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Date: Wed, 25 Apr 2007 18:33:49 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: pwarudkar@aol.com
Cc: Jiri Kosina <jikos@jikos.cz>, dsk6@pitt.edu, linux-kernel@vger.kernel.org
Subject: Re: Sleep during spinlock in TPM driver
Message-Id: <20070425183349.c3f661f4.akpm@linux-foundation.org>
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On Mon, 23 Apr 2007 08:14:03 -0400 (EDT) Parag Warudkar <pwarudkar@aol.com> wrote:

> --- linux-2.6-us/drivers/char/tpm/tpm.c	2007-04-21 14:55:03.134975360 -0400
> +++ linux-2.6-wk/drivers/char/tpm/tpm.c	2007-04-22 14:58:51.957999963 -0400
> @@ -942,12 +942,12 @@
>  {
>  	struct tpm_chip *chip = file->private_data;
>  
> +	flush_scheduled_work();
>  	spin_lock(&driver_lock);
>  	file->private_data = NULL;
> -	chip->num_opens--;
>  	del_singleshot_timer_sync(&chip->user_read_timer);
> -	flush_scheduled_work();
>  	atomic_set(&chip->data_pending, 0);

btw, this driver has a timer handler which does:

static void user_reader_timeout(unsigned long ptr)
{
        struct tpm_chip *chip = (struct tpm_chip *) ptr;

        schedule_work(&chip->work);
}

which appears to duplicate schedule_delayed_work()'s functionality.