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From: Rabin Vincent <rabin@rab.in>
To: Chanho Min <chanho0207@gmail.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>,
	Jens Axboe <axboe@kernel.dk>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/backing-dev.c: fix crash when USB/SCSI device is detached
Date: Thu, 19 Jan 2012 01:13:21 +0530	[thread overview]
Message-ID: <CAH+eYFBkm+D_N2tF8F_Pdk8qbVeTFcNefeJ6ROcDW3vLgsCGcw@mail.gmail.com> (raw)
In-Reply-To: <CAOAMb1B7oENhPzgUkFjzuJ0==dnHRJkmHFSq-7QtSGeV6JeBvA@mail.gmail.com>

On Mon, Jan 16, 2012 at 12:04, Chanho Min <chanho0207@gmail.com> wrote:
>> But wait.. Rabin's patch actually fixes the NULL deference in
>> the call
>>
>>        trace_writeback_wake_forker_thread(bdi);
>>
>> The wakeup of the forker thread should be harmless.
>>
> The forker thread shoud not be woken up after the bdi is unregistered.
> Is this also Rabin's intention?
> Also, I'm not sure the wakeup of the forker thread is harmless as bellows.
> ..
> case FORK_THREAD:
> ..
>  task = kthread_create(bdi_writeback_thread, &bdi->wb,
>                      "flush-%s", dev_name(bdi->dev));

By the time the bdi->dev is made NULL, the bdi has been removed from the
bdi_list (in bdi_wb_shutdown()), so even if the forker thread is woken
up after that it will not find the bdi and won't get to this part of the
code.

  reply	other threads:[~2012-01-18 19:44 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-05  8:49 [PATCH] mm/backing-dev.c: fix crash when USB/SCSI device is detached Chanho Min
2012-01-15 10:28 ` Rabin Vincent
2012-01-15 12:58   ` Wu Fengguang
2012-01-15 15:41     ` Rabin Vincent
2012-01-16  2:53       ` Wu Fengguang
2012-01-16  5:28         ` Chanho Min
2012-01-16  5:50           ` Wu Fengguang
2012-01-16  5:53             ` Wu Fengguang
2012-01-16  6:34               ` Chanho Min
2012-01-18 19:43                 ` Rabin Vincent [this message]
2012-01-19 16:50         ` [PATCHv2] backing-dev: fix wakeup timer races with bdi_unregister() Rabin Vincent
2012-01-19 23:46           ` Namjae Jeon
2012-01-20  5:24             ` Rabin Vincent
2012-01-20  6:15               ` Namjae Jeon
2012-01-20 10:03                 ` Rabin Vincent
2012-01-20 11:18                   ` Namjae Jeon
2012-01-20 12:08                     ` Rabin Vincent
2012-01-20 15:04                       ` Namjae Jeon
2012-01-31 13:24           ` Wu Fengguang
     [not found] <004401ccc932$444a0070$ccde0150$@min@lge.com>
2012-01-02  9:57 ` [PATCH] mm/backing-dev.c: fix crash when USB/SCSI device is detached Wu Fengguang
     [not found]   ` <002e01ccc9c7$1928c940$4b7a5bc0$@min@lge.com>
2012-01-03  4:49     ` Wu Fengguang

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