LXR linux/kernel/rcu/tree.h

   1/* SPDX-License-Identifier: GPL-2.0+ */
   2/*
   3 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
   4 * Internal non-public definitions.
   5 *
   6 * Copyright IBM Corporation, 2008
   7 *
   8 * Author: Ingo Molnar <mingo@elte.hu>
   9 *         Paul E. McKenney <paulmck@linux.ibm.com>
  10 */
  11
  12#include <linux/cache.h>
  13#include <linux/spinlock.h>
  14#include <linux/rtmutex.h>
  15#include <linux/threads.h>
  16#include <linux/cpumask.h>
  17#include <linux/seqlock.h>
  18#include <linux/swait.h>
  19#include <linux/rcu_node_tree.h>
  20
  21#include "rcu_segcblist.h"
  22
  23/* Communicate arguments to a workqueue handler. */
  24struct rcu_exp_work {
  25        unsigned long rew_s;
  26        struct work_struct rew_work;
  27};
  28
  29/* RCU's kthread states for tracing. */
  30#define RCU_KTHREAD_STOPPED  0
  31#define RCU_KTHREAD_RUNNING  1
  32#define RCU_KTHREAD_WAITING  2
  33#define RCU_KTHREAD_OFFCPU   3
  34#define RCU_KTHREAD_YIELDING 4
  35#define RCU_KTHREAD_MAX      4
  36
  37/*
  38 * Definition for node within the RCU grace-period-detection hierarchy.
  39 */
  40struct rcu_node {
  41        raw_spinlock_t __private lock;  /* Root rcu_node's lock protects */
  42                                        /*  some rcu_state fields as well as */
  43                                        /*  following. */
  44        unsigned long gp_seq;   /* Track rsp->gp_seq. */
  45        unsigned long gp_seq_needed; /* Track furthest future GP request. */
  46        unsigned long completedqs; /* All QSes done for this node. */
  47        unsigned long qsmask;   /* CPUs or groups that need to switch in */
  48                                /*  order for current grace period to proceed.*/
  49                                /*  In leaf rcu_node, each bit corresponds to */
  50                                /*  an rcu_data structure, otherwise, each */
  51                                /*  bit corresponds to a child rcu_node */
  52                                /*  structure. */
  53        unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */
  54        unsigned long qsmaskinit;
  55                                /* Per-GP initial value for qsmask. */
  56                                /*  Initialized from ->qsmaskinitnext at the */
  57                                /*  beginning of each grace period. */
  58        unsigned long qsmaskinitnext;
  59        unsigned long ofl_seq;  /* CPU-hotplug operation sequence count. */
  60                                /* Online CPUs for next grace period. */
  61        unsigned long expmask;  /* CPUs or groups that need to check in */
  62                                /*  to allow the current expedited GP */
  63                                /*  to complete. */
  64        unsigned long expmaskinit;
  65                                /* Per-GP initial values for expmask. */
  66                                /*  Initialized from ->expmaskinitnext at the */
  67                                /*  beginning of each expedited GP. */
  68        unsigned long expmaskinitnext;
  69                                /* Online CPUs for next expedited GP. */
  70                                /*  Any CPU that has ever been online will */
  71                                /*  have its bit set. */
  72        unsigned long cbovldmask;
  73                                /* CPUs experiencing callback overload. */
  74        unsigned long ffmask;   /* Fully functional CPUs. */
  75        unsigned long grpmask;  /* Mask to apply to parent qsmask. */
  76                                /*  Only one bit will be set in this mask. */
  77        int     grplo;          /* lowest-numbered CPU here. */
  78        int     grphi;          /* highest-numbered CPU here. */
  79        u8      grpnum;         /* group number for next level up. */
  80        u8      level;          /* root is at level 0. */
  81        bool    wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
  82                                /*  exit RCU read-side critical sections */
  83                                /*  before propagating offline up the */
  84                                /*  rcu_node tree? */
  85        struct rcu_node *parent;
  86        struct list_head blkd_tasks;
  87                                /* Tasks blocked in RCU read-side critical */
  88                                /*  section.  Tasks are placed at the head */
