From: Jens Axboe <axboe@suse.de>
To: Ming Zhang <mingz@ele.uri.edu>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: can generic_make_request in 2.4 kernel sleep?
Date: Sun, 29 Feb 2004 10:49:45 +0100 [thread overview]
Message-ID: <20040229094945.GG3149@suse.de> (raw)
In-Reply-To: <1077984402.4422.36.camel@localhost.localdomain>
On Sat, Feb 28 2004, Ming Zhang wrote:
> Hi, I have a quick question.
>
> In 2.4 kernel, can generic_make_request sleep?
yes
> I read the 2.4.24 kernel and find that there is printk in it. so i
> assume it can sleep. if so, why the per queue make_request_fn can not
> sleep base on the LDD book? and i do not see any place that the
> io_request_lock is held. is this lock removed from system? or we do not
> need this lock at this place any more?
>
> and in md code, it use blk_queue_make_request to use its own request_fn
> instead a queue, for example, in raid1_make_request(), it calls
> raid1_alloc_r1ch() which also call schedule() if need, then this own
> request_fn can sleep?
>
> i think i am little confused about the LDD (linux device driver 2nd)
> book and the new kernel code. can anybody point out some latest
> reference for me?
->make_request_fn() is not entered with the queue/io_request_lock. It
can sleep, it's not recommended since on writeout you are blocking
kswapd/bdflush.
--
Jens Axboe
prev parent reply other threads:[~2004-02-29 9:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-28 16:06 can generic_make_request in 2.4 kernel sleep? Ming Zhang
2004-02-29 9:49 ` Jens Axboe [this message]
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