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Re: do_IRQ query

To: Ranjan Parthasarathy <ranjanp@efi.com>
Subject: Re: do_IRQ query
From: Jun Sun <jsun@mvista.com>
Date: Thu, 12 Jun 2003 14:12:41 -0700
Cc: linux-mips@linux-mips.org, jsun@mvista.com
In-reply-to: <D9F6B9DABA4CAE4B92850252C52383AB07968330@ex-eng-corp.efi.com>; from ranjanp@efi.com on Thu, Jun 12, 2003 at 01:16:51PM -0700
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <D9F6B9DABA4CAE4B92850252C52383AB07968330@ex-eng-corp.efi.com>
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On Thu, Jun 12, 2003 at 01:16:51PM -0700, Ranjan Parthasarathy wrote:
> Is it safe to call do_IRQ directly inside interrupt handlers without doing a 
> irq_enter. I have seen ksoftirqd_CPUX crashes when I call the do_IRQ routines 
> directly instead of the following sequence.
> 
> irq_enter()
> do_IRQ
> irq_exit()
>

This is not right.  irq_enter()/irq_exit() is already called in 
handle_IRQ_event(), which in turn is called by do_IRQ().  YOu 
don't need this yourself.  

The rest of do_IRQ() code is protected by closing interrupts.

Something must be wrong in your system.  If you show the crash message,
we might be able to tell more.

> Some code use it while some do not. The timer code in arch/mips/kernel/time.c 
> uses it in ll_timer_interrupt. Some ports call this function directly in 
> their interrupt handlers.

Those ll_timer_xxx functions are alternative routes (fast ones) to
do_IRQ(), and therefore it needs to protect itself by calling
irq_enter()/irq_exit().

Jun

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