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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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>
 #include <linux/slab.h>
 #include <linux/irq_work.h>
 #include <linux/rcupdate_trace.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
 module_param(rcu_expedited, int, 0444);
 module_param(rcu_normal, int, 0444);
 static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT);
 #if !defined(CONFIG_PREEMPT_RT) || defined(CONFIG_NO_HZ_FULL)
 module_param(rcu_normal_after_boot, int, 0444);
 #endif
 #endif /* #ifndef CONFIG_TINY_RCU */
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 /**
  * rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section?
  * @ret:    Best guess answer if lockdep cannot be relied on
  *
  * Returns true if lockdep must be ignored, in which case ``*ret`` contains
  * the best guess described below.  Otherwise returns false, in which
  * case ``*ret`` tells the caller nothing and the caller should instead
  * consult lockdep.
  *
  * If CONFIG_DEBUG_LOCK_ALLOC is selected, set ``*ret`` to 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 ct_idle_enter() and ct_idle_exit())
  * then rcu_read_lock_held() sets ``*ret`` to 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 RCU read lock held if the current
  * CPU is offline.
  */
 static bool rcu_read_lock_held_common(bool *ret)
 {
     if (!debug_lockdep_rcu_enabled()) {
         *ret = true;
         return true;
     }
     if (!rcu_is_watching()) {
         *ret = false;
         return true;
     }
     if (!rcu_lockdep_current_cpu_online()) {
         *ret = false;
         return true;
     }
     return false;
 }
 
 int rcu_read_lock_sched_held(void)
 {
     bool ret;
 
     if (rcu_read_lock_held_common(&ret))
         return ret;
     return lock_is_held(&rcu_sched_lock_map) || !preemptible();
 }
 EXPORT_SYMBOL(rcu_read_lock_sched_held);
 #endif
 
 #ifndef CONFIG_TINY_RCU
 
 /*
  * Should expedited grace-period primitives always fall back to their
  * non-expedited counterparts?  Intended for use within RCU.  Note
  * that if the user specifies both rcu_expedited and rcu_normal, then
  * rcu_normal wins.  (Except during the time period during boot from
  * when the first task is spawned until the rcu_set_runtime_mode()
  * core_initcall() is invoked, at which point everything is expedited.)
  */
 bool rcu_gp_is_normal(void)
 {
     return READ_ONCE(rcu_normal) &&
            rcu_scheduler_active != RCU_SCHEDULER_INIT;
 }
 EXPORT_SYMBOL_GPL(rcu_gp_is_normal);
 
 static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1);
 
 /*
  * Should normal grace-period primitives be expedited?  Intended for
  * use within RCU.  Note that this function takes the rcu_expedited
  * sysfs/boot variable and rcu_scheduler_active into account as well
  * as the rcu_expedite_gp() nesting.  So looping on rcu_unexpedite_gp()
  * until rcu_gp_is_expedited() returns false is a -really- bad idea.
  */
 bool rcu_gp_is_expedited(void)
 {
     return rcu_expedited || atomic_read(&rcu_expedited_nesting);
 }
 EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
 
 /**
  * rcu_expedite_gp - Expedite future RCU grace periods
  *
  * After a call to this function, future calls to synchronize_rcu() and
  * friends act as the corresponding synchronize_rcu_expedited() function
  * had instead been called.
  */
 void rcu_expedite_gp(void)
 {
     atomic_inc(&rcu_expedited_nesting);
 }
 EXPORT_SYMBOL_GPL(rcu_expedite_gp);
 
 /**
  * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
  *
  * Undo a prior call to rcu_expedite_gp().  If all prior calls to
  * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
  * and if the rcu_expedited sysfs/boot parameter is not set, then all
  * subsequent calls to synchronize_rcu() and friends will return to
  * their normal non-expedited behavior.
  */
 void rcu_unexpedite_gp(void)
 {
     atomic_dec(&rcu_expedited_nesting);
 }
 EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
 
 static bool rcu_boot_ended __read_mostly;
 
 /*
  * Inform RCU of the end of the in-kernel boot sequence.
  */
 void rcu_end_inkernel_boot(void)
 {
     rcu_unexpedite_gp();
     if (rcu_normal_after_boot)
         WRITE_ONCE(rcu_normal, 1);
     rcu_boot_ended = true;
 }
 
