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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-05-22 22:10:24 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-07-02 12:34:24 -0700
commit62fde6edf12b60fddb13a3f0a779c8be0bb7447e (patch)
tree2fa26e28ce311acb29c60f1595235240be6e7d97 /kernel
parent28f5c693d03530eb15c5354f758b789189b98c37 (diff)
downloadop-kernel-dev-62fde6edf12b60fddb13a3f0a779c8be0bb7447e.zip
op-kernel-dev-62fde6edf12b60fddb13a3f0a779c8be0bb7447e.tar.gz
rcu: Make __call_rcu() handle invocation from idle
Although __call_rcu() is handled correctly when called from a momentary non-idle period, if it is called on a CPU that RCU believes to be idle on RCU_FAST_NO_HZ kernels, the callback might be indefinitely postponed. This commit therefore ensures that RCU is aware of the new callback and has a chance to force the CPU out of dyntick-idle mode when a new callback is posted. Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcutree.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 89addad..a4a9c91 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -585,8 +585,6 @@ void rcu_nmi_exit(void)
WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
}
-#ifdef CONFIG_PROVE_RCU
-
/**
* rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
*
@@ -604,7 +602,7 @@ int rcu_is_cpu_idle(void)
}
EXPORT_SYMBOL(rcu_is_cpu_idle);
-#ifdef CONFIG_HOTPLUG_CPU
+#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
/*
* Is the current CPU online? Disable preemption to avoid false positives
@@ -645,9 +643,7 @@ bool rcu_lockdep_current_cpu_online(void)
}
EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
-#endif /* #ifdef CONFIG_PROVE_RCU */
+#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
/**
* rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
@@ -1904,6 +1900,13 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
else
trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
+ /*
+ * If called from an extended quiescent state, invoke the RCU
+ * core in order to force a re-evaluation of RCU's idleness.
+ */
+ if (rcu_is_cpu_idle())
+ invoke_rcu_core();
+
/* If interrupts were disabled, don't dive into RCU core. */
if (irqs_disabled_flags(flags)) {
local_irq_restore(flags);
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