[Xen-devel] schedulers' use of cpumask_scratch

["Jan Beulich" <JBeulich@xxxxxxxx>]

Dario,

analyzing a stack overflow I've run into the other day I came across
credit1's __runq_tickle() not only itself having two cpumask_t
variables on the stack, but then also calling cpumask_raise_softirq()
(which uses yet one more). I then recalled you have a scratch mask
in the scheduler, and I did look at where it's used. While it's already
in use in credit1's __runq_tickle(), I then got puzzled by the different
ways credit1 and credit2 use the variable: The former always uses
scratch_cpumask_cpu() with the subject CPU as argument, while
the latter always uses plain scratch_cpumask. What guarantees
that these two uses never conflict, if both schedulers are active for
some part of the system?

Thanks, Jan


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