Messages in this thread | | | Date | Mon, 27 Aug 2007 22:09:46 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH] fix bogus hotplug cpu warning |
| |
On Mon, 27 Aug 2007, Andrew Morton wrote: > On Mon, 27 Aug 2007 21:37:14 +0100 (BST) > Hugh Dickins <hugh@veritas.com> wrote: > > > > So I agree with the patch, but not with its description. > > > > I don't see which part of the description you disagree with, but please > > do improve it if you can. > > I'd change the description to > > > current_is_keventd() is a stupid load of crap. It does > > int current_is_keventd(void) > { > struct cpu_workqueue_struct *cwq; > int cpu = smp_processor_id(); /* preempt-safe: keventd is per-cpu */ > > but that comment (and the code itself) only make sense when > current_is_keventd() is called by keventd. In which case thers is no point > in the function even existing!
I disagree. The comment (your very own, I think?) and the code made sense to me. It's saying this is rather unusual, but safe against preemption, because keventd is per-cpu (it might perhaps be better if it said each keventd is bound to a cpu).
The code works in such a way that if it is a keventd, then it'll correctly arrive at the answer yes; and if it's not a keventd, then even if it's preempted to a different cpu in the middle, the test won't match any keventd and so it'll correctly arrive at the answer no.
But I'm content with the half-liner already there.
> > We need to use raw_smp_processor_id() so that non-keventd (or, more > specifically, non-pinned-to-one-cpu) callers won't generate "using > smp_processor_id() in preemptible" warnings.
Yes, that's true, raw_smp_processor_id() is needed to avoid the warning; but it was already preempt-safe with smp_processor_id(), just in danger of giving an inappropriate warning.
Hugh - 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/
| |