Messages in this thread | | | Date | Thu, 7 Jun 2007 23:29:55 +0530 | From | "Satyam Sharma" <> | Subject | Re: [PATCH] Make smp_call_function{_single} go WARNING and return -EINVAL on !SMP (was Re: [PATCH] i386/x86_64: NMI watchdog: Protect smp_call_function() within CONFIG_SMP) |
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On 6/7/07, Heiko Carstens <heiko.carstens@de.ibm.com> wrote: > > The smp_call_function{_single} functions are used to run > > given function on all {or speicified} *other* CPUs. For > > UP systems, "other" CPUs simply don't exist, so we flag > > such incorrect usage of these functions using a WARNING. > > If other cpus don't exist then smp_call_function() should just do > *nothing* (there is no other cpu right?). We don't want to sprinkle > a ton of #ifdef CONFIG_SMP around each smp_call_function().
Yes, I suspected that, as mentioned on the other thread (ugh).
> > Also, -EBUSY is generally returned by arch implementations > > when they find that target_cpu == current_cpu, which is not > > a comparable case to the !SMP case. Use -EINVAL instead, > > similar to what powerpc does for !cpu_online(target), which > > is somewhat more analogous. > > No. Current semantics of smp_call_function_single() are that it > returns -EBUSY if called on the *current* cpu. Since on !CONFIG_SMP the > only possible cpu it can be called on is the current one, the only > sane return value is -EBUSY.
The inherent assumption that on !SMP the only possible CPU it can be called on is current (== 0) is precisely what I would want to be asserted formally in the code over here. If so, then return -EBUSY, else -EINVAL? - 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/
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