linux-imx

// SPDX-License-Identifier: GPL-2.0+

/*

 * Read-Copy Update mechanism for mutual exclusion

 *

 * Copyright IBM Corporation, 2001

 *

 * Authors: Dipankar Sarma <dipankar@in.ibm.com>

 *      Manfred Spraul <manfred@colorfullife.com>

 *

 * Based on the original work by Paul McKenney <paulmck@linux.ibm.com>

 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.

 * Papers:

 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf

 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)

 *

 * For detailed explanation of Read-Copy Update mechanism see -

 *      http://lse.sourceforge.net/locking/rcupdate.html

 *

 */

#include <linux/types.h>

#include <linux/kernel.h>

#include <linux/init.h>

#include <linux/spinlock.h>

#include <linux/smp.h>

#include <linux/interrupt.h>

#include <linux/sched/signal.h>

#include <linux/sched/debug.h>

#include <linux/atomic.h>

#include <linux/bitops.h>

#include <linux/percpu.h>

#include <linux/notifier.h>

#include <linux/cpu.h>

#include <linux/mutex.h>

#include <linux/export.h>

#include <linux/hardirq.h>

#include <linux/delay.h>

#include <linux/moduleparam.h>

#include <linux/kthread.h>

#include <linux/tick.h>

#include <linux/rcupdate_wait.h>

#include <linux/sched/isolation.h>

#include <linux/kprobes.h>

​

#define CREATE_TRACE_POINTS

​

#include "rcu.h"

​

#ifdef MODULE_PARAM_PREFIX

#undef MODULE_PARAM_PREFIX

#endif

#define MODULE_PARAM_PREFIX "rcupdate."

​

#ifndef CONFIG_TINY_RCU

extern int rcu_expedited; /* from sysctl */

module_param(rcu_expedited, int, 0);

extern int rcu_normal; /* from sysctl */

module_param(rcu_normal, int, 0);

static int rcu_normal_after_boot;

module_param(rcu_normal_after_boot, int, 0);

#endif /* #ifndef CONFIG_TINY_RCU */

​

#ifdef CONFIG_DEBUG_LOCK_ALLOC

/**

 * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?

 *

 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an

 * RCU-sched read-side critical section.  In absence of

 * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side

 * critical section unless it can prove otherwise.  Note that disabling

 * of preemption (including disabling irqs) counts as an RCU-sched

 * read-side critical section.  This is useful for debug checks in functions

 * that required that they be called within an RCU-sched read-side

 * critical section.

 *

 * Check debug_lockdep_rcu_enabled() to prevent false positives during boot

 * and while lockdep is disabled.

 *

 * Note that if the CPU is in the idle loop from an RCU point of

 * view (ie: that we are in the section between rcu_idle_enter() and

 * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU

 * did an rcu_read_lock().  The reason for this is that RCU ignores CPUs

 * that are in such a section, considering these as in extended quiescent

 * state, so such a CPU is effectively never in an RCU read-side critical

 * section regardless of what RCU primitives it invokes.  This state of

 * affairs is required --- we need to keep an RCU-free window in idle

 * where the CPU may possibly enter into low power mode. This way we can

 * notice an extended quiescent state to other CPUs that started a grace

 * period. Otherwise we would delay any grace period as long as we run in

 * the idle task.

 *

 * Similarly, we avoid claiming an SRCU read lock held if the current

 * CPU is offline.