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

  /*
   * Read-Copy Update mechanism for mutual exclusion (tree-based version)
   * Internal non-public definitions.
   *

   * Copyright IBM Corporation, 2008
   *
   * Author: Ingo Molnar <mingo@elte.hu>

   *	   Paul E. McKenney <paulmck@linux.ibm.com>

   */
  
  #include <linux/cache.h>
  #include <linux/spinlock.h>

  #include <linux/rtmutex.h>

  #include <linux/threads.h>
  #include <linux/cpumask.h>
  #include <linux/seqlock.h>

  #include <linux/swait.h>

  #include <linux/rcu_node_tree.h>

  #include "rcu_segcblist.h"

  /* Communicate arguments to a workqueue handler. */
  struct rcu_exp_work {

  	unsigned long rew_s;
  	struct work_struct rew_work;
  };

  /* RCU's kthread states for tracing. */
  #define RCU_KTHREAD_STOPPED  0
  #define RCU_KTHREAD_RUNNING  1
  #define RCU_KTHREAD_WAITING  2

  #define RCU_KTHREAD_OFFCPU   3
  #define RCU_KTHREAD_YIELDING 4
  #define RCU_KTHREAD_MAX      4

  /*
   * Definition for node within the RCU grace-period-detection hierarchy.
   */
  struct rcu_node {

  	raw_spinlock_t __private lock;	/* Root rcu_node's lock protects */
  					/*  some rcu_state fields as well as */
  					/*  following. */

  	unsigned long gp_seq;	/* Track rsp->gp_seq. */

  	unsigned long gp_seq_needed; /* Track furthest future GP request. */

  	unsigned long completedqs; /* All QSes done for this node. */

  	unsigned long qsmask;	/* CPUs or groups that need to switch in */
  				/*  order for current grace period to proceed.*/

  				/*  In leaf rcu_node, each bit corresponds to */
  				/*  an rcu_data structure, otherwise, each */
  				/*  bit corresponds to a child rcu_node */
  				/*  structure. */

  	unsigned long rcu_gp_init_mask;	/* Mask of offline CPUs at GP init. */

  	unsigned long qsmaskinit;

  				/* Per-GP initial value for qsmask. */

  				/*  Initialized from ->qsmaskinitnext at the */
  				/*  beginning of each grace period. */
  	unsigned long qsmaskinitnext;
  				/* Online CPUs for next grace period. */

  	unsigned long expmask;	/* CPUs or groups that need to check in */
  				/*  to allow the current expedited GP */
  				/*  to complete. */
  	unsigned long expmaskinit;
  				/* Per-GP initial values for expmask. */
  				/*  Initialized from ->expmaskinitnext at the */
  				/*  beginning of each expedited GP. */
  	unsigned long expmaskinitnext;
  				/* Online CPUs for next expedited GP. */

  				/*  Any CPU that has ever been online will */
  				/*  have its bit set. */

  	unsigned long cbovldmask;
  				/* CPUs experiencing callback overload. */

  	unsigned long ffmask;	/* Fully functional CPUs. */

  	unsigned long grpmask;	/* Mask to apply to parent qsmask. */

  				/*  Only one bit will be set in this mask. */

  	int	grplo;		/* lowest-numbered CPU here. */
  	int	grphi;		/* highest-numbered CPU here. */

  	u8	grpnum;		/* group number for next level up. */

  	u8	level;		/* root is at level 0. */

  	bool	wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
  				/*  exit RCU read-side critical sections */
  				/*  before propagating offline up the */
  				/*  rcu_node tree? */

  	struct rcu_node *parent;

  	struct list_head blkd_tasks;
  				/* Tasks blocked in RCU read-side critical */
  				/*  section.  Tasks are placed at the head */
  				/*  of this list and age towards the tail. */
  	struct list_head *gp_tasks;
  				/* Pointer to the first task blocking the */
  				/*  current grace period, or NULL if there */
  				/*  is no such task. */
  	struct list_head *exp_tasks;
  				/* Pointer to the first task blocking the */
  				/*  current expedited grace period, or NULL */
  				/*  if there is no such task.  If there */
  				/*  is no current expedited grace period, */
  				/*  then there can cannot be any such task. */

  	struct list_head *boost_tasks;
  				/* Pointer to first task that needs to be */
  				/*  priority boosted, or NULL if no priority */
  				/*  boosting is needed for this rcu_node */
  				/*  structure.  If there are no tasks */
  				/*  queued on this rcu_node structure that */
  				/*  are blocking the current grace period, */
  				/*  there can be no such task. */

  	struct rt_mutex boost_mtx;
  				/* Used only for the priority-boosting */
  				/*  side effect, not as a lock. */

  	unsigned long boost_time;
  				/* When to start boosting (jiffies). */
  	struct task_struct *boost_kthread_task;
  				/* kthread that takes care of priority */
  				/*  boosting for this rcu_node structure. */

  	unsigned int boost_kthread_status;
  				/* State of boost_kthread_task for tracing. */

