Messages in this thread | | | Date | Tue, 5 May 2020 15:24:29 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [patch V4 part 3 11/29] rcu: Provide rcu_irq_exit_preempt() |
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On Wed, May 06, 2020 at 12:05:04AM +0200, Thomas Gleixner wrote: > "Paul E. McKenney" <paulmck@kernel.org> writes: > > > On Tue, May 05, 2020 at 03:44:05PM +0200, Thomas Gleixner wrote: > >> Interrupts and exceptions invoke rcu_irq_enter() on entry and need to > >> invoke rcu_irq_exit() before they either return to the interrupted code or > >> invoke the scheduler due to preemption. > >> > >> The general assumption is that RCU idle code has to have preemption > >> disabled so that a return from interrupt cannot schedule. So the return > >> from interrupt code invokes rcu_irq_exit() and preempt_schedule_irq(). > >> > >> If there is any imbalance in the rcu_irq/nmi* invocations or RCU idle code > >> had preemption enabled then this goes unnoticed until the CPU goes idle or > >> some other RCU check is executed. > >> > >> Provide rcu_irq_exit_preempt() which can be invoked from the > >> interrupt/exception return code in case that preemption is enabled. It > >> invokes rcu_irq_exit() and contains a few sanity checks in case that > >> CONFIG_PROVE_RCU is enabled to catch such issues directly. > >> > >> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > >> Cc: "Paul E. McKenney" <paulmck@kernel.org> > >> Cc: Joel Fernandes <joel@joelfernandes.org> > > > > The ->dynticks_nmi_nesting field is going away at some point, but > > there is always "git merge". ;-) > > Yes. The logistics for merging all of this is going to be interesting :)
;-) ;-) ;-)
Thanx, Paul
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