Re: [PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler

[michael]

Hi
> On Wed, 30 Jan 2008 00:12:23 +0100
> michael <trimarchi@xxxxxxxxxxxxxxxx> wrote:
>
>   
> > - Voluntary Kernel Preemption the system (crash)
> > - Preemptible  Kernel (crash)
> >     
>
> Ouch. I'm assuming this is with DMA disabled?
>
>   
Yes, is with DMA disabled
> > /*
> >  * Drop the lock here since it might end up calling
> >  * uart_start(), which takes the lock.
> >    spin_unlock(&port->lock);
> >  */
> >     tty_flip_buffer_push(port->info->tty);
> > /*
> >     spin_lock(&port->lock);
> >  */
> > The same code with this comments out runs
> >     
>
> Now, _that_ is strange. I can't see anything that needs protection
> across that call; in fact, I think we can lock a lot less than what we
> currently do.
>
>   
I explain it bad:
- with spin_lock the system seems, there is no problem with Valuntary 
Preeption and
Preemptible Kernel
- with full preemption  it runs but the serial line can't be used for 
receiving at
high bit rate (using lrz)
> > Complete Preemption (Real-Time) ok but the serials is just unusable due
> > to too many overruns (just using lrz)
> >     
>
> Is it worse than before? IIRC Remy mentioned something about
> IRQF_NODELAY being the reason for moving all this code to softirq
> context in the first place; does the interrupt handler run in hardirq
> context?
>
>   
In the complete preemption yes.
> > The system is stable and doesn't crash reverting this patch.
> > I don't test with the thread hardirqs active.
> >     
>
> Ok.
>
>   
> > Is the kmalloc correct?
> > maybe:
> > data = kmalloc(ATMEL_SERIAL_RINGSIZE * sizeof(struct atmel_uart_char), 
> > GFP_KERNEL);
> >     
>
> I think you're right. Can you change it and see if it helps?
>
>   
I just change it because I have corruption on receiving buffer. All
my test are done with this fix
> I guess I didn't test it thoroughly enough with DMA
> disabled...slub_debug ought to catch such things, but not until we
> receive enough data to actually overflow the buffer.
>
>   
I just test it I don't have
buffer overflow.

I protect with a spinlock the access to the register when we sending
from the tasklet. It is correct?
> Why should it be? If it should, we must move the call to tasklet_init
> into atmel_startup too, and I don't really see the point.
>
>   
Ok


Regards Michael
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