  #ifdef CONFIG_RCU_NOCB_CPU

  	struct swait_queue_head nocb_gp_wq[2];

  				/* Place for rcu_nocb_kthread() to wait GP. */

  #endif /* #ifdef CONFIG_RCU_NOCB_CPU */

  	raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;

  	spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
  	unsigned long exp_seq_rq;

  	wait_queue_head_t exp_wq[4];

  	struct rcu_exp_work rew;
  	bool exp_need_flush;	/* Need to flush workitem? */

  } ____cacheline_internodealigned_in_smp;

  /*

   * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
   * are indexed relative to this interval rather than the global CPU ID space.
   * This generates the bit for a CPU in node-local masks.
   */

  #define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))

  
  /*

   * Union to allow "aggregate OR" operation on the need for a quiescent
   * state by the normal and expedited grace periods.
   */
  union rcu_noqs {
  	struct {
  		u8 norm;
  		u8 exp;
  	} b; /* Bits. */
  	u16 s; /* Set of bits, aggregate OR here. */
  };

  /* Per-CPU data for read-copy update. */
  struct rcu_data {
  	/* 1) quiescent-state and grace-period handling : */

  	unsigned long	gp_seq;		/* Track rsp->gp_seq counter. */

  	unsigned long	gp_seq_needed;	/* Track furthest future GP request. */

  	union rcu_noqs	cpu_no_qs;	/* No QSes yet for this CPU. */

  	bool		core_needs_qs;	/* Core waits for quiesc state. */

  	bool		beenonline;	/* CPU online at least once. */

  	bool		gpwrap;		/* Possible ->gp_seq wrap. */

  	bool		exp_deferred_qs; /* This CPU awaiting a deferred QS? */

  	bool		cpu_started;	/* RCU watching this onlining CPU. */

  	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
  	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */

  	unsigned long	ticks_this_gp;	/* The number of scheduling-clock */
  					/*  ticks this CPU has handled */
  					/*  during and after the last grace */
  					/* period it is aware of. */

  	struct irq_work defer_qs_iw;	/* Obtain later scheduler attention. */
  	bool defer_qs_iw_pending;	/* Scheduler attention pending? */

  	struct work_struct strict_work;	/* Schedule readers for strict GPs. */

  
  	/* 2) batch handling */

  	struct rcu_segcblist cblist;	/* Segmented callback list, with */
  					/* different callbacks waiting for */
  					/* different grace periods. */

  	long		qlen_last_fqs_check;
  					/* qlen at last check for QS forcing */

  	unsigned long	n_cbs_invoked;	/* # callbacks invoked since boot. */

  	unsigned long	n_force_qs_snap;
  					/* did other CPU force QS recently? */

  	long		blimit;		/* Upper limit on a processed batch */

  	/* 3) dynticks interface. */

  	int dynticks_snap;		/* Per-GP tracking for dynticks. */

  	long dynticks_nesting;		/* Track process nesting level. */
  	long dynticks_nmi_nesting;	/* Track irq/NMI nesting level. */
  	atomic_t dynticks;		/* Even value for idle, else odd. */
  	bool rcu_need_heavy_qs;		/* GP old, so heavy quiescent state! */
  	bool rcu_urgent_qs;		/* GP old need light quiescent state. */

  	bool rcu_forced_tick;		/* Forced tick to provide QS. */

  	bool rcu_forced_tick_exp;	/*   ... provide QS to expedited GP. */

  #ifdef CONFIG_RCU_FAST_NO_HZ

  	unsigned long last_accelerate;	/* Last jiffy CBs were accelerated. */
  	unsigned long last_advance_all;	/* Last jiffy CBs were all advanced. */
  	int tick_nohz_enabled_snap;	/* Previously seen value from sysfs. */

