linux-kernel - Re: Sleeping thread not receive signal until it wakes up

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Message-ID: <Pine.LNX.4.61.0703072119290.2448@yvahk01.tjqt.qr>
Date:	Wed, 7 Mar 2007 21:20:33 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	"linux-os (Dick Johnson)" <linux-os@...logic.com>
cc:	Luong Ngo <luong.ngo@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Sleeping thread not receive signal until it wakes up


On Mar 7 2007 08:19, linux-os (Dick Johnson) wrote:
>
>Later versions of the kernel lock the kernel when an ioctl() is
>entered. This means that if you sleep in the ioctl(), nothing
>will get scheduled.

Later versions of the kernel also have an ->unlocked_ioctl method,
which is probably better than below's approach [which is akin to
FreeBSD's DROP_GIANT/PICKUP_GIANT].

>You can do the following (possibly unsafe) in your ioctl():
>
>     int locked = kernel_locked();
>
>     ......... code
>     ......... code
>
>     if(locked)  // Before sleeping section
>        unlock_kernel();
>     .......... sleeping code
>     if(locked)  // After sleeping section
>         lock_kernel();
>
>

Jan
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