Re: [Bugme-new] [Bug 33502] New: Caught 64-bit read from uninitialized memory in __alloc_skb

Christoph Lameter
2011-05-10T20:33:35Z

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On Tue, 10 May 2011, Eric Dumazet wrote:

> Le mardi 10 mai 2011 à 14:38 -0500, Christoph Lameter a écrit :
>
> > Optimizing? You think about this as concurrency issue between multiple
> > cpus. That is fundamentally wrong. This is dealing with access to per cpu
> > data and the concurrency issues are only with code running on the *same*
> > cpu.
> >
>
> If you enable irqs, then this object can be allocated by _this_ cpu and
> given to another one.

That will cause an incrementing of the tid.

> Another cpu can free the page, forcing you to call a very expensive
> function, that might give obsolete result as soon it returns.

No the other cpu cannot free the page since the page is pinned by
the current cpu (see PageFrozen()).

> Maybe I am just tired tonight, this seems very obvious, I must miss
> something.

Yeah you are way off thinking about cpu to cpu concurrency issues that do
not apply here.