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Subject: Re: A general question on SMP-safe driver code.
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Jim Nelson <james4765@verizon.net>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Sat, 25 Dec 2004 12:23:24 +0000
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On Gwe, 2004-12-24 at 22:58, Jim Nelson wrote:
> Looking at a few older drivers, I'm trying to figure out the best ways to handle 
> some locking.  Using drivers/char/esp.c as an example (since it's the one I'm 
> trying to grok right now), here is one example:

> ;
> 	serial_out(info, UART_ESI_CMD1, ESI_GET_TX_AVAIL);
> 	spin_unlock_irq(&info->esp_lock);
> 
> 	while ((serial_in(info, UART_ESI_STAT1) != 0x03) ||
> 		(serial_in(info, UART_ESI_STAT2) != 0xff)) {

You need to guard these as well in the locks. It might actually look a
lot cleaner to have functions esp_send_command(info, a, b) and the like
which do the locking internally ?