Re: irq_fpu_usable() is irreliable

From: Ingo Molnar
Date: Wed Nov 18 2015 - 01:55:21 EST



* Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:

> [...] Recently I've been tracking down a problem in which irq_fpu_usable()
> returns false, yet a stack trace shows the first function is the syscall entry
> point. [...]

Is this 'problem' a performance problem (code not being able to use the FPU
occasionally and hence sporadically performing poorly), or some sort of actual
stability/correctness problem?

Also, what CPU does the test system have, Intel or AMD? The FPU behavior can be
very different in the two cases.

Third, could you post such a problematic stack trace?

Thanks,

Ingo
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