Re: [Xen-devel] [PATCH v5 2/2] x86: add accessors for scratch cpu mask

[Jan Beulich <jbeulich@xxxxxxxx>]

On 11.03.2020 16:34, Roger Pau Monné wrote:
> On Fri, Feb 28, 2020 at 01:42:58PM +0100, Jan Beulich wrote:
>> On 28.02.2020 13:07, Roger Pau Monne wrote:
>>> Current usage of the per-CPU scratch cpumask is dangerous since
>>> there's no way to figure out if the mask is already being used except
>>> for manual code inspection of all the callers and possible call paths.
>>>
>>> This is unsafe and not reliable, so introduce a minimal get/put
>>> infrastructure to prevent nested usage of the scratch mask and usage
>>> in interrupt context.
>>>
>>> Move the declaration of scratch_cpumask to smp.c in order to place the
>>> declaration and the accessors as close as possible.
>>>
>>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>>
>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Ping? This seems to have the required RB, but hasn't been committed.

While as per the R-b this technically is fine, I continue to be
uncertain whether we actually want to go this far. Andrew, as
per a discussion we had when I was pondering whether to commit
this, also looks to have similar concerns (which iirc he said he
had voiced on irc).

Jan

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