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From: Haavard Skinnemoen <hskinnemoen@atmel.com>
To: michael <trimarchi@gandalf.sssup.it>
Cc: Remy Bohmer <linux@bohmer.net>,
	fabio@gandalf.sssup.it, Andrew Victor <linux@maxim.org.za>,
	Chip Coldwell <coldwell@redhat.com>,
	Marc Pignat <marc.pignat@hevs.ch>,
	David Brownell <david-b@pacbell.net>,
	linux-kernel@vger.kernel.org, Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler
Date: Wed, 30 Jan 2008 10:41:13 +0100	[thread overview]
Message-ID: <20080130104113.48ec376f@dhcp-252-066.norway.atmel.com> (raw)
In-Reply-To: <479FB2D7.4020804@gandalf.sssup.it>

On Wed, 30 Jan 2008 00:12:23 +0100
michael <trimarchi@gandalf.sssup.it> wrote:

> I'm testing this patch on an at91sam9260 on 2.6.24-rt. I'm using this
> patch with the tclib support for hrtimer and the clocksource pit_clk.
> These are the results:
> 
> - Voluntary Kernel Preemption the system (crash)
> - Preemptible  Kernel (crash)

Ouch. I'm assuming this 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.

> 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?

> The system is stable and doesn't crash reverting this patch.
> I don't test with the thread hardirqs active.

Ok.

> >> +	ret = -ENOMEM;
> >> +	data = kmalloc(ATMEL_SERIAL_RINGSIZE, GFP_KERNEL);
> >> +	if (!data)
> >> +		goto err_alloc_ring;
> >> +	port->rx_ring.buf = data;
> >> +
> >>  	ret = uart_add_one_port(&atmel_uart, &port->uart);
> >>     
> 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 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.

> >> @@ -1033,6 +1165,9 @@ static int __devexit atmel_serial_remove(struct platform_device *pdev)
> >>  
> >>  	ret = uart_remove_one_port(&atmel_uart, port);
> >>  
> >> +	tasklet_kill(&atmel_port->tasklet);
> >> +	kfree(atmel_port->rx_ring.buf);
> >> +
> >>     
> Why the tasklet_kill is not done in atmel_shutdown?

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.

Haavard

  reply	other threads:[~2008-01-30  9:41 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20080129224316.GA23155@gandalf.sssup.it>
2008-01-29 23:12 ` michael
2008-01-30  9:41   ` Haavard Skinnemoen [this message]
2008-01-30 10:21     ` Remy Bohmer
2008-01-30 10:34       ` Haavard Skinnemoen
2008-01-30 11:05         ` Remy Bohmer
2008-01-30 12:43           ` Haavard Skinnemoen
2008-01-30 15:25           ` michael
2008-01-30 10:29     ` michael
2008-01-30 12:36       ` Haavard Skinnemoen
2008-01-30 15:26         ` michael
2008-01-30 15:46           ` Haavard Skinnemoen
2008-01-31  1:53             ` michael
2008-01-31 15:07               ` Haavard Skinnemoen
2008-01-31 19:36                 ` Remy Bohmer
2008-02-04 12:39                   ` Haavard Skinnemoen
2008-02-04 19:44                     ` Remy Bohmer
2008-02-06 12:19                       ` michael
2008-02-06 19:41                         ` Remy Bohmer
2008-02-13 11:07                           ` michael
2008-02-13 20:13                             ` Remy Bohmer
2008-02-14  7:30                               ` michael
2008-02-04 19:01                 ` michael
2008-02-04 20:25                   ` Haavard Skinnemoen
2008-02-05 12:29                     ` michael
2008-02-06 12:30                       ` Haavard Skinnemoen
2008-02-06 13:41                         ` michael
2008-02-06 15:22                           ` Haavard Skinnemoen
2008-01-24 12:41 [PATCH -mm v4 0/9] atmel_serial cleanups and improvements Haavard Skinnemoen
2008-01-24 12:41 ` [PATCH -mm v4 1/9] MAINTAINERS: Add myself as maintainer of the atmel_serial driver Haavard Skinnemoen
2008-01-24 12:41   ` [PATCH -mm v4 2/9] atmel_serial: Clean up the code Haavard Skinnemoen
2008-01-24 12:41     ` [PATCH -mm v4 3/9] atmel_serial: Use cpu_relax() when busy-waiting Haavard Skinnemoen
2008-01-24 12:41       ` [PATCH -mm v4 4/9] atmel_serial: Use existing console options only if BRG is running Haavard Skinnemoen
2008-01-24 12:41         ` [PATCH -mm v4 5/9] atmel_serial: Fix bugs in probe() error path and remove() Haavard Skinnemoen
2008-01-24 12:41           ` [PATCH -mm v4 6/9] atmel_serial: Split the interrupt handler Haavard Skinnemoen

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