122e40925SPaul E. McKenney /* SPDX-License-Identifier: GPL-2.0+ */ 24102adabSPaul E. McKenney /* 34102adabSPaul E. McKenney * Read-Copy Update mechanism for mutual exclusion (tree-based version) 44102adabSPaul E. McKenney * Internal non-public definitions. 54102adabSPaul E. McKenney * 64102adabSPaul E. McKenney * Copyright IBM Corporation, 2008 74102adabSPaul E. McKenney * 84102adabSPaul E. McKenney * Author: Ingo Molnar <mingo@elte.hu> 922e40925SPaul E. McKenney * Paul E. McKenney <paulmck@linux.ibm.com> 104102adabSPaul E. McKenney */ 114102adabSPaul E. McKenney 124102adabSPaul E. McKenney #include <linux/cache.h> 139621fbeeSKalesh Singh #include <linux/kthread.h> 144102adabSPaul E. McKenney #include <linux/spinlock.h> 15037741a6SIngo Molnar #include <linux/rtmutex.h> 164102adabSPaul E. McKenney #include <linux/threads.h> 174102adabSPaul E. McKenney #include <linux/cpumask.h> 184102adabSPaul E. McKenney #include <linux/seqlock.h> 19abedf8e2SPaul Gortmaker #include <linux/swait.h> 20f2425b4eSPaul E. McKenney #include <linux/rcu_node_tree.h> 214102adabSPaul E. McKenney 2245753c5fSIngo Molnar #include "rcu_segcblist.h" 2345753c5fSIngo Molnar 2425f3d7efSPaul E. McKenney /* Communicate arguments to a workqueue handler. */ 2525f3d7efSPaul E. McKenney struct rcu_exp_work { 2625f3d7efSPaul E. McKenney unsigned long rew_s; 279621fbeeSKalesh Singh #ifdef CONFIG_RCU_EXP_KTHREAD 289621fbeeSKalesh Singh struct kthread_work rew_work; 299621fbeeSKalesh Singh #else 3025f3d7efSPaul E. McKenney struct work_struct rew_work; 319621fbeeSKalesh Singh #endif /* CONFIG_RCU_EXP_KTHREAD */ 3225f3d7efSPaul E. McKenney }; 3325f3d7efSPaul E. McKenney 344102adabSPaul E. McKenney /* RCU's kthread states for tracing. */ 354102adabSPaul E. McKenney #define RCU_KTHREAD_STOPPED 0 364102adabSPaul E. McKenney #define RCU_KTHREAD_RUNNING 1 374102adabSPaul E. McKenney #define RCU_KTHREAD_WAITING 2 384102adabSPaul E. McKenney #define RCU_KTHREAD_OFFCPU 3 394102adabSPaul E. McKenney #define RCU_KTHREAD_YIELDING 4 404102adabSPaul E. McKenney #define RCU_KTHREAD_MAX 4 414102adabSPaul E. McKenney 424102adabSPaul E. McKenney /* 434102adabSPaul E. McKenney * Definition for node within the RCU grace-period-detection hierarchy. 444102adabSPaul E. McKenney */ 454102adabSPaul E. McKenney struct rcu_node { 4667c583a7SBoqun Feng raw_spinlock_t __private lock; /* Root rcu_node's lock protects */ 4767c583a7SBoqun Feng /* some rcu_state fields as well as */ 4867c583a7SBoqun Feng /* following. */ 49360fbbb4SLihao Liang unsigned long gp_seq; /* Track rsp->gp_seq. */ 50adbccddbSJoel Fernandes (Google) unsigned long gp_seq_needed; /* Track furthest future GP request. */ 514bc8d555SPaul E. McKenney unsigned long completedqs; /* All QSes done for this node. */ 524102adabSPaul E. McKenney unsigned long qsmask; /* CPUs or groups that need to switch in */ 534102adabSPaul E. McKenney /* order for current grace period to proceed.