Subject: Re: MSI interrupts and disable_irq

From: Manfred Spraul <[email-masked]>
Date: Tue, 02 Oct 2007 21:03:34 +0200

Ayaz Abdulla wrote:
> I am trying to track down a forcedeth driver issue described by bug 
> 9047 in bugzilla (2.6.23-rc7-git1 forcedeth w/ MCP55 oops under heavy 
> load). I added a patch to synchronize the timer handlers so that one 
> handler doesn't accidently enable the IRQ while another timer handler 
> is running (see attachment 'Add timer lock' in bug report) and for 
> other processing protection.
>
> However, the system still had an Oops. So I added a lock around the 
> nv_rx_process_optimized() and the Oops has not happened (see 
> attachment 'New patch for locking' in bug report). This would imply a 
> synchronization issue. However, the only callers of that function are 
> the IRQ handler and the timer handlers (in non-NAPI case). The timer 
> handlers  use disable_irq so that the IRQ handler does not contend 
> with them. It looks as if disable_irq is not working properly.
Either disable_irq() is not working properly or interrupts are nested, 
i.e. the irq handler is called again while running.
Which timer handler do you mean? I only see disable_irq() in the 
configuration paths (set mtu, change ring size, ...) and in the tx 
timeout case.
Neither one should happen during normal operation.

--
    Manfred