From mboxrd@z Thu Jan  1 00:00:00 1970
From: j.neuschaefer@gmx.net (Jonathan =?utf-8?Q?Neusch=C3=A4fer?=)
Date: Fri, 7 Oct 2011 18:44:17 +0200
Subject: When is to preempt safe?
In-Reply-To: <CAOXENUj1DAGQ9-=N9VvU-ik9KDaTNHwWqEsDP6RPj=nrBpogQw@mail.gmail.com>
References: <CAOXENUj1DAGQ9-=N9VvU-ik9KDaTNHwWqEsDP6RPj=nrBpogQw@mail.gmail.com>
Message-ID: <20111007164417.GB1475@debian.debian>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

On Fri, Oct 07, 2011 at 07:27:12PM +0800, Parmenides wrote:
> 2. Another statement from Love is that "the kernel can preempt a task
> running in the kernel so long as it does not hold a lock". Why is it
> not safe while kernel code holding lock?

If you preempt while a lock is being held, another task could try to
acquire the same lock, causing a deadlock.

HTH,
	Jonathan Neusch?fer