Messages in this thread | | | Date | Wed, 23 Feb 2011 11:34:32 -0600 (CST) | From | Christoph Lameter <> | Subject | Re: [PATCH RFC tip/core/rcu 11/11] rcu: move TREE_RCU from softirq to kthread |
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On Wed, 23 Feb 2011, Mathieu Desnoyers wrote:
> > > > + > > > > + local_irq_save(flags); > > > > + cpu = smp_processor_id();
Drop this line.
> > > > + if (per_cpu(rcu_cpu_kthread_task, cpu) == NULL) {
use this_cpu_read(rcu_cpu_kthread_task)
> > > > + local_irq_restore(flags); > > > > + return; > > > > + } > > > > + per_cpu(rcu_cpu_has_work, cpu) = 1;
this_cpu_write(rcu_cpu_has_work, 1);
> This is not quite true on x86_64 and s390 anymore. __get_cpu_var() now > uses a segment selector override to get the local CPU variable on x86. > See x86's percpu.h for details.
__get_cpu_var cannot use a segment override since there are places where the address of the variable is taken. One needs to use this_cpu_ops for that.
> > True, but we could also argue that the multiple checks for being preempt > > can also be an issue. > > At least on x86 preemption don't actually need to be disabled: selection > of the right per-cpu memory location is done atomically with the rest of > the instruction by the segment selector.
Right.
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