 /*
  * Let rcutorture know when it is OK to turn it up to eleven.
  */
 bool rcu_inkernel_boot_has_ended(void)
 {
     return rcu_boot_ended;
 }
 EXPORT_SYMBOL_GPL(rcu_inkernel_boot_has_ended);
 
 #endif /* #ifndef CONFIG_TINY_RCU */
 
 /*
  * Test each non-SRCU synchronous grace-period wait API.  This is
  * useful just after a change in mode for these primitives, and
  * during early boot.
  */
 void rcu_test_sync_prims(void)
 {
     if (!IS_ENABLED(CONFIG_PROVE_RCU))
         return;
     synchronize_rcu();
     synchronize_rcu_expedited();
 }
 
 #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU)
 
 /*
  * Switch to run-time mode once RCU has fully initialized.
  */
 static int __init rcu_set_runtime_mode(void)
 {
     rcu_test_sync_prims();
     rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
     kfree_rcu_scheduler_running();
     rcu_test_sync_prims();
     return 0;
 }
 core_initcall(rcu_set_runtime_mode);
 
 #endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 static struct lock_class_key rcu_lock_key;
 struct lockdep_map rcu_lock_map = {
     .name = "rcu_read_lock",
     .key = &rcu_lock_key,
     .wait_type_outer = LD_WAIT_FREE,
     .wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT implies PREEMPT_RCU */
 };
 EXPORT_SYMBOL_GPL(rcu_lock_map);
 
 static struct lock_class_key rcu_bh_lock_key;
 struct lockdep_map rcu_bh_lock_map = {
     .name = "rcu_read_lock_bh",
     .key = &rcu_bh_lock_key,
     .wait_type_outer = LD_WAIT_FREE,
     .wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */
 };
 EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
 
 static struct lock_class_key rcu_sched_lock_key;
 struct lockdep_map rcu_sched_lock_map = {
     .name = "rcu_read_lock_sched",
     .key = &rcu_sched_lock_key,
     .wait_type_outer = LD_WAIT_FREE,
     .wait_type_inner = LD_WAIT_SPIN,
 };
 EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
 
 // Tell lockdep when RCU callbacks are being invoked.
 static struct lock_class_key rcu_callback_key;
 struct lockdep_map rcu_callback_map =
     STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
 EXPORT_SYMBOL_GPL(rcu_callback_map);
 
 noinstr int notrace debug_lockdep_rcu_enabled(void)
 {
     return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && READ_ONCE(debug_locks) &&
            current->lockdep_recursion == 0;
 }
 EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
 
 /**
  * rcu_read_lock_held() - might we be in RCU read-side critical section?
  *
  * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
  * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
  * this assumes we are in an RCU read-side critical section unless it can
  * prove otherwise.  This is useful for debug checks in functions that
  * require that they be called within an RCU read-side critical section.
  *
  * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
  * and while lockdep is disabled.
  *
  * Note that rcu_read_lock() and the matching rcu_read_unlock() must
  * occur in the same context, for example, it is illegal to invoke
  * rcu_read_unlock() in process context if the matching rcu_read_lock()
  * was invoked from within an irq handler.
  *
  * Note that rcu_read_lock() is disallowed if the CPU is either idle or
  * offline from an RCU perspective, so check for those as well.
  */
 int rcu_read_lock_held(void)
 {
     bool ret;
 
     if (rcu_read_lock_held_common(&ret))
         return ret;
     return lock_is_held(&rcu_lock_map);
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_held);
 
 /**
  * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
  *
  * Check for bottom half being disabled, which covers both the
  * CONFIG_PROVE_RCU and not cases.  Note that if someone uses
  * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
  * will show the situation.  This is useful for debug checks in functions
  * that require that they be called within an RCU read-side critical
  * section.
  *
  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
  *
  * Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or
  * offline from an RCU perspective, so check for those as well.
  */
 int rcu_read_lock_bh_held(void)
 {
     bool ret;
 
     if (rcu_read_lock_held_common(&ret))
         return ret;
     return in_softirq() || irqs_disabled();
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
 
 int rcu_read_lock_any_held(void)
 {
     bool ret;
 
     if (rcu_read_lock_held_common(&ret))
         return ret;
     if (lock_is_held(&rcu_lock_map) ||
         lock_is_held(&rcu_bh_lock_map) ||
         lock_is_held(&rcu_sched_lock_map))
         return 1;
     return !preemptible();
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);
 