*/ 544102adabSPaul E. McKenney /* In leaf rcu_node, each bit corresponds to */ 554102adabSPaul E. McKenney /* an rcu_data structure, otherwise, each */ 564102adabSPaul E. McKenney /* bit corresponds to a child rcu_node */ 574102adabSPaul E. McKenney /* structure. */ 58f2e2df59SPaul E. McKenney unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */ 594102adabSPaul E. McKenney unsigned long qsmaskinit; 60b9585e94SPaul E. McKenney /* Per-GP initial value for qsmask. */ 610aa04b05SPaul E. McKenney /* Initialized from ->qsmaskinitnext at the */ 620aa04b05SPaul E. McKenney /* beginning of each grace period. */ 630aa04b05SPaul E. McKenney unsigned long qsmaskinitnext; 64b9585e94SPaul E. McKenney unsigned long expmask; /* CPUs or groups that need to check in */ 65b9585e94SPaul E. McKenney /* to allow the current expedited GP */ 66b9585e94SPaul E. McKenney /* to complete. */ 67b9585e94SPaul E. McKenney unsigned long expmaskinit; 68b9585e94SPaul E. McKenney /* Per-GP initial values for expmask. */ 69b9585e94SPaul E. McKenney /* Initialized from ->expmaskinitnext at the */ 70b9585e94SPaul E. McKenney /* beginning of each expedited GP. */ 71b9585e94SPaul E. McKenney unsigned long expmaskinitnext; 72b9585e94SPaul E. McKenney /* Online CPUs for next expedited GP. */ 731de6e56dSPaul E. McKenney /* Any CPU that has ever been online will */ 741de6e56dSPaul E. McKenney /* have its bit set. */ 75b2b00ddfSPaul E. McKenney unsigned long cbovldmask; 76b2b00ddfSPaul E. McKenney /* CPUs experiencing callback overload. */ 779b9500daSPaul E. McKenney unsigned long ffmask; /* Fully functional CPUs. */ 784102adabSPaul E. McKenney unsigned long grpmask; /* Mask to apply to parent qsmask. */ 794102adabSPaul E. McKenney /* Only one bit will be set in this mask. */ 80a2dae430SWei Yang int grplo; /* lowest-numbered CPU here. */ 81a2dae430SWei Yang int grphi; /* highest-numbered CPU here. */ 827a0c2b09SWei Yang u8 grpnum; /* group number for next level up. */ 834102adabSPaul E. McKenney u8 level; /* root is at level 0. */ 840aa04b05SPaul E. McKenney bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */ 850aa04b05SPaul E. McKenney /* exit RCU read-side critical sections */ 860aa04b05SPaul E. McKenney /* before propagating offline up the */ 870aa04b05SPaul E. McKenney /* rcu_node tree? */ 884102adabSPaul E. McKenney struct rcu_node *parent; 894102adabSPaul E. McKenney struct list_head blkd_tasks; 904102adabSPaul E. McKenney /* Tasks blocked in RCU read-side critical */ 914102adabSPaul E. McKenney /* section. Tasks are placed at the head */ 924102adabSPaul E. McKenney /* of this list and age towards the tail. */ 934102adabSPaul E. McKenney struct list_head *gp_tasks; 944102adabSPaul E. McKenney /* Pointer to the first task blocking the */ 954102adabSPaul E. McKenney /* current grace period, or NULL if there */ 964102adabSPaul E. McKenney /* is no such task. */ 974102adabSPaul E. McKenney struct list_head *exp_tasks; 984102adabSPaul E. McKenney /* Pointer to the first task blocking the */ 994102adabSPaul E. McKenney /* current expedited grace period, or NULL */ 1004102adabSPaul E. McKenney /* if there is no such task. If there */ 1014102adabSPaul E. McKenney /* is no current expedited grace period, */ 1024102adabSPaul E. McKenney /* then there can cannot be any such task. */ 1034102adabSPaul E. McKenney struct list_head *boost_tasks; 1044102adabSPaul E. McKenney /* Pointer to first task that needs to be */ 1054102adabSPaul E. McKenney /* priority boosted, or NULL if no priority */ 1064102adabSPaul E. McKenney /* boosting is needed for this rcu_node */ 1074102adabSPaul E. McKenney /* structure. If there are no tasks */ 1084102adabSPaul E. McKenney /* queued on this rcu_node structure that */ 1094102adabSPaul E. McKenney /* are blocking the current grace period, */ 1104102adabSPaul E. McKenney /* there can be no such task. */ 111abaa93d9SPaul E. McKenney struct rt_mutex boost_mtx; 112abaa93d9SPaul E. McKenney /* Used only for the priority-boosting */ 113abaa93d9SPaul E. McKenney /* side effect, not as a lock. */ 1144102adabSPaul E. McKenney unsigned long boost_time; 1154102adabSPaul E. McKenney /* When to start boosting (jiffies). */ 116218b957aSDavid Woodhouse struct mutex boost_kthread_mutex; 117218b957aSDavid Woodhouse /* Exclusion for thread spawning and affinity */ 118218b957aSDavid Woodhouse /* manipulation. */ 1194102adabSPaul E. McKenney struct task_struct *boost_kthread_task; 1204102adabSPaul E. McKenney /* kthread that takes care of priority */ 1214102adabSPaul E. McKenney /* boosting for this rcu_node structure. */ 1224102adabSPaul E. McKenney unsigned int boost_kthread_status; 1234102adabSPaul E. McKenney /* State of boost_kthread_task for tracing. */ 124396eba65SPaul E. McKenney unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */ 1254102adabSPaul E. McKenney #ifdef CONFIG_RCU_NOCB_CPU 126abedf8e2SPaul Gortmaker struct swait_queue_head nocb_gp_wq[2]; 1274102adabSPaul E. McKenney /* Place for rcu_nocb_kthread() to wait GP. */ 1284102adabSPaul E. McKenney #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 1294102adabSPaul E. McKenney raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp; 130385b73c0SPaul E. McKenney 131f6a12f34SPaul E. McKenney spinlock_t exp_lock ____cacheline_internodealigned_in_smp; 132f6a12f34SPaul E. McKenney unsigned long exp_seq_rq; 1333b5f668eSPaul E. McKenney wait_queue_head_t exp_wq[4]; 13425f3d7efSPaul E. McKenney struct rcu_exp_work rew; 13525f3d7efSPaul E. McKenney bool exp_need_flush; /* Need to flush workitem? */ 136d96c52feSPaul E. McKenney raw_spinlock_t exp_poll_lock; 137d96c52feSPaul E. McKenney /* Lock and data for polled expedited grace periods. */ 138d96c52feSPaul E. McKenney unsigned long exp_seq_poll_rq; 139d96c52feSPaul E. McKenney struct work_struct exp_poll_wq; 1404102adabSPaul E. McKenney } ____cacheline_internodealigned_in_smp; 1414102adabSPaul E. McKenney 1424102adabSPaul E. McKenney /* 143bc75e999SMark Rutland * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and 144bc75e999SMark Rutland * are indexed relative to this interval rather than the global CPU ID space. 145bc75e999SMark Rutland * This generates the bit for a CPU in node-local masks. 146bc75e999SMark Rutland */ 147df63fa5bSPaul E. McKenney #define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo)) 148bc75e999SMark Rutland 149bc75e999SMark Rutland /* 1505b74c458SPaul E. McKenney * Union to allow "aggregate OR" operation on the need for a quiescent 1515b74c458SPaul E. McKenney * state by the normal and expedited grace periods. 1525b74c458SPaul E. McKenney */ 1535b74c458SPaul E. McKenney union rcu_noqs { 1545b74c458SPaul E. McKenney struct { 1555b74c458SPaul E. McKenney u8 norm; 1565b74c458SPaul E. McKenney u8 exp; 1575b74c458SPaul E. McKenney } b; /* Bits. */ 1585b74c458SPaul E. McKenney u16 s; /* Set of bits, aggregate OR here. */ 1595b74c458SPaul E. McKenney }; 1605b74c458SPaul E. McKenney 1614102adabSPaul E. McKenney /* Per-CPU data for read-copy update. */ 1624102adabSPaul E. McKenney struct rcu_data { 1634102adabSPaul E. McKenney /* 1) quiescent-state and grace-period handling : */ 164360fbbb4SLihao Liang unsigned long gp_seq; /* Track rsp->gp_seq counter. */ 