Re: [PATCH 2/3] work_on_cpu: Use our own workqueue.
From: Andrew Morton
Date: Tue Feb 03 2009 - 22:01:38 EST
On Wed, 4 Feb 2009 13:14:31 +1030 Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
> On Tuesday 03 February 2009 14:36:49 Andrew Morton wrote:
> > But as you say, rdmsr_on_cpu() is easy to do, using
> > smp_call_function_single(). Then we can easily convert all other
> > work_on_cpu() callers to smp_call_function_single() and zap
> > work_on_cpu(). The best outcome, methinks.
>
> grepping for set_cpus_allowed reveals the following users in the
> first third (when I got tired of it):
>
> File Function Context Calls
> powerpc/kernel/smp.c smp_cpus_done kernel_init smp_ops->setup_cpu()
> x86/.../speedstep-ich.c _speedstep_get cpufreq speedstep_get_processor_frequency()
> x86/.../powernow-k8.c check_supported_cpu cpufreq cpuid_*()
> x86/.../powernow-k8.c powernowk8_target cpufreq mutex_lock, etc
> x86/.../powernow-k8.c powernowk8_cpu_init boot/hotplg rdmsr,wrmsr
> x86/.../powernow-k8.c powernowk8_get cpufreq rdmsr
> x86/.../speedstep-centrino.c get_cur_freq cpufreq rdmsr
> x86/.../speedstep-centrino.c centrino_target cpufreq rdmsr,wrmsr
> x86/kernel/reboot.c nativ..._shutdown sys_reboot misc
> x86/.../microcode_core.c do_microcode_update sys_write microcode_ops->request_microcode_user
> x86/.../microcode_core.c reload_store sys_write mutex_lock, etc
>
> Some of these (reboot) we don't care what they do to cpumask. Some are
> poor style, but not critical (boot time). Some can use smp_call_function.
>
> But there are some which should *not* be frobbing their cpus_allowed, and
> really do seem to want a user context.
>
> I think you're right though: smp_call_function_single (or neat wrappers)
> where possible, work_on_cpu which can fail for the others, and we'll just
> have to plumb in the error returns.
I bet a lot of those can use plain old schedule_work_on().
Could it be that after converting things to
smp_call_function_single()/schedule_work_on(), we don't need
work_on_cpu()?
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