 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 /**
  * wakeme_after_rcu() - Callback function to awaken a task after grace period
  * @head: Pointer to rcu_head member within rcu_synchronize structure
  *
  * Awaken the corresponding task now that a grace period has elapsed.
  */
 void wakeme_after_rcu(struct rcu_head *head)
 {
     struct rcu_synchronize *rcu;
 
     rcu = container_of(head, struct rcu_synchronize, head);
     complete(&rcu->completion);
 }
 EXPORT_SYMBOL_GPL(wakeme_after_rcu);
 
 void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
            struct rcu_synchronize *rs_array)
 {
     int i;
     int j;
 
     /* Initialize and register callbacks for each crcu_array element. */
     for (i = 0; i < n; i++) {
         if (checktiny &&
             (crcu_array[i] == call_rcu)) {
             might_sleep();
             continue;
         }
         for (j = 0; j < i; j++)
             if (crcu_array[j] == crcu_array[i])
                 break;
         if (j == i) {
             init_rcu_head_on_stack(&rs_array[i].head);
             init_completion(&rs_array[i].completion);
             (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
         }
     }
 
     /* Wait for all callbacks to be invoked. */
     for (i = 0; i < n; i++) {
         if (checktiny &&
             (crcu_array[i] == call_rcu))
             continue;
         for (j = 0; j < i; j++)
             if (crcu_array[j] == crcu_array[i])
                 break;
         if (j == i) {
             wait_for_completion(&rs_array[i].completion);
             destroy_rcu_head_on_stack(&rs_array[i].head);
         }
     }
 }
 EXPORT_SYMBOL_GPL(__wait_rcu_gp);
 
 void finish_rcuwait(struct rcuwait *w)
 {
     rcu_assign_pointer(w->task, NULL);
     __set_current_state(TASK_RUNNING);
 }
 EXPORT_SYMBOL_GPL(finish_rcuwait);
 
 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
 void init_rcu_head(struct rcu_head *head)
 {
     debug_object_init(head, &rcuhead_debug_descr);
 }
 EXPORT_SYMBOL_GPL(init_rcu_head);
 
 void destroy_rcu_head(struct rcu_head *head)
 {
     debug_object_free(head, &rcuhead_debug_descr);
 }
 EXPORT_SYMBOL_GPL(destroy_rcu_head);
 
 static bool rcuhead_is_static_object(void *addr)
 {
     return true;
 }
 
 /**
  * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
  * @head: pointer to rcu_head structure to be initialized
  *
  * This function informs debugobjects of a new rcu_head structure that
  * has been allocated as an auto variable on the stack.  This function
  * is not required for rcu_head structures that are statically defined or
  * that are dynamically allocated on the heap.  This function has no
  * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
  */
 void init_rcu_head_on_stack(struct rcu_head *head)
 {
     debug_object_init_on_stack(head, &rcuhead_debug_descr);
 }
 EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
 
 /**
  * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
  * @head: pointer to rcu_head structure to be initialized
  *
  * This function informs debugobjects that an on-stack rcu_head structure
  * is about to go out of scope.  As with init_rcu_head_on_stack(), this
  * function is not required for rcu_head structures that are statically
  * defined or that are dynamically allocated on the heap.  Also as with
  * init_rcu_head_on_stack(), this function has no effect for
  * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
  */
 void destroy_rcu_head_on_stack(struct rcu_head *head)
 {
     debug_object_free(head, &rcuhead_debug_descr);
 }
 EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
 
 const struct debug_obj_descr rcuhead_debug_descr = {
     .name = "rcu_head",
     .is_static_object = rcuhead_is_static_object,
 };
 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE)
 void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
                    unsigned long secs,
                    unsigned long c_old, unsigned long c)
 {
     trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
 }
 EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
 #else
 #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
     do { } while (0)
 #endif
 
