Re: [PATCH] 2.6.18-rt7: PowerPC: fix breakage in threaded fasteoi type IRQ handlers

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Benjamin Herrenschmidt wrote:

> > > As fasteoi type chips never had to define their ack() method before the
> > > recent Ingo's change to handle_fasteoi_irq(), any attempt to execute handler
> > > in thread resulted in the kernel crash. So, define their ack() methods to be
> > > the same as their eoi() ones...

> > > Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>

> > > ---
> > > Since there was no feedback on three solutions I suggested, I'm going the way
> > > of least resistance and making the fasteoi type chips behave the way that
> > > handle_fasteoi_irq() is expecting from them...

> > Wait wait wait .... Can somebody (Ingo ?) explain me why the fasteoi
> > handler is being changed and what is the rationale for adding an ack
> > that was not necessary before ?

   It's changed in the RT patch for the case of threaded IRQ. This patch is 
not for the mainline kernels.

> To be more precise, I don't see in what circumstances a fasteoi type PIC
> would need an ack routine that does something different than the eoi...
> and if it always does the same thing, why not just call eoi ?

   Because Ingo decided that calling mask() and ack() methods was a better 
than calling mask() and eoi(). Here's the thread:

http://ozlabs.org/pipermail/linuxppc-dev/2006-October/026546.html

> Ben.

WBR, Sergei

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/