165adbccddbSJoel Fernandes (Google) unsigned long gp_seq_needed; /* Track furthest future GP request. */ 1665b74c458SPaul E. McKenney union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */ 167a616aec9SIngo Molnar bool core_needs_qs; /* Core waits for quiescent state. */ 1684102adabSPaul E. McKenney bool beenonline; /* CPU online at least once. */ 169ff3bb6f4SPaul E. McKenney bool gpwrap; /* Possible ->gp_seq wrap. */ 170c0f97f20SPaul E. McKenney bool cpu_started; /* RCU watching this onlining CPU. */ 1714102adabSPaul E. McKenney struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ 1724102adabSPaul E. McKenney unsigned long grpmask; /* Mask to apply to leaf qsmask. */ 1734102adabSPaul E. McKenney unsigned long ticks_this_gp; /* The number of scheduling-clock */ 1744102adabSPaul E. McKenney /* ticks this CPU has handled */ 1754102adabSPaul E. McKenney /* during and after the last grace */ 1764102adabSPaul E. McKenney /* period it is aware of. */ 1770864f057SPaul E. McKenney struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */ 1780864f057SPaul E. McKenney bool defer_qs_iw_pending; /* Scheduler attention pending? */ 179a657f261SPaul E. McKenney struct work_struct strict_work; /* Schedule readers for strict GPs. */ 1804102adabSPaul E. McKenney 1814102adabSPaul E. McKenney /* 2) batch handling */ 18215fecf89SPaul E. McKenney struct rcu_segcblist cblist; /* Segmented callback list, with */ 18315fecf89SPaul E. McKenney /* different callbacks waiting for */ 18415fecf89SPaul E. McKenney /* different grace periods. */ 1854102adabSPaul E. McKenney long qlen_last_fqs_check; 1864102adabSPaul E. McKenney /* qlen at last check for QS forcing */ 187e816d56fSPaul E. McKenney unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */ 1884102adabSPaul E. McKenney unsigned long n_force_qs_snap; 1894102adabSPaul E. McKenney /* did other CPU force QS recently? */ 1904102adabSPaul E. McKenney long blimit; /* Upper limit on a processed batch */ 1914102adabSPaul E. McKenney 1924102adabSPaul E. McKenney /* 3) dynticks interface. */ 1934102adabSPaul E. McKenney int dynticks_snap; /* Per-GP tracking for dynticks. */ 194dc5a4f29SPaul E. McKenney bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */ 195cc72046cSPaul E. McKenney bool rcu_urgent_qs; /* GP old need light quiescent state. */ 19666e4c33bSPaul E. McKenney bool rcu_forced_tick; /* Forced tick to provide QS. */ 197df1e849aSPaul E. McKenney bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */ 1984102adabSPaul E. McKenney 1998d8a9d0eSPaul E. McKenney /* 4) rcu_barrier(), OOM callbacks, and expediting. */ 200a16578ddSPaul E. McKenney unsigned long barrier_seq_snap; /* Snap of rcu_state.barrier_sequence. */ 2014102adabSPaul E. McKenney struct rcu_head barrier_head; 2020742ac3eSPaul E. McKenney int exp_dynticks_snap; /* Double-check need for IPI. */ 2034102adabSPaul E. McKenney 2048d8a9d0eSPaul E. McKenney /* 5) Callback offloading. */ 2054102adabSPaul E. McKenney #ifdef CONFIG_RCU_NOCB_CPU 20612f54c3aSPaul E. McKenney struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */ 207d97b0781SFrederic Weisbecker struct swait_queue_head nocb_state_wq; /* For offloading state changes */ 20812f54c3aSPaul E. McKenney struct task_struct *nocb_gp_kthread; 2098be6e1b1SPaul E. McKenney raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ 21081c0b3d7SPaul E. McKenney atomic_t