linux-kernel - Re: [PATCH 1/3] drm: kill BKL from common code

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Message-ID: <m262yzyhkf.fsf@igel.home>
Date:	Tue, 24 Aug 2010 20:46:40 +0200
From:	Andreas Schwab <schwab@...ux-m68k.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-kernel@...r.kernel.org, John Kacur <jkacur@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 1/3] drm: kill BKL from common code

Arnd Bergmann <arnd@...db.de> writes:

> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 4a66201..76d98f4 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -506,9 +506,9 @@ long drm_ioctl(struct file *filp,
>  		if (ioctl->flags & DRM_UNLOCKED)
>  			retcode = func(dev, kdata, file_priv);
>  		else {
> -			lock_kernel();
> +			mutex_lock(&drm_global_mutex);
>  			retcode = func(dev, kdata, file_priv);
> -			unlock_kernel();
> +			mutex_unlock(&drm_global_mutex);

How is this supposed to work in the context of sleeping ioctls, like
drm_lock?

[drm:drm_ioctl], pid=2461, cmd=0x8008642a, nr=0x2a, dev 0xe200, auth=1
[drm:drm_lock], 1 (pid 2461) requests lock (0x80000003), flags = 0x00000000
[drm:drm_ioctl], pid=2520, cmd=0x8008642b, nr=0x2b, dev 0xe200, auth=1

# ps 2461 2520
  PID TTY      STAT   TIME COMMAND
 2461 tty7     Ss+    0:01 /usr/bin/Xorg -br :0 vt7 -nolisten tcp -auth /var/lib
 2520 pts/2    D+     0:00 glxgears

Andreas.

-- 
Andreas Schwab, schwab@...ux-m68k.org
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