Re: mmotm 2009-04-10-02-21 uploaded - forkbombed by work_for_cpu

From: Linus Torvalds
Date: Mon Apr 13 2009 - 19:57:59 EST




So I applied this (commit 01599fca6758d2cd133e78f87426fc851c9ea725:
"cpufreq: use smp_call_function_[single|many]() in acpi-cpufreq.c"), but
just realized - because of a compiler warning - that this looks
suspicious:

On Mon, 13 Apr 2009, Andrew Morton wrote:
> @@ -283,7 +280,7 @@ static unsigned int get_measured_perf(st
> unsigned int perf_percent;
> unsigned int retval;
>
> - if (!work_on_cpu(cpu, read_measured_perf_ctrs, &readin))
> + if (smp_call_function_single(cpu, read_measured_perf_ctrs, &cur, 1))
> return 0;
>
> cur.aperf.whole = readin.aperf.whole -

How and why did that "read_measured_perf_ctrs, &readin" become
"read_measured_perf_ctrs, &cur" when the work_on_cpu() was converted to
"smp_call_function_single()"?

Looks like a bug. But such an odd one that I wonder whether there was some
thought behind it? Andrew?

Linus


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