On Thu, Oct 05, 2017 at 11:55:39AM -0400, Steven Rostedt wrote: > On Thu, 5 Oct 2017 10:37:59 -0500 > Julia Cartwright <ju...@ni.com> wrote: > > > On Thu, Oct 05, 2017 at 05:27:30PM +0200, Thomas Gleixner wrote: > > > On Thu, 5 Oct 2017, Julia Cartwright wrote: > > > > On Tue, Oct 03, 2017 at 12:49:19PM -0300, Arnaldo Carvalho de Melo > > > > wrote: > > > > > - preempt_disable(); > > > > > + preempt_disable_nort(); > > > > > this_cpu_inc(*sc->buffers_allocated); > > > > > > > > Have you tried this on RT w/ CONFIG_DEBUG_PREEMPT? I believe that the > > > > this_cpu_* operations perform a preemption check, which we'd trip. > > > > > > Good point. Changing this to migrate_disable() would do the trick. > > > > Wouldn't we still trip the preempt check even with migration disabled? > > In another thread I asked the same question: should the preemption > > checks here be converted to migration-checks in RT? > > Is it a "preemption check"?
Sorry if I was unclear, more precisely: the this_cpu_* family of accessors, w/ CONFIG_DEBUG_PREEMPT currently spits out a warning when the caller is invoked in a context where preemption is enabled. The check is shared w/ the smp_processor_id() check, as implemented in lib/smp_processor_id.c. It effectively boils down to a check of preempt_count() and irqs_disabled(). > Getting a cpu # should only care about migration. I think we're agreeing? :) > This isn't the same as a rcu_sched check is it? That does care about > preemption. This is something totally different, I think. Julia