  89                                /*  of this list and age towards the tail. */
  90        struct list_head *gp_tasks;
  91                                /* Pointer to the first task blocking the */
  92                                /*  current grace period, or NULL if there */
  93                                /*  is no such task. */
  94        struct list_head *exp_tasks;
  95                                /* Pointer to the first task blocking the */
  96                                /*  current expedited grace period, or NULL */
  97                                /*  if there is no such task.  If there */
  98                                /*  is no current expedited grace period, */
  99                                /*  then there can cannot be any such task. */
 100        struct list_head *boost_tasks;
 101                                /* Pointer to first task that needs to be */
 102                                /*  priority boosted, or NULL if no priority */
 103                                /*  boosting is needed for this rcu_node */
 104                                /*  structure.  If there are no tasks */
 105                                /*  queued on this rcu_node structure that */
 106                                /*  are blocking the current grace period, */
 107                                /*  there can be no such task. */
 108        struct rt_mutex boost_mtx;
 109                                /* Used only for the priority-boosting */
 110                                /*  side effect, not as a lock. */
 111        unsigned long boost_time;
 112                                /* When to start boosting (jiffies). */
 113        struct task_struct *boost_kthread_task;
 114                                /* kthread that takes care of priority */
 115                                /*  boosting for this rcu_node structure. */
 116        unsigned int boost_kthread_status;
 117                                /* State of boost_kthread_task for tracing. */
 118        unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */
 119#ifdef CONFIG_RCU_NOCB_CPU
 120        struct swait_queue_head nocb_gp_wq[2];
 121                                /* Place for rcu_nocb_kthread() to wait GP. */
 122#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 123        raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
 124
 125        spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
 126        unsigned long exp_seq_rq;
 127        wait_queue_head_t exp_wq[4];
 128        struct rcu_exp_work rew;
 129        bool exp_need_flush;    /* Need to flush workitem? */
 130} ____cacheline_internodealigned_in_smp;
 131
 132/*
 133 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
 134 * are indexed relative to this interval rather than the global CPU ID space.
 135 * This generates the bit for a CPU in node-local masks.
 136 */
 137#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
 138
 139/*
 140 * Union to allow "aggregate OR" operation on the need for a quiescent
 141 * state by the normal and expedited grace periods.
 142 */
 143union rcu_noqs {
 144        struct {
 145                u8 norm;
 146                u8 exp;
 147        } b; /* Bits. */
 148        u16 s; /* Set of bits, aggregate OR here. */
 149};
 150
 151/* Per-CPU data for read-copy update. */
 152struct rcu_data {
 153        /* 1) quiescent-state and grace-period handling : */
 154        unsigned long   gp_seq;         /* Track rsp->gp_seq counter. */
 155        unsigned long   gp_seq_needed;  /* Track furthest future GP request. */
 156        union rcu_noqs  cpu_no_qs;      /* No QSes yet for this CPU. */
 157        bool            core_needs_qs;  /* Core waits for quiescent state. */
 158        bool            beenonline;     /* CPU online at least once. */
 159        bool            gpwrap;         /* Possible ->gp_seq wrap. */
 160        bool            exp_deferred_qs; /* This CPU awaiting a deferred QS? */
 161        bool            cpu_started;    /* RCU watching this onlining CPU. */
 162        struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
 163        unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
 164        unsigned long   ticks_this_gp;  /* The number of scheduling-clock */
 165                                        /*  ticks this CPU has handled */
 166                                        /*  during and after the last grace */
 167                                        /* period it is aware of. */
