linux-kernel - Re: [PATCH 8/9] gma500: frame buffer locking

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Date:	Fri, 26 Aug 2011 10:48:14 -0700
From:	Greg KH <greg@...ah.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/9] gma500: frame buffer locking

On Fri, Aug 26, 2011 at 10:45:47AM -0700, Greg KH wrote:
> On Fri, Aug 26, 2011 at 11:19:58AM +0100, Alan Cox wrote:
> > From: Alan Cox <alan@...ux.intel.com>
> > 
> > If we are the console then a printk can hit us with a spin lock held (and
> > in fact the kernel will do its best to take printing lock).
> > 
> > In that case we cannot politely sleep when synching after an accelerated op
> > but must behave obnixously to be sure of getting the bits out.
> > 
> > Signed-off-by: Alan Cox <alan@...ux.intel.com>
> > ---
> > 
> >  drivers/staging/gma500/accel_2d.c |   10 ++++++----
> >  drivers/staging/gma500/psb_drv.c  |    2 +-
> >  drivers/staging/gma500/psb_drv.h  |    2 +-
> >  kernel/printk.c                   |    2 +-
> >  4 files changed, 9 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/staging/gma500/accel_2d.c b/drivers/staging/gma500/accel_2d.c
> > index be92371..114b99a 100644
> > --- a/drivers/staging/gma500/accel_2d.c
> > +++ b/drivers/staging/gma500/accel_2d.c
> > @@ -111,8 +111,9 @@ static int psbfb_2d_submit(struct drm_psb_private *dev_priv, uint32_t *cmdbuf,
> >  	int ret = 0;
> >  	int i;
> >  	unsigned submit_size;
> > +	unsigned long flags;
> >  
> > -	mutex_lock(&dev_priv->mutex_2d);
> > +	spin_lock_irqsave(&dev_priv->lock_2d, flags);
> >  	while (size > 0) {
> >  		submit_size = (size < 0x60) ? size : 0x60;
> >  		size -= submit_size;
> > @@ -127,7 +128,7 @@ static int psbfb_2d_submit(struct drm_psb_private *dev_priv, uint32_t *cmdbuf,
> >  
> >  		(void)PSB_RSGX32(PSB_SGX_2D_SLAVE_PORT + i - 4);
> >  	}
> > -	mutex_unlock(&dev_priv->mutex_2d);
> > +	spin_unlock_irqrestore(&dev_priv->lock_2d, flags);
> >  	return ret;
> >  }
> >  
> > @@ -327,8 +328,9 @@ int psbfb_sync(struct fb_info *info)
> >  	struct drm_psb_private *dev_priv = dev->dev_private;
> >  	unsigned long _end = jiffies + DRM_HZ;
> >  	int busy = 0;
> > +	unsigned long flags;
> >  
> > -	mutex_lock(&dev_priv->mutex_2d);
> > +	spin_lock_irqsave(&dev_priv->lock_2d, flags);
> >  	/*
> >  	 * First idle the 2D engine.
> >  	 */
> > @@ -357,7 +359,7 @@ int psbfb_sync(struct fb_info *info)
> >  					_PSB_C2B_STATUS_BUSY) != 0);
> >  
> >  out:
> > -	mutex_unlock(&dev_priv->mutex_2d);
> > +	spin_unlock_irqrestore(&dev_priv->lock_2d, flags);
> >  	return (busy) ? -EBUSY : 0;
> >  }
> >  
> > diff --git a/drivers/staging/gma500/psb_drv.c b/drivers/staging/gma500/psb_drv.c
> > index 34cf24a..9470af9 100644
> > --- a/drivers/staging/gma500/psb_drv.c
> > +++ b/drivers/staging/gma500/psb_drv.c
> > @@ -228,7 +228,7 @@ static int psb_do_init(struct drm_device *dev)
> >  
> >  
> >  	spin_lock_init(&dev_priv->irqmask_lock);
> > -	mutex_init(&dev_priv->mutex_2d);
> > +	spin_lock_init(&dev_priv->lock_2d);
> >  
> >  	PSB_WSGX32(0x00000000, PSB_CR_BIF_BANK0);
> >  	PSB_WSGX32(0x00000000, PSB_CR_BIF_BANK1);
> > diff --git a/drivers/staging/gma500/psb_drv.h b/drivers/staging/gma500/psb_drv.h
> > index 9cbb494..11d963a 100644
> > --- a/drivers/staging/gma500/psb_drv.h
> > +++ b/drivers/staging/gma500/psb_drv.h
> > @@ -612,7 +612,7 @@ struct drm_psb_private {
> >  	void (*exit_idle)(struct drm_device *dev, u32 update_src);
> >  
> >  	/* 2D acceleration */
> > -	struct mutex mutex_2d;
> > +	spinlock_t lock_2d;
> >  
> >  	/* FIXME: Arrays anyone ? */
> >  	struct mdfld_dsi_encoder *encoder0;	
> > diff --git a/kernel/printk.c b/kernel/printk.c
> > index e861488..af2eec8 100644
> > --- a/kernel/printk.c
> > +++ b/kernel/printk.c
> > @@ -512,7 +512,7 @@ static void __call_console_drivers(unsigned start, unsigned end)
> >  	struct console *con;
> >  
> >  	for_each_console(con) {
> > -		if (exclusive_console && con != exclusive_console)
> > +		if (0 && exclusive_console && con != exclusive_console)
> >  			continue;
> >  		if ((con->flags & CON_ENABLED) && con->write &&
> >  				(cpu_online(smp_processor_id()) ||
> 
> Are you sure you want this in the tree?  I don't feel comfortable making
> this fix just for one staging driver right now, do you?

I've applied the other 8 patches here, skipping this one.

greg k-h
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