/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Read-Copy Update mechanism for mutual exclusion (tree-based version)
* Internal non-public definitions that provide either classic
* or preemptible semantics.
*
* Copyright Red Hat, 2009
* Copyright IBM Corporation, 2009
*
* Author: Ingo Molnar <mingo@elte.hu>
* Paul E. McKenney <paulmck@linux.ibm.com>
*/
#include "../locking/rtmutex_common.h"
static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
{
/*
* In order to read the offloaded state of an rdp in a safe
* and stable way and prevent from its value to be changed
* under us, we must either hold the barrier mutex, the cpu
* hotplug lock (read or write) or the nocb lock. Local
* non-preemptible reads are also safe. NOCB kthreads and
* timers have their own means of synchronization against the
* offloaded state updaters.
*/
RCU_NOCB_LOCKDEP_WARN(
!(lockdep_is_held(&rcu_state.barrier_mutex) ||
(IS_ENABLED(CONFIG_HOTPLUG_CPU) && lockdep_is_cpus_held()) ||
lockdep_is_held(&rdp->nocb_lock) ||
lockdep_is_held(&rcu_state.nocb_mutex) ||
((!(IS_ENABLED(CONFIG_PREEMPT_COUNT) && preemptible()) || softirq_count()) &&
rdp == this_cpu_ptr(&rcu_data)) ||
rcu_current_is_nocb_kthread(rdp)),
"Unsafe read of RCU_NOCB offloaded state"
);
return rcu_segcblist_is_offloaded(&rdp->cblist);
}
/*
* Check the RCU kernel configuration parameters and print informative
* messages about anything out of the ordinary.
*/
static void __init rcu_bootup_announce_oddness(void)
{
if (IS_ENABLED(CONFIG_RCU_TRACE))
pr_info("\tRCU event tracing is enabled.\n");
if ((IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 64) ||
(!IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 32))
pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d.\n",
RCU_FANOUT);
if (rcu_fanout_exact)
pr_info("\tHierarchical RCU autobalancing is disabled.\n");
if (IS_ENABLED(CONFIG_PROVE_RCU))
pr_info("\tRCU lockdep checking is enabled.\n");
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
pr_info("\tRCU strict (and thus non-scalable) grace periods are enabled.\n");
if (RCU_NUM_LVLS >= 4)
pr_info("\tFour(or more)-level hierarchy is enabled.