 168        struct irq_work defer_qs_iw;    /* Obtain later scheduler attention. */
 169        bool defer_qs_iw_pending;       /* Scheduler attention pending? */
 170        struct work_struct strict_work; /* Schedule readers for strict GPs. */
 171
 172        /* 2) batch handling */
 173        struct rcu_segcblist cblist;    /* Segmented callback list, with */
 174                                        /* different callbacks waiting for */
 175                                        /* different grace periods. */
 176        long            qlen_last_fqs_check;
 177                                        /* qlen at last check for QS forcing */
 178        unsigned long   n_cbs_invoked;  /* # callbacks invoked since boot. */
 179        unsigned long   n_force_qs_snap;
 180                                        /* did other CPU force QS recently? */
 181        long            blimit;         /* Upper limit on a processed batch */
 182
 183        /* 3) dynticks interface. */
 184        int dynticks_snap;              /* Per-GP tracking for dynticks. */
 185        long dynticks_nesting;          /* Track process nesting level. */
 186        long dynticks_nmi_nesting;      /* Track irq/NMI nesting level. */
 187        atomic_t dynticks;              /* Even value for idle, else odd. */
 188        bool rcu_need_heavy_qs;         /* GP old, so heavy quiescent state! */
 189        bool rcu_urgent_qs;             /* GP old need light quiescent state. */
 190        bool rcu_forced_tick;           /* Forced tick to provide QS. */
 191        bool rcu_forced_tick_exp;       /*   ... provide QS to expedited GP. */
 192#ifdef CONFIG_RCU_FAST_NO_HZ
 193        unsigned long last_accelerate;  /* Last jiffy CBs were accelerated. */
 194        unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */
 195        int tick_nohz_enabled_snap;     /* Previously seen value from sysfs. */
 196#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 197
 198        /* 4) rcu_barrier(), OOM callbacks, and expediting. */
 199        struct rcu_head barrier_head;
 200        int exp_dynticks_snap;          /* Double-check need for IPI. */
 201
 202        /* 5) Callback offloading. */
 203#ifdef CONFIG_RCU_NOCB_CPU
 204        struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
 205        struct swait_queue_head nocb_state_wq; /* For offloading state changes */
 206        struct task_struct *nocb_gp_kthread;
 207        raw_spinlock_t nocb_lock;       /* Guard following pair of fields. */
 208        atomic_t nocb_lock_contended;   /* Contention experienced. */
 209        int nocb_defer_wakeup;          /* Defer wakeup of nocb_kthread. */
 210        struct timer_list nocb_timer;   /* Enforce finite deferral. */
 211        unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
 212
 213        /* The following fields are used by call_rcu, hence own cacheline. */
 214        raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
 215        struct rcu_cblist nocb_bypass;  /* Lock-contention-bypass CB list. */
 216        unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
 217        unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
 218        int nocb_nobypass_count;        /* # ->cblist enqueues at ^^^ time. */
 219
 220        /* The following fields are used by GP kthread, hence own cacheline. */
 221        raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
 222        u8 nocb_gp_sleep;               /* Is the nocb GP thread asleep? */
 223        u8 nocb_gp_bypass;              /* Found a bypass on last scan? */
 224        u8 nocb_gp_gp;                  /* GP to wait for on last scan? */
 225        unsigned long nocb_gp_seq;      /*  If so, ->gp_seq to wait for. */
 226        unsigned long nocb_gp_loops;    /* # passes through wait code. */
 227        struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
 228        bool nocb_cb_sleep;             /* Is the nocb CB thread asleep? */
 229        struct task_struct *nocb_cb_kthread;
 230        struct rcu_data *nocb_next_cb_rdp;
 231                                        /* Next rcu_data in wakeup chain. */
 232
 233        /* The following fields are used by CB kthread, hence new cacheline. */
 234        struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
 235                                        /* GP rdp takes GP-end wakeups. */
 236#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 237
 238        /* 6) RCU priority boosting. */