  #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */

  	/* 4) rcu_barrier(), OOM callbacks, and expediting. */

  	struct rcu_head barrier_head;

  	int exp_dynticks_snap;		/* Double-check need for IPI. */

  	/* 5) Callback offloading. */

  #ifdef CONFIG_RCU_NOCB_CPU

  	struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
  	struct task_struct *nocb_gp_kthread;

  	raw_spinlock_t nocb_lock;	/* Guard following pair of fields. */

  	atomic_t nocb_lock_contended;	/* Contention experienced. */

  	int nocb_defer_wakeup;		/* Defer wakeup of nocb_kthread. */

  	struct timer_list nocb_timer;	/* Enforce finite deferral. */

  	unsigned long nocb_gp_adv_time;	/* Last call_rcu() CB adv (jiffies). */
  
  	/* The following fields are used by call_rcu, hence own cacheline. */
  	raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
  	struct rcu_cblist nocb_bypass;	/* Lock-contention-bypass CB list. */
  	unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
  	unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
  	int nocb_nobypass_count;	/* # ->cblist enqueues at ^^^ time. */

  	/* The following fields are used by GP kthread, hence own cacheline. */

  	raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;

  	struct timer_list nocb_bypass_timer; /* Force nocb_bypass flush. */

  	u8 nocb_gp_sleep;		/* Is the nocb GP thread asleep? */
  	u8 nocb_gp_bypass;		/* Found a bypass on last scan? */
  	u8 nocb_gp_gp;			/* GP to wait for on last scan? */
  	unsigned long nocb_gp_seq;	/*  If so, ->gp_seq to wait for. */
  	unsigned long nocb_gp_loops;	/* # passes through wait code. */

  	struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */

  	bool nocb_cb_sleep;		/* Is the nocb CB thread asleep? */

  	struct task_struct *nocb_cb_kthread;

  	struct rcu_data *nocb_next_cb_rdp;
  					/* Next rcu_data in wakeup chain. */

  	/* The following fields are used by CB kthread, hence new cacheline. */

  	struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;

  					/* GP rdp takes GP-end wakeups. */

  #endif /* #ifdef CONFIG_RCU_NOCB_CPU */

  	/* 6) RCU priority boosting. */
  	struct task_struct *rcu_cpu_kthread_task;
  					/* rcuc per-CPU kthread or NULL. */

  	unsigned int rcu_cpu_kthread_status;

  	char rcu_cpu_has_work;

  
  	/* 7) Diagnostic data, including RCU CPU stall warnings. */

  	unsigned int softirq_snap;	/* Snapshot of softirq activity. */

  	/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
  	struct irq_work rcu_iw;		/* Check for non-irq activity. */
  	bool rcu_iw_pending;		/* Is ->rcu_iw pending? */

  	unsigned long rcu_iw_gp_seq;	/* ->gp_seq associated with ->rcu_iw. */

  	unsigned long rcu_ofl_gp_seq;	/* ->gp_seq at last offline. */
  	short rcu_ofl_gp_flags;		/* ->gp_flags at last offline. */
  	unsigned long rcu_onl_gp_seq;	/* ->gp_seq at last online. */
  	short rcu_onl_gp_flags;		/* ->gp_flags at last online. */

  	unsigned long last_fqs_resched;	/* Time of last rcu_resched(). */

  	int cpu;
  };

  /* Values for nocb_defer_wakeup field in struct rcu_data. */

  #define RCU_NOCB_WAKE_NOT	0
  #define RCU_NOCB_WAKE		1
  #define RCU_NOCB_WAKE_FORCE	2

  #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
  					/* For jiffies_till_first_fqs and */
  					/*  and jiffies_till_next_fqs. */

  #define RCU_JIFFIES_FQS_DIV	256	/* Very large systems need more */
  					/*  delay between bouts of */
  					/*  quiescent-state forcing. */
  
  #define RCU_STALL_RAT_DELAY	2	/* Allow other CPUs time to take */
  					/*  at least one scheduling clock */
  					/*  irq before ratting on them. */

  #define rcu_wait(cond)							\
  do {									\
  	for (;;) {							\
  		set_current_state(TASK_INTERRUPTIBLE);			\
  		if (cond)						\
  			break;						\
  		schedule();						\
  	}								\
  	__set_current_state(TASK_RUNNING);				\
  } while (0)