nocb_lock_contended; /* Contention experienced. */ 2119fdd3bc9SPaul E. McKenney int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ 2128be6e1b1SPaul E. McKenney struct timer_list nocb_timer; /* Enforce finite deferral. */ 213d1b222c6SPaul E. McKenney unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */ 21402e30241SNeeraj Upadhyay struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */ 21502e30241SNeeraj Upadhyay /* spawning */ 216d1b222c6SPaul E. McKenney 217d1b222c6SPaul E. McKenney /* The following fields are used by call_rcu, hence own cacheline. */ 218d1b222c6SPaul E. McKenney raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp; 219d1b222c6SPaul E. McKenney struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */ 220d1b222c6SPaul E. McKenney unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */ 221d1b222c6SPaul E. McKenney unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */ 222d1b222c6SPaul E. McKenney int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */ 223fbce7497SPaul E. McKenney 2246484fe54SPaul E. McKenney /* The following fields are used by GP kthread, hence own cacheline. */ 2254fd8c5f1SPaul E. McKenney raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp; 226f7a81b12SPaul E. McKenney u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */ 227f7a81b12SPaul E. McKenney u8 nocb_gp_bypass; /* Found a bypass on last scan? */ 228f7a81b12SPaul E. McKenney u8 nocb_gp_gp; /* GP to wait for on last scan? */ 229f7a81b12SPaul E. McKenney unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */ 230f7a81b12SPaul E. McKenney unsigned long nocb_gp_loops; /* # passes through wait code. */ 23112f54c3aSPaul E. McKenney struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */ 2325d6742b3SPaul E. McKenney bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */ 23312f54c3aSPaul E. McKenney struct task_struct *nocb_cb_kthread; 2342ebc45c4SFrederic Weisbecker struct list_head nocb_head_rdp; /* 2352ebc45c4SFrederic Weisbecker * Head of rcu_data list in wakeup chain, 2362ebc45c4SFrederic Weisbecker * if rdp_gp. 2372ebc45c4SFrederic Weisbecker */ 2382ebc45c4SFrederic Weisbecker struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */ 2391598f4a4SFrederic Weisbecker struct rcu_data *nocb_toggling_rdp; /* rdp queued for (de-)offloading */ 240fbce7497SPaul E. McKenney 241d1b222c6SPaul E. McKenney /* The following fields are used by CB kthread, hence new cacheline. */ 24258bf6f77SPaul E. McKenney struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp; 2436484fe54SPaul E. McKenney /* GP rdp takes GP-end wakeups. */ 2444102adabSPaul E. McKenney #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 2454102adabSPaul E. McKenney 24637f62d7cSPaul E. McKenney /* 6) RCU priority boosting. */ 24737f62d7cSPaul E. McKenney struct task_struct *rcu_cpu_kthread_task; 24837f62d7cSPaul E. McKenney /* rcuc per-CPU kthread or NULL. */ 2496ffdde28SPaul E. McKenney unsigned int rcu_cpu_kthread_status; 250f7e972eeSPaul E. McKenney char rcu_cpu_has_work; 251c9515875SZqiang unsigned long rcuc_activity; 25237f62d7cSPaul E. McKenney 25337f62d7cSPaul E. McKenney /* 7) Diagnostic data, including RCU CPU stall warnings. */ 2544102adabSPaul E. McKenney unsigned int softirq_snap; /* Snapshot of softirq activity. */ 2559b9500daSPaul E. McKenney /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */ 2569b9500daSPaul E. McKenney struct irq_work rcu_iw; /* Check for non-irq activity. */ 2579b9500daSPaul E. McKenney bool rcu_iw_pending; /* Is ->rcu_iw pending? */ 2588aa670cdSPaul E. McKenney unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ 25957738942SPaul E. McKenney unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ 26057738942SPaul E. McKenney short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */ 26157738942SPaul E. McKenney unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ 26257738942SPaul E. McKenney short rcu_onl_gp_flags; /* ->gp_flags at last online. */ 263d3052109SPaul E. McKenney unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ 264c708b08cSPaul E. McKenney unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */ 2654102adabSPaul E. McKenney 2664102adabSPaul E. McKenney int cpu; 2674102adabSPaul E. McKenney }; 2684102adabSPaul E. McKenney 2699fdd3bc9SPaul E. McKenney /* Values for nocb_defer_wakeup field in struct rcu_data. */ 270511324e4SPaul E. McKenney #define RCU_NOCB_WAKE_NOT 0 271e75bcd48SFrederic Weisbecker #define RCU_NOCB_WAKE_BYPASS 1 272e75bcd48SFrederic Weisbecker #define RCU_NOCB_WAKE 2 273e75bcd48SFrederic Weisbecker #define RCU_NOCB_WAKE_FORCE 3 2749fdd3bc9SPaul E. McKenney 2754102adabSPaul E. McKenney #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) 2764102adabSPaul E. McKenney /* For jiffies_till_first_fqs and */ 2774102adabSPaul E. McKenney /* and jiffies_till_next_fqs. */ 2784102adabSPaul E. McKenney 2794102adabSPaul E. McKenney #define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */ 2804102adabSPaul E. McKenney /* delay between bouts of */ 2814102adabSPaul E. McKenney /* quiescent-state forcing. */ 2824102adabSPaul E. McKenney 2834102adabSPaul E. McKenney #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */ 2844102adabSPaul E. McKenney /* at least one scheduling clock */ 2854102adabSPaul E. McKenney /* irq before ratting on them. */ 2864102adabSPaul E. McKenney 2874102adabSPaul E. McKenney #define rcu_wait(cond) \ 2884102adabSPaul E. McKenney do { \ 2894102adabSPaul E. McKenney for (;;) { \ 2904102adabSPaul E. McKenney set_current_state(TASK_INTERRUPTIBLE); \ 2914102adabSPaul E. McKenney if (cond) \ 2924102adabSPaul E. McKenney break; \ 2934102adabSPaul E. McKenney schedule(); \ 2944102adabSPaul E. McKenney } \ 2954102adabSPaul E. McKenney __set_current_state(TASK_RUNNING); \ 2964102adabSPaul E. McKenney } while (0) 2974102adabSPaul E. McKenney 2984102adabSPaul E. McKenney /* 2994102adabSPaul E. McKenney * RCU global state, including node hierarchy. This hierarchy is 3004102adabSPaul E. McKenney * represented in "heap" form in a dense array. The root (first level) 3014102adabSPaul E. McKenney * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second 3024102adabSPaul E. McKenney * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), 3034102adabSPaul E. McKenney * and the third level in ->node[m+1] and following (->node[m+1] referenced 3044102adabSPaul E. McKenney * by ->level[2]). The number of levels is determined by the number of 3054102adabSPaul E. McKenney * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" 3064102adabSPaul E. McKenney * consisting of a single rcu_node. 3074102adabSPaul E. McKenney */ 3084102adabSPaul E. McKenney struct rcu_state { 3094102adabSPaul E. McKenney struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ 310032dfc87SAlexander Gordeev struct rcu_node *level[RCU_NUM_LVLS + 1]; 311032dfc87SAlexander Gordeev /* Hierarchy levels (+1 to */ 312032dfc87SAlexander Gordeev /* shut bogus gcc warning) */ 313b9585e94SPaul E. McKenney int ncpus; /* # CPUs seen so far. */ 314ed73860cSNeeraj Upadhyay int n_online_cpus; /* # CPUs online for RCU. */ 3154102adabSPaul E. McKenney 3164102adabSPaul E. McKenney /* The following fields are guarded by the root rcu_node's lock. */ 3174102adabSPaul E. McKenney 318eae9f147SNeeraj Upadhyay unsigned long gp_seq ____cacheline_internodealigned_in_smp; 319eae9f147SNeeraj Upadhyay /* Grace-period sequence #. */ 32000943a60SWei Yang unsigned long gp_max; /* Maximum GP duration in */ 32100943a60SWei Yang /* jiffies. */ 3224102adabSPaul E. McKenney struct task_struct *gp_kthread; /* Task for grace periods. */ 323abedf8e2SPaul Gortmaker struct swait_queue_head gp_wq; /* Where GP task waits. */ 324afea227fSPaul E. McKenney short gp_flags; /* Commands for GP task. */ 325afea227fSPaul E. McKenney short gp_state; /* GP kthread sleep state. */ 326fd897573SPaul E. McKenney unsigned long gp_wake_time; /* Last GP kthread wake. */ 327fd897573SPaul E. McKenney unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */ 328bf95b2bcSPaul E. McKenney unsigned long gp_seq_polled; /* GP seq for polled API. */ 329bf95b2bcSPaul E. McKenney unsigned long gp_seq_polled_snap; /* ->gp_seq_polled at normal GP start. */ 330dd041405SPaul E. McKenney unsigned long gp_seq_polled_exp_snap; /* ->gp_seq_polled at expedited GP start. */ 3314102adabSPaul E. McKenney 3324102adabSPaul E. McKenney /* End of fields guarded by root rcu_node's lock. */ 3334102adabSPaul E. McKenney 3344102adabSPaul E. McKenney struct mutex barrier_mutex; /* Guards barrier fields. */ 3354102adabSPaul E. McKenney atomic_t barrier_cpu_count; /* # CPUs waiting on. */ 3364102adabSPaul E. McKenney struct completion barrier_completion; /* Wake at barrier end. */ 3374f525a52SPaul E. McKenney unsigned long barrier_sequence; /* ++ at start and end of */ 338dd46a788SPaul E. McKenney /* rcu_barrier(). */ 3394102adabSPaul E. McKenney /* End of fields guarded by barrier_mutex. */ 3404102adabSPaul E. McKenney 34180b3fd47SPaul E. McKenney raw_spinlock_t barrier_lock; /* Protects ->barrier_seq_snap. */ 34280b3fd47SPaul E. McKenney 343f6a12f34SPaul E. McKenney struct mutex exp_mutex; /* Serialize expedited GP. */ 3443b5f668eSPaul E. McKenney struct mutex exp_wake_mutex; /* Serialize wakeup. */ 345d6ada2cfSPaul E. McKenney unsigned long expedited_sequence; /* Take a ticket. */ 3463a6d7c64SPeter Zijlstra atomic_t expedited_need_qs; /* # CPUs left to check in. */ 347abedf8e2SPaul Gortmaker struct swait_queue_head expedited_wq; /* Wait for check-ins. */ 348b9585e94SPaul E. McKenney int ncpus_snap; /* # CPUs seen last time. */ 349b2b00ddfSPaul E. McKenney u8 cbovld; /* Callback overload now? */ 350b2b00ddfSPaul E. McKenney u8 cbovldnext; /* ^ ^ next time? */ 3514102adabSPaul E. McKenney 3524102adabSPaul E. McKenney unsigned long jiffies_force_qs; /* Time at which to invoke */ 3534102adabSPaul E. McKenney /* force_quiescent_state(). */ 3548c7c4829SPaul E. McKenney unsigned long jiffies_kick_kthreads; /* Time at which to kick */ 3558c7c4829SPaul E. McKenney /* kthreads, if configured. */ 3564102adabSPaul E. McKenney unsigned long n_force_qs; /* Number of calls to */ 