 239        struct task_struct *rcu_cpu_kthread_task;
 240                                        /* rcuc per-CPU kthread or NULL. */
 241        unsigned int rcu_cpu_kthread_status;
 242        char rcu_cpu_has_work;
 243
 244        /* 7) Diagnostic data, including RCU CPU stall warnings. */
 245        unsigned int softirq_snap;      /* Snapshot of softirq activity. */
 246        /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
 247        struct irq_work rcu_iw;         /* Check for non-irq activity. */
 248        bool rcu_iw_pending;            /* Is ->rcu_iw pending? */
 249        unsigned long rcu_iw_gp_seq;    /* ->gp_seq associated with ->rcu_iw. */
 250        unsigned long rcu_ofl_gp_seq;   /* ->gp_seq at last offline. */
 251        short rcu_ofl_gp_flags;         /* ->gp_flags at last offline. */
 252        unsigned long rcu_onl_gp_seq;   /* ->gp_seq at last online. */
 253        short rcu_onl_gp_flags;         /* ->gp_flags at last online. */
 254        unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
 255
 256        int cpu;
 257};
 258
 259/* Values for nocb_defer_wakeup field in struct rcu_data. */
 260#define RCU_NOCB_WAKE_NOT       0
 261#define RCU_NOCB_WAKE_BYPASS    1
 262#define RCU_NOCB_WAKE           2
 263#define RCU_NOCB_WAKE_FORCE     3
 264
 265#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
 266                                        /* For jiffies_till_first_fqs and */
 267                                        /*  and jiffies_till_next_fqs. */
 268
 269#define RCU_JIFFIES_FQS_DIV     256     /* Very large systems need more */
 270                                        /*  delay between bouts of */
 271                                        /*  quiescent-state forcing. */
 272
 273#define RCU_STALL_RAT_DELAY     2       /* Allow other CPUs time to take */
 274                                        /*  at least one scheduling clock */
 275                                        /*  irq before ratting on them. */
 276
 277#define rcu_wait(cond)                                                  \
 278do {                                                                    \
 279        for (;;) {                                                      \
 280                set_current_state(TASK_INTERRUPTIBLE);                  \
 281                if (cond)                                               \
 282                        break;                                          \
 283                schedule();                                             \
 284        }                                                               \
 285        __set_current_state(TASK_RUNNING);                              \
 286} while (0)
 287
 288/*
 289 * RCU global state, including node hierarchy.  This hierarchy is
 290 * represented in "heap" form in a dense array.  The root (first level)
 291 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
 292 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
 293 * and the third level in ->node[m+1] and following (->node[m+1] referenced
 294 * by ->level[2]).  The number of levels is determined by the number of
 295 * CPUs and by CONFIG_RCU_FANOUT.  Small systems will have a "hierarchy"
 296 * consisting of a single rcu_node.
 297 */
 298struct rcu_state {
 299        struct rcu_node node[NUM_RCU_NODES];    /* Hierarchy. */
 300        struct rcu_node *level[RCU_NUM_LVLS + 1];
 301                                                /* Hierarchy levels (+1 to */
 302                                                /*  shut bogus gcc warning) */
 303        int ncpus;                              /* # CPUs seen so far. */
 304        int n_online_cpus;                      /* # CPUs online for RCU. */
 305
 306        /* The following fields are guarded by the root rcu_node's lock. */
 307
 308        u8      boost ____cacheline_internodealigned_in_smp;
 309                                                /* Subject to priority boost. */
 310        unsigned long gp_seq;                   /* Grace-period sequence #. */
 311        unsigned long gp_max;                   /* Maximum GP duration in */
 312                                                /*  jiffies. */
 313        struct task_struct *gp_kthread;         /* Task for grace periods. */
 314        struct swait_queue_head gp_wq;          /* Where GP task waits. */
 315        short gp_flags;                         /* Commands for GP task. */
 316        short gp_state;                         /* GP kthread sleep state. */
