Messages in this thread | | | Date | Sun, 09 Mar 2003 18:15:09 +0100 | From | Manfred Spraul <> | Subject | Re: [PATCH] Fast path context switch - microoptimize FPU reload |
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Andi wrote:
>We don't need the lock prefix to test our local thread flags state. >Unfortunately test_thread_flag currently always uses test_bit which >has a LOCK on SMP, but that's unnecessary. LOCK is costly on P4, >so it's a good idea to avoid it. > >
No, LOCK is required: the TIF_ flags word is also used for signal delivery - writing without lock could corrupt state.
What about moving TIF_USEDFPU from the thread_info into task_struct->flags? This flag word is only accessed by "current", no special atomicity requirements.
-- Manfred
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