Messages in this thread | | | Subject | Re: [PATCH v2 1/7] entry: add arch_in_rcu_eqs() | From | Nicolas Saenz Julienne <> | Date | Fri, 21 Jan 2022 18:34:55 +0100 |
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On Wed, 2022-01-19 at 10:58 +0000, Mark Rutland wrote: > All architectures have an interruptible RCU extended quiescent state > (EQS) as part of their idle sequences, where interrupts can occur > without RCU watching. Entry code must account for this and wake RCU as > necessary; the common entry code deals with this in irqentry_enter() by > treating any interrupt from an idle thread as potentially having > occurred with an EQS and waking RCU for the duration of the interrupt > via rcu_irq_enter() .. rcu_irq_exit(). > > Some architectures may have other interruptible EQSs which require > similar treatment. For example, on s390 is it necessary to enable > interrupts around guest entry in the middle of a period where core KVM > code has entered an EQS. > > So that architectueres can wake RCU in these cases, this patch adds a > new arch_in_rcu_eqs() hook to the common entry code which is checked in > addition to the existing is_idle_thread() check, with RCU woken if > either returns true. A default implementation is provided which always > returns false, which suffices for most architectures. > > As no architectures currently implement arch_in_rcu_eqs(), there should > be no functional change as a result of this patch alone. A subsequent > patch will add an s390 implementation to fix a latent bug with missing > RCU wakeups. > > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: Christian Borntraeger <borntraeger@linux.ibm.com> > Cc: Heiko Carstens <hca@linux.ibm.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Paul E. McKenney <paulmck@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Sven Schnelle <svens@linux.ibm.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > ---
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Thanks,
-- Nicolás Sáenz
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