From mboxrd@z Thu Jan  1 00:00:00 1970
From: Artem Bityutskiy <dedekind1@gmail.com>
Subject: Re: [PATCH 02/10] writeback: switch to per-bdi threads for flushing
 data
Date: Wed, 08 Jul 2009 07:47:36 +0300
Message-ID: <4A5424E8.1070201@gmail.com>
References: <1245926523-21959-1-git-send-email-jens.axboe@oracle.com>	 <1245926523-21959-3-git-send-email-jens.axboe@oracle.com>	 <4A53694D.2010905@gmail.com> <1247014636.2560.539.camel@ymzhang>
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Cc: Jens Axboe <jens.axboe@oracle.com>, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, chris.mason@oracle.com,
	david@fromorbit.com, hch@infradead.org, akpm@linux-foundation.org,
	jack@suse.cz, richard@rsk.demon.co.uk, damien.wyart@free.fr,
	fweisbec@gmail.com, Alan.Brunelle@hp.com
To: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
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In-Reply-To: <1247014636.2560.539.camel@ymzhang>
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Zhang, Yanmin wrote:
>>> +		list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
>>> +			if (bdi->task || !bdi_has_dirty_io(bdi))
>>> +				continue;
>>> +
>>> +			bdi_add_default_flusher_task(bdi);
>>> +		}
>>> +
>>> +		set_current_state(TASK_INTERRUPTIBLE);
>>> +
>> What happens if we are preempted here? Since we have TASK_INTERRUPTI=
BLE
>> state, we will not come back unless some other task wakes us up. Who
>> would wake us up in this case?
> If it's preempted (CONFIG_PREEMPT=3Dy), it will stay in runqueue. Onl=
y when
> it calls schedule initiatively or calls schedule when exiting to user=
 space,
> it will be moved out of runqueue if its state isn't TASK_RUNNING.
>=20
> See flag PREEMPT_ACTIVE.

OK, thanks for the hint!

--=20
Best Regards,
Artem Bityutskiy (=D0=90=D1=80=D1=82=D1=91=D0=BC =D0=91=D0=B8=D1=82=D1=8E=
=D1=86=D0=BA=D0=B8=D0=B9)
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