Messages in this thread | | | Date | Tue, 3 Sep 2013 11:44:54 -0400 | From | Steven Rostedt <> | Subject | Re: [gcv v3 06/35] scheduler: Replace __get_cpu_var uses |
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On Tue, 3 Sep 2013 16:45:45 +0200 Frederic Weisbecker <fweisbec@gmail.com> wrote:
> 2013/9/3 Christoph Lameter <cl@linux.com>: > > On Thu, 29 Aug 2013, Steven Rostedt wrote: > > > >> How many places use the this_cpu_*() without preemption disabled? I > >> wouldn't think there's many. I never complained about another variant, > >> so you need to ask those that have. The tough question for me is what > >> that variant name should be ;-) > > > > Tried to add preemption checks but the basic issue is that many of the > > checks themselves use this_cpu_ops. percpu.h is very basic to the > > operation of fundamental primitives for preempt etc. Use of a BUG_ON needs > > a seris of includes in percpu.h that cause more trouble. > > > > If I switch __this_cpu ops to check for preemption then the logic for > > preemption etc must use the raw_this_cpu ops. > > IIUC the issue is that preempt debug checks themselves use per cpu > operations that can result in preempt debug checks? Hence a recursion. > Do you have an example of that? > > Also in this case this must be fixed anyway given the checks that > already exist in smp_processor_id(), __get_cpu_var(), ...
Right, that's why there's a raw_smp_processor_id() and __raw_get_cpu_var(). Those two are the ones without checks, and they are called by the non "raw" versions after the check is done.
Really, what's so damn hard about this?
-- Steve
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