 #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
 /* Get rcutorture access to sched_setaffinity(). */
 long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
 {
     int ret;
 
     ret = sched_setaffinity(pid, in_mask);
     WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n", __func__, ret);
     return ret;
 }
 EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity);
 #endif
 
 #ifdef CONFIG_RCU_STALL_COMMON
 int rcu_cpu_stall_ftrace_dump __read_mostly;
 module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
 int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings.
 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
 module_param(rcu_cpu_stall_suppress, int, 0644);
 int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
 module_param(rcu_cpu_stall_timeout, int, 0644);
 int rcu_exp_cpu_stall_timeout __read_mostly = CONFIG_RCU_EXP_CPU_STALL_TIMEOUT;
 module_param(rcu_exp_cpu_stall_timeout, int, 0644);
 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
 
 // Suppress boot-time RCU CPU stall warnings and rcutorture writer stall
 // warnings.  Also used by rcutorture even if stall warnings are excluded.
 int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls.
 EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot);
 module_param(rcu_cpu_stall_suppress_at_boot, int, 0444);
 
 /**
  * get_completed_synchronize_rcu - Return a pre-completed polled state cookie
  *
  * Returns a value that will always be treated by functions like
  * poll_state_synchronize_rcu() as a cookie whose grace period has already
  * completed.
  */
 unsigned long get_completed_synchronize_rcu(void)
 {
     return RCU_GET_STATE_COMPLETED;
 }
 EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu);
 
 #ifdef CONFIG_PROVE_RCU
 
 /*
  * Early boot self test parameters.
  */
 static bool rcu_self_test;
 module_param(rcu_self_test, bool, 0444);
 
 static int rcu_self_test_counter;
 
 static void test_callback(struct rcu_head *r)
 {
     rcu_self_test_counter++;
     pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
 }
 
 DEFINE_STATIC_SRCU(early_srcu);
 static unsigned long early_srcu_cookie;
 
 struct early_boot_kfree_rcu {
     struct rcu_head rh;
 };
 
 static void early_boot_test_call_rcu(void)
 {
     static struct rcu_head head;
     static struct rcu_head shead;
     struct early_boot_kfree_rcu *rhp;
 
     call_rcu(&head, test_callback);
     if (IS_ENABLED(CONFIG_SRCU)) {
         early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
         call_srcu(&early_srcu, &shead, test_callback);
     }
     rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
     if (!WARN_ON_ONCE(!rhp))
         kfree_rcu(rhp, rh);
 }
 
 void rcu_early_boot_tests(void)
 {
     pr_info("Running RCU self tests\n");
 
     if (rcu_self_test)
         early_boot_test_call_rcu();
     rcu_test_sync_prims();
 }
 
 static int rcu_verify_early_boot_tests(void)
 {
     int ret = 0;
     int early_boot_test_counter = 0;
 
     if (rcu_self_test) {
         early_boot_test_counter++;
         rcu_barrier();
         if (IS_ENABLED(CONFIG_SRCU)) {
             early_boot_test_counter++;
             srcu_barrier(&early_srcu);
             WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
         }
     }
     if (rcu_self_test_counter != early_boot_test_counter) {
         WARN_ON(1);
         ret = -1;
     }
 
     return ret;
 }
 late_initcall(rcu_verify_early_boot_tests);
 #else
 void rcu_early_boot_tests(void) {}
 #endif /* CONFIG_PROVE_RCU */
 
 #include "tasks.h"
 
 #ifndef CONFIG_TINY_RCU
 
 /*
  * Print any significant non-default boot-time settings.
  */
 void __init rcupdate_announce_bootup_oddness(void)
 {
     if (rcu_normal)
         pr_info("\tNo expedited grace period (rcu_normal).\n");
     else if (rcu_normal_after_boot)
         pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n");
     else if (rcu_expedited)
         pr_info("\tAll grace periods are expedited (rcu_expedited).\n");
     if (rcu_cpu_stall_suppress)
         pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n");
     if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT)
         pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout);
     rcu_tasks_bootup_oddness();
 }
 
 #endif /* #ifndef CONFIG_TINY_RCU */

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