3574102adabSPaul E. McKenney /* force_quiescent_state(). */ 3584102adabSPaul E. McKenney unsigned long gp_start; /* Time at which GP started, */ 3594102adabSPaul E. McKenney /* but in jiffies. */ 360c51d7b5eSPaul E. McKenney unsigned long gp_end; /* Time last GP ended, again */ 361c51d7b5eSPaul E. McKenney /* in jiffies. */ 3626ccd2ecdSPaul E. McKenney unsigned long gp_activity; /* Time of last GP kthread */ 3636ccd2ecdSPaul E. McKenney /* activity in jiffies. */ 36426d950a9SPaul E. McKenney unsigned long gp_req_activity; /* Time of last GP request */ 36526d950a9SPaul E. McKenney /* in jiffies. */ 3664102adabSPaul E. McKenney unsigned long jiffies_stall; /* Time at which to check */ 3674102adabSPaul E. McKenney /* for CPU stalls. */ 3686193c76aSPaul E. McKenney unsigned long jiffies_resched; /* Time at which to resched */ 3696193c76aSPaul E. McKenney /* a reluctant CPU. */ 370fc908ed3SPaul E. McKenney unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */ 371fc908ed3SPaul E. McKenney /* GP start. */ 3724102adabSPaul E. McKenney const char *name; /* Name of structure. */ 3734102adabSPaul E. McKenney char abbr; /* Abbreviated name. */ 3741e64b15aSPaul E. McKenney 37582980b16SDavid Woodhouse arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp; 3761e64b15aSPaul E. McKenney /* Synchronize offline with */ 3771e64b15aSPaul E. McKenney /* GP pre-initialization. */ 3788d2aaa9bSFrederic Weisbecker int nocb_is_setup; /* nocb is setup from boot */ 3794102adabSPaul E. McKenney }; 3804102adabSPaul E. McKenney 3814102adabSPaul E. McKenney /* Values for rcu_state structure's gp_flags field. */ 3824102adabSPaul E. McKenney #define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */ 3834102adabSPaul E. McKenney #define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */ 3841fca4d12SPaul E. McKenney #define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */ 3854102adabSPaul E. McKenney 386c34d2f41SPaul E. McKenney /* Values for rcu_state structure's gp_state field. */ 38777f81fe0SPetr Mladek #define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */ 388afea227fSPaul E. McKenney #define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */ 389319362c9SPaul E. McKenney #define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */ 390fea3f222SPaul E. McKenney #define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */ 391fea3f222SPaul E. McKenney #define RCU_GP_INIT 4 /* Grace-period initialization. */ 392fea3f222SPaul E. McKenney #define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */ 393fea3f222SPaul E. McKenney #define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */ 394fea3f222SPaul E. McKenney #define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */ 395fea3f222SPaul E. McKenney #define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */ 396afea227fSPaul E. McKenney 397358be2d3SPaul E. McKenney /* 398358be2d3SPaul E. McKenney * In order to export the rcu_state name to the tracing tools, it 399358be2d3SPaul E. McKenney * needs to be added in the __tracepoint_string section. 400358be2d3SPaul E. McKenney * This requires defining a separate variable tp_<sname>_varname 401358be2d3SPaul E. McKenney * that points to the string being used, and this will allow 402358be2d3SPaul E. McKenney * the tracing userspace tools to be able to decipher the string 403358be2d3SPaul E. McKenney * address to the