  
  /*
   * RCU global state, including node hierarchy.  This hierarchy is
   * represented in "heap" form in a dense array.  The root (first level)
   * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
   * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
   * and the third level in ->node[m+1] and following (->node[m+1] referenced
   * by ->level[2]).  The number of levels is determined by the number of
   * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
   * consisting of a single rcu_node.
   */
  struct rcu_state {
  	struct rcu_node node[NUM_RCU_NODES];	/* Hierarchy. */

  	struct rcu_node *level[RCU_NUM_LVLS + 1];
  						/* Hierarchy levels (+1 to */
  						/*  shut bogus gcc warning) */

  	int ncpus;				/* # CPUs seen so far. */

  
  	/* The following fields are guarded by the root rcu_node's lock. */

  	u8	boost ____cacheline_internodealigned_in_smp;
  						/* Subject to priority boost. */

  	unsigned long gp_seq;			/* Grace-period sequence #. */

  	unsigned long gp_max;			/* Maximum GP duration in */
  						/*  jiffies. */

  	struct task_struct *gp_kthread;		/* Task for grace periods. */

  	struct swait_queue_head gp_wq;		/* Where GP task waits. */

  	short gp_flags;				/* Commands for GP task. */
  	short gp_state;				/* GP kthread sleep state. */

  	unsigned long gp_wake_time;		/* Last GP kthread wake. */
  	unsigned long gp_wake_seq;		/* ->gp_seq at ^^^. */

  	/* End of fields guarded by root rcu_node's lock. */

  	struct mutex barrier_mutex;		/* Guards barrier fields. */

  	atomic_t barrier_cpu_count;		/* # CPUs waiting on. */

  	struct completion barrier_completion;	/* Wake at barrier end. */

  	unsigned long barrier_sequence;		/* ++ at start and end of */

  						/*  rcu_barrier(). */

  	/* End of fields guarded by barrier_mutex. */

  	struct mutex exp_mutex;			/* Serialize expedited GP. */

  	struct mutex exp_wake_mutex;		/* Serialize wakeup. */

  	unsigned long expedited_sequence;	/* Take a ticket. */

  	atomic_t expedited_need_qs;		/* # CPUs left to check in. */

  	struct swait_queue_head expedited_wq;	/* Wait for check-ins. */

  	int ncpus_snap;				/* # CPUs seen last time. */

  	u8 cbovld;				/* Callback overload now? */
  	u8 cbovldnext;				/* ^        ^  next time? */

  	unsigned long jiffies_force_qs;		/* Time at which to invoke */
  						/*  force_quiescent_state(). */

  	unsigned long jiffies_kick_kthreads;	/* Time at which to kick */
  						/*  kthreads, if configured. */

  	unsigned long n_force_qs;		/* Number of calls to */
  						/*  force_quiescent_state(). */

  	unsigned long gp_start;			/* Time at which GP started, */
  						/*  but in jiffies. */

  	unsigned long gp_end;			/* Time last GP ended, again */
  						/*  in jiffies. */

  	unsigned long gp_activity;		/* Time of last GP kthread */
  						/*  activity in jiffies. */

  	unsigned long gp_req_activity;		/* Time of last GP request */
  						/*  in jiffies. */

  	unsigned long jiffies_stall;		/* Time at which to check */
  						/*  for CPU stalls. */

  	unsigned long jiffies_resched;		/* Time at which to resched */
  						/*  a reluctant CPU. */

  	unsigned long n_force_qs_gpstart;	/* Snapshot of n_force_qs at */
  						/*  GP start. */

  	const char *name;			/* Name of structure. */

  	char abbr;				/* Abbreviated name. */

  	raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;

  						/* Synchronize offline with */
  						/*  GP pre-initialization. */

  };

  /* Values for rcu_state structure's gp_flags field. */
  #define RCU_GP_FLAG_INIT 0x1	/* Need grace-period initialization. */
  #define RCU_GP_FLAG_FQS  0x2	/* Need grace-period quiescent-state forcing. */

  #define RCU_GP_FLAG_OVLD 0x4	/* Experiencing callback overload. */

  /* Values for rcu_state structure's gp_state field. */

  #define RCU_GP_IDLE	 0	/* Initial state and no GP in progress. */

  #define RCU_GP_WAIT_GPS  1	/* Wait for grace-period start. */

  #define RCU_GP_DONE_GPS  2	/* Wait done for grace-period start. */

  #define RCU_GP_ONOFF     3	/* Grace-period initialization hotplug. */
  #define RCU_GP_INIT      4	/* Grace-period initialization. */
  #define RCU_GP_WAIT_FQS  5	/* Wait for force-quiescent-state time. */
  #define RCU_GP_DOING_FQS 6	/* Wait done for force-quiescent-state time. */
  #define RCU_GP_CLEANUP   7	/* Grace-period cleanup started. */
  #define RCU_GP_CLEANED   8	/* Grace-period cleanup complete. */

