"Paul E. McKenney" <paul...@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 <t...@linutronix.de> >> Cc: "Paul E. McKenney" <paul...@kernel.org> >> Cc: Joel Fernandes <j...@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 :)
