Messages in this thread | | | Date | Tue, 27 Oct 2020 11:09:49 +0100 | From | Thomas Gleixner <> | Subject | [patch 0/2] x86/fpu: Make fpu_lock() RT compliant |
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FPU serialization uses
preempt_disable(); local_bh_disable();
which is silly because local_bh_disable() implicitly disables preemption. So this can be reduced to local_bh_disable().
But this does not work on RT kernels because local_bh_disable() only serializes bottom half related processing via a local lock, but does not disable preemption.
On RT kernels preempt_disable() is the right choice because on RT bottom half processing is always in thread context, so preempt_disable() implicitly protects against bottom half processing there.
Thanks,
tglx
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