  /*
   * In order to export the rcu_state name to the tracing tools, it
   * needs to be added in the __tracepoint_string section.
   * This requires defining a separate variable tp_<sname>_varname
   * that points to the string being used, and this will allow
   * the tracing userspace tools to be able to decipher the string
   * address to the matching string.
   */
  #ifdef CONFIG_PREEMPT_RCU
  #define RCU_ABBR 'p'
  #define RCU_NAME_RAW "rcu_preempt"
  #else /* #ifdef CONFIG_PREEMPT_RCU */
  #define RCU_ABBR 's'
  #define RCU_NAME_RAW "rcu_sched"
  #endif /* #else #ifdef CONFIG_PREEMPT_RCU */
  #ifndef CONFIG_TRACING
  #define RCU_NAME RCU_NAME_RAW
  #else /* #ifdef CONFIG_TRACING */
  static char rcu_name[] = RCU_NAME_RAW;
  static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
  #define RCU_NAME rcu_name
  #endif /* #else #ifdef CONFIG_TRACING */

  /* Forward declarations for tree_plugin.h */

  static void rcu_bootup_announce(void);

  static void rcu_qs(void);

  static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);

  #ifdef CONFIG_HOTPLUG_CPU

  static bool rcu_preempt_has_tasks(struct rcu_node *rnp);

  #endif /* #ifdef CONFIG_HOTPLUG_CPU */

  static int rcu_print_task_exp_stall(struct rcu_node *rnp);

  static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);

  static void rcu_flavor_sched_clock_irq(int user);

  static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);

  static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);

  static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);

  static bool rcu_is_callbacks_kthread(void);

  static void rcu_cpu_kthread_setup(unsigned int cpu);

  static void __init rcu_spawn_boost_kthreads(void);

  static void rcu_prepare_kthreads(int cpu);

  static void rcu_cleanup_after_idle(void);

  static void rcu_prepare_for_idle(void);

  static bool rcu_preempt_has_tasks(struct rcu_node *rnp);

  static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
  static void rcu_preempt_deferred_qs(struct task_struct *t);

  static void zero_cpu_stall_ticks(struct rcu_data *rdp);

  static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
  static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);

  static void rcu_init_one_nocb(struct rcu_node *rnp);

  static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
  				  unsigned long j);
  static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
  				bool *was_alldone, unsigned long flags);

  static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
  				 unsigned long flags);

  static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);

  static void do_nocb_deferred_wakeup(struct rcu_data *rdp);

  static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);

  static void rcu_spawn_cpu_nocb_kthread(int cpu);

  static void __init rcu_spawn_nocb_kthreads(void);

  static void show_rcu_nocb_state(struct rcu_data *rdp);

  static void rcu_nocb_lock(struct rcu_data *rdp);
  static void rcu_nocb_unlock(struct rcu_data *rdp);
  static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
  				       unsigned long flags);

  static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);

  #ifdef CONFIG_RCU_NOCB_CPU

  static void __init rcu_organize_nocb_kthreads(void);

  #define rcu_nocb_lock_irqsave(rdp, flags)				\
  do {									\

  	if (!rcu_segcblist_is_offloaded(&(rdp)->cblist))		\

  		local_irq_save(flags);					\

  	else								\

  		raw_spin_lock_irqsave(&(rdp)->nocb_lock, (flags));	\

  } while (0)
  #else /* #ifdef CONFIG_RCU_NOCB_CPU */
  #define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
  #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */

  static void rcu_bind_gp_kthread(void);

  static bool rcu_nohz_full_cpu(void);

  static void rcu_dynticks_task_enter(void);
  static void rcu_dynticks_task_exit(void);

  static void rcu_dynticks_task_trace_enter(void);
  static void rcu_dynticks_task_trace_exit(void);

  
  /* Forward declarations for tree_stall.h */

  static void record_gp_stall_check_time(void);

  static void rcu_iw_handler(struct irq_work *iwp);

  static void check_cpu_stall(struct rcu_data *rdp);

  static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
  				     const unsigned long gpssdelay);