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SubjectRe: [CFT][RFC] HT scheduler

Rusty Russell wrote:

>In message <> you write:
>>+ * See comment for set_cpus_allowed. calling rules are different:
>>+ * the task's runqueue lock must be held, and __set_cpus_allowed
>>+ * will return with the runqueue unlocked.
>Please, never *ever* do this.
>Locking is probably the hardest thing to get right, and code like this
>makes it harder.

Although in this case it is only one lock, and its only used in
one place, with comments. But yeah its far more complex than a
blocking semaphore would be.

>Fortunately, there is a simple solution coming with the hotplug CPU
>code: we need to hold the cpucontrol semaphore here anyway, against
>cpus vanishing.
>Perhaps we should just use that in both places.

We could just use a private semaphore until the hotplug code is in place.

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