 317        unsigned long gp_wake_time;             /* Last GP kthread wake. */
 318        unsigned long gp_wake_seq;              /* ->gp_seq at ^^^. */
 319
 320        /* End of fields guarded by root rcu_node's lock. */
 321
 322        struct mutex barrier_mutex;             /* Guards barrier fields. */
 323        atomic_t barrier_cpu_count;             /* # CPUs waiting on. */
 324        struct completion barrier_completion;   /* Wake at barrier end. */
 325        unsigned long barrier_sequence;         /* ++ at start and end of */
 326                                                /*  rcu_barrier(). */
 327        /* End of fields guarded by barrier_mutex. */
 328
 329        struct mutex exp_mutex;                 /* Serialize expedited GP. */
 330        struct mutex exp_wake_mutex;            /* Serialize wakeup. */
 331        unsigned long expedited_sequence;       /* Take a ticket. */
 332        atomic_t expedited_need_qs;             /* # CPUs left to check in. */
 333        struct swait_queue_head expedited_wq;   /* Wait for check-ins. */
 334        int ncpus_snap;                         /* # CPUs seen last time. */
 335        u8 cbovld;                              /* Callback overload now? */
 336        u8 cbovldnext;                          /* ^        ^  next time? */
 337
 338        unsigned long jiffies_force_qs;         /* Time at which to invoke */
 339                                                /*  force_quiescent_state(). */
 340        unsigned long jiffies_kick_kthreads;    /* Time at which to kick */
 341                                                /*  kthreads, if configured. */
 342        unsigned long n_force_qs;               /* Number of calls to */
 343                                                /*  force_quiescent_state(). */
 344        unsigned long gp_start;                 /* Time at which GP started, */
 345                                                /*  but in jiffies. */
 346        unsigned long gp_end;                   /* Time last GP ended, again */
 347                                                /*  in jiffies. */
 348        unsigned long gp_activity;              /* Time of last GP kthread */
 349                                                /*  activity in jiffies. */
 350        unsigned long gp_req_activity;          /* Time of last GP request */
 351                                                /*  in jiffies. */
 352        unsigned long jiffies_stall;            /* Time at which to check */
 353                                                /*  for CPU stalls. */
 354        unsigned long jiffies_resched;          /* Time at which to resched */
 355                                                /*  a reluctant CPU. */
 356        unsigned long n_force_qs_gpstart;       /* Snapshot of n_force_qs at */
 357                                                /*  GP start. */
 358        const char *name;                       /* Name of structure. */
 359        char abbr;                              /* Abbreviated name. */
 360
 361        raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
 362                                                /* Synchronize offline with */
 363                                                /*  GP pre-initialization. */
 364};
 365
 366/* Values for rcu_state structure's gp_flags field. */
 367#define RCU_GP_FLAG_INIT 0x1    /* Need grace-period initialization. */
 368#define RCU_GP_FLAG_FQS  0x2    /* Need grace-period quiescent-state forcing. */
 369#define RCU_GP_FLAG_OVLD 0x4    /* Experiencing callback overload. */
 370
 371/* Values for rcu_state structure's gp_state field. */
 372#define RCU_GP_IDLE      0      /* Initial state and no GP in progress. */
 373#define RCU_GP_WAIT_GPS  1      /* Wait for grace-period start. */
 374#define RCU_GP_DONE_GPS  2      /* Wait done for grace-period start. */
 375#define RCU_GP_ONOFF     3      /* Grace-period initialization hotplug. */
 376#define RCU_GP_INIT      4      /* Grace-period initialization. */
 377#define RCU_GP_WAIT_FQS  5      /* Wait for force-quiescent-state time. */
 378#define RCU_GP_DOING_FQS 6      /* Wait done for force-quiescent-state time. */
 379#define RCU_GP_CLEANUP   7      /* Grace-period cleanup started. */
 380#define RCU_GP_CLEANED   8      /* Grace-period cleanup complete. */
 381
 382/*
 383 * In order to export the rcu_state name to the tracing tools, it
 384 * needs to be added in the __tracepoint_string section.
 385 * This requires defining a separate variable tp_<sname>_varname
 386 * that points to the string being used, and this will allow
 387 * the tracing userspace tools to be able to decipher the string
 388 * address to the matching string.
 389 */
 390#ifdef CONFIG_PREEMPT_RCU
 391#define RCU_ABBR 'p'
 392#define RCU_NAME_RAW "rcu_preempt"
 393#else /* #ifdef CONFIG_PREEMPT_RCU */
 394#define RCU_ABBR 's'
 395#define RCU_NAME_RAW "rcu_sched"
 396#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
 397#ifndef CONFIG_TRACING
 398#define RCU_NAME RCU_NAME_RAW
 399#else /* #ifdef CONFIG_TRACING */
 400static char rcu_name[] = RCU_NAME_RAW;
 401static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
 402#define RCU_NAME rcu_name
 403#endif /* #else #ifdef CONFIG_TRACING */
 404
 405/* Forward declarations for tree_plugin.h */
 406static void rcu_bootup_announce(void);
 407static void rcu_qs(void);
 408static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 409#ifdef CONFIG_HOTPLUG_CPU
 410static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 411#endif /* #ifdef CONFIG_HOTPLUG_CPU */
 412static int rcu_print_task_exp_stall(struct rcu_node *rnp);
 413static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
 414static void rcu_flavor_sched_clock_irq(int user);
 415static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
 416static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 417static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
 418static bool rcu_is_callbacks_kthread(void);
 419static void rcu_cpu_kthread_setup(unsigned int cpu);
 420static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
 421static void __init rcu_spawn_boost_kthreads(void);
 422static void rcu_cleanup_after_idle(void);
 423static void rcu_prepare_for_idle(void);
 424static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 425static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
 426static void rcu_preempt_deferred_qs(struct task_struct *t);
 427static void zero_cpu_stall_ticks(struct rcu_data *rdp);
 428static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
 429static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
 430static void rcu_init_one_nocb(struct rcu_node *rnp);
 431static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
 432                                  unsigned long j);
 433static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
 434                                bool *was_alldone, unsigned long flags);
 435static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
 436                                 unsigned long flags);
 437static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
 438static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
 439static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
 440static void rcu_spawn_cpu_nocb_kthread(int cpu);
 441static void __init rcu_spawn_nocb_kthreads(void);
 442static void show_rcu_nocb_state(struct rcu_data *rdp);
 443static void rcu_nocb_lock(struct rcu_data *rdp);
 444static void rcu_nocb_unlock(struct rcu_data *rdp);
 445static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
 446                                       unsigned long flags);
 447static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
 448#ifdef CONFIG_RCU_NOCB_CPU
 449static void __init rcu_organize_nocb_kthreads(void);
 450#define rcu_nocb_lock_irqsave(rdp, flags)                               \
 451do {                                                                    \
 452        if (!rcu_segcblist_is_offloaded(&(rdp)->cblist))                \
 453                local_irq_save(flags);                                  \
 454        else                                                            \
 455                raw_spin_lock_irqsave(&(rdp)->nocb_lock, (flags));      \
 456} while (0)
 457#else /* #ifdef CONFIG_RCU_NOCB_CPU */
 458#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
 459#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
 460
 461static void rcu_bind_gp_kthread(void);
 462static bool rcu_nohz_full_cpu(void);
 463static void rcu_dynticks_task_enter(void);
 464static void rcu_dynticks_task_exit(void);
 465static void rcu_dynticks_task_trace_enter(void);
 466static void rcu_dynticks_task_trace_exit(void);
 467
 468/* Forward declarations for tree_stall.h */
 469static void record_gp_stall_check_time(void);
 470static void rcu_iw_handler(struct irq_work *iwp);
 471static void check_cpu_stall(struct rcu_data *rdp);
 472static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
 473                                     const unsigned long gpssdelay);
 474