linux-kernel - Re: Spinlock query

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Message-ID: <44F501B3.9070200@surriel.com>
Date:	Tue, 29 Aug 2006 23:10:43 -0400
From:	Rik van Riel <riel@...riel.com>
To:	Rick Brown <rick.brown.3@...il.com>
CC:	kernelnewbies@...linux.org, linux-kernel@...r.kernel.org
Subject: Re: Spinlock query

Rick Brown wrote:
> Hi,
> 
> In my driver (Process context), I have written the following code:
> 
> --------------------------------------------
> spin_lock(lock)
> ...
> //Critical section to manipulate driver data

... interrupt hits here
     interrupt handler tries to grab the spinlock, which is already taken
     *BOOM*

> spin_u lock(lock)
> ---------------------------------------------
> 
> I have written similar code in my interrupt handler (Interrupt
> context). The driver data is not accessed from anywhere else. Is my
> code safe from any potential concurrency issues? Is there a need to
> use spin_lock_irqsave()? In both the places?

You need to use spin_lock_irqsave() from process context.
 From the interrupt handler itself it doesn't hurt, but it
shouldn't matter much since interrupt handlers should not
get preempted.

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