linux-kernel - Re: [PATCH 1/1] cpumask: smp_call_function

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Message-Id: <200811202138.05232.rusty@rustcorp.com.au>
Date:	Thu, 20 Nov 2008 21:38:04 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	linux-kernel@...r.kernel.org, Mike Travis <travis@....com>,
	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>,
	schwidefsky@...ibm.com, heiko.carstens@...ibm.com, npiggin@...e.de,
	axboe@...nel.dk
Subject: Re: [PATCH 1/1] cpumask: smp_call_function_many()

On Thursday 20 November 2008 17:27:07 Nick Piggin wrote:
> On Thursday 20 November 2008 15:44, Rusty Russell wrote:
> > I can prepare a separate patch which just changes this over, rather than
> > doing it as part of the smp_call_function_many() conversion, but I
> > couldn't stomach touching that quiescing code :(
>
> What's wrong with it? It's well commented and I would have thought pretty
> simple. A bit ugly, but straightforward. I still don't really see why it
> needs changing.

Ah, sorry if I was unclear.  The point of this 150+ patch series is to get 
cpumasks off the stack.

Here's the problem:

struct call_function_data {
	struct call_single_data csd;
	spinlock_t lock;
	unsigned int refs;
	cpumask_t cpumask;
	struct rcu_head rcu_head;
};
...

static void smp_call_function_mask_quiesce_stack(cpumask_t mask)
{
	struct call_single_data data;
...

So, it's far simpler just to fix the code to do the "dumb" thing.

Rusty.
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