From 6136d6e48a0138f6be5bb3427dbeb0ba07a546a4 Mon Sep 17 00:00:00 2001 From: Paul E. McKenney Date: Tue, 3 Oct 2017 08:28:04 -0700 Subject: rcu: Clamp ->dynticks_nmi_nesting at eqs entry/exit In preparation for merging dyntick-idle irq handling into the NMI algorithm, clamp ->dynticks_nmi_nesting value to allow for interrupts that enter but never leave and vice versa. It is important that the clamping happen outside of the extended quiescent state. Otherwise, there will be short windows where irqs and NMIs fail to convince RCU to start watching. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcu.h | 2 ++ kernel/rcu/tree.c | 2 ++ 2 files changed, 4 insertions(+) (limited to 'kernel/rcu') diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 59c471de342a..f4a411964c41 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -56,6 +56,8 @@ #define DYNTICK_TASK_EXIT_IDLE (DYNTICK_TASK_NEST_VALUE + \ DYNTICK_TASK_FLAG) +#define DYNTICK_IRQ_NONIDLE ((INT_MAX / 2) + 1) + /* * Grace-period counter management. diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 419f3c38e1b6..142cdd4a50c9 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -818,6 +818,7 @@ static void rcu_eqs_enter(bool user) struct rcu_dynticks *rdtp; rdtp = this_cpu_ptr(&rcu_dynticks); + WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0); if ((rdtp->dynticks_nesting & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) @@ -1008,6 +1009,7 @@ static void rcu_eqs_exit(bool user) rcu_eqs_exit_common(DYNTICK_TASK_EXIT_IDLE, user); rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; __this_cpu_dec(disable_rcu_irq_enter); + WRITE_ONCE(rdtp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE); } } -- cgit v1.2.3