Re: [PATCH] cpumask: alloc blank cpumask left over
From: Avi Kivity
Date: Sat Jun 06 2009 - 05:24:21 EST
Rusty Russell wrote:
On Fri, 5 Jun 2009 03:26:57 pm Yinghai Lu wrote:
Rusty Russell wrote:
On Fri, 5 Jun 2009 06:31:31 am Yinghai Lu wrote:
avoid suprise when MAXSMP is enabled
Signed-off-by: Yinghai Lu <yinghai.lu@xxxxxxxxxx>
I understand the temptation, but two questions arise:
1) Shouldn't we actually audit to see if any of these are currently
problems,
those are defined as static cpumask_var_t, and if MAXSMP is not used, they
are cleared already
OK, here's what I've got in my tree. Ingo, I think this should go in the
current -rc to avoid nasty bugs.
BTW, the original alloc_cpumask_var did zero; that was dropped after arguments
over efficiency and fitting with other interfaces, but I clearly had the old
semantics in my head for a while.
Using __GFP_ZERO is equivalent to using memset() instead of
cpumask_clear(). It's better to call cpumask_clear() or provide an API
to alloc+clear.
Further, what about the non-MAXSMP case:
static inline bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
{
return true;
}
We explicity clear on MAXSMP and rely on static initialization for the
non-MAXSMP, laying a neat trap for anyone who makes the variable
non-static. Let's be less subtle that that.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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