd4ad91c8b1318

-- 
Jens Axboe

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