Messages in this thread | | | Subject | Re: [PATCH][RFC] tracing/context-tracking: Add preempt_schedule_context() for tracing | From | Steven Rostedt <> | Date | Fri, 31 May 2013 11:18:48 -0400 |
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On Fri, 2013-05-31 at 15:43 +0200, Frederic Weisbecker wrote:
> > +void __sched notrace preempt_schedule_context(void) > > +{ > > + struct thread_info *ti = current_thread_info(); > > + enum ctx_state prev_ctx; > > + > > + if (likely(ti->preempt_count || irqs_disabled())) > > + return; > > + > > + /* > > + * Need to disable preemption in case user_exit() is traced > > + * and the tracer calls preempt_enable_notrace() causing > > + * an infinite recursion. > > + */ > > + preempt_disable_notrace(); > > + prev_ctx = this_cpu_read(context_tracking.state); > > + user_exit(); > > You can reuse exception_enter()
I originally did use that, but then noticed that everything else in context_tracking.c used context_tracking.state directly. I have no problems doing it this way again.
> > > + preempt_enable_no_resched_notrace(); > > + > > + preempt_schedule(); > > + > > + preempt_disable_notrace(); > > + if (prev_ctx == IN_USER) > > + user_enter(); > > And then exception_exit() here. > > I guess this replaces your fix with schedule_preempt_user(). I liked > it because it seems that: > > if (need_resched()) { > user_exit(); > local_irq_enable(); > schedule(); > local_irq_enable(); > user_enter(); > } > > is a common pattern of arch user resume preemption that we can consolidate. > > But your new patch probably makes it more widely safe for the function tracer > for any function that can be called and traced in IN_USER mode. Not only user preemption. > Think about do_notify_resume() for example if it is called after syscall_trace_leave(). > > Independantly, schedule_preempt_user() is still interesting for consolidation.
And I think that patch is still valid from just a clean up point of view. It just didn't cover all the cases needed for tracing.
I'll rewrite the patch and send it out for another review.
Thanks!
-- Steve
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