|| ||Linus Torvalds <torvalds-AT-linux-foundation.org> |
|| ||Rusty Russell <rusty-AT-rustcorp.com.au> |
|| ||Re: Fix quilt merge error in acpi-cpufreq.c |
|| ||Wed, 15 Apr 2009 08:28:45 -0700 (PDT)|
|| ||Ingo Molnar <mingo-AT-elte.hu>,
Linux Kernel Mailing List <linux-kernel-AT-vger.kernel.org>,
Andrew Morton <akpm-AT-linux-foundation.org>,
Dave Jones <davej-AT-redhat.com>|
|| ||Article, Thread
On Wed, 15 Apr 2009, Rusty Russell wrote:
> The API is screwy. It excludes the current CPU from the mask,
> unconditionally. It's a tlb flush helper masquerading as a general function.
> (smp_call_function has the same issue).
> Something like this?
> Subject: smp_call_function_many: add explicit exclude_self flag
No. This just makes the API even screwier. It fixes the
"smp_processor_id()" thing, but it is
(a) horribly buggy
See the 'return' without any put_cpu()
(b) horribly buggy
if (exclude_self && cpu == this_cpu)
cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
things are wrong - we need to do that "jump over our own CPU" thing
regardless of whether 'exclude_self' is set or not, since we're going
to special-case our own CPU anyway.
(c) Wrong, even if it wasn't (horribly buggy)^2
Adding "flags" to an interface doesn't make it better. Quite the
reverse. It makes it worse. It also makes it even MORE different from
all the other smp_call_function's, which just do the 'self' cpu
without any stupid conditionals and flags.
IOW, it would make things worse even if it worked. Which it doesn't.
> Impact: clarify and extend confusing API
And what the hell is up with these bogus "Impact:" things? Who started
doing that, and why? If your single-line explanation at the top is not
good enough, and your multi-line explanation isn't clear enough, then you
should fix the OTHER parts, not add that _idiotic_ "Impact" statement.
The thing has spread like wildfire, and it's STUPID.
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