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authorPeter Zijlstra <peterz@infradead.org>2020-11-16 13:10:12 +0100
committerPaul E. McKenney <paulmck@kernel.org>2020-11-19 19:34:17 -0800
commit6dbce04d8417ae706596366e16841d77c454ba52 (patch)
treef4f34a632bbf504557cb50c2412d80225f8b0576 /kernel/rcu
parentc583bcb8f5edd48c1798798e341f78afb9bf4f6f (diff)
rcu: Allow rcu_irq_enter_check_tick() from NMI
Eugenio managed to tickle #PF from NMI context which resulted in hitting a WARN in RCU through irqentry_enter() -> __rcu_irq_enter_check_tick(). However, this situation is perfectly sane and does not warrant an WARN. The #PF will (necessarily) be atomic and not require messing with the tick state, so early return is correct. This commit therefore removes the WARN. Fixes: aaf2bc50df1f ("rcu: Abstract out rcu_irq_enter_check_tick() from rcu_nmi_enter()") Reported-by: "Eugenio PĂ©rez" <eupm90@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 06895ef85d69..93e1808ac3fc 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -928,8 +928,8 @@ void __rcu_irq_enter_check_tick(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- // Enabling the tick is unsafe in NMI handlers.
- if (WARN_ON_ONCE(in_nmi()))
+ // If we're here from NMI there's nothing to do.
+ if (in_nmi())
return;
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),