Re: [SMP lock BUG?] Re: Feedback on preemptible kernel patch

From: Manfred Spraul (manfred@colorfullife.com)
Date: Sat Sep 08 2001 - 18:11:05 EST


> This is interesting. [Assumes UP Athlon - correct]
> Note that all BUGs out in highmem.h:95 (kmap_atomic)
> and that test is only on if you have enabled HIGHMEM_DEBUG
> [my analyze is done with a 2.4.10-pre2 kernel, but I checked with
> later patches and I do not think they fix it either...]
>
> The preemptive kernel puts more SMP stress on the kernel than
> running with multiple CPUs.
>
> So this might be a potential bug in the kernel proper, running with
> a SMP computer.

No.
It seems to be a missing ctx_sw_off() in highmem.h:
kmap_atomic uses a per-cpu variable, thus ctx_sw_off() is needed in
kmap_atomic, and ctx_sw_on() in kunmap_atomic().

--
    Manfred

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/



This archive was generated by hypermail 2b29 : Sat Sep 15 2001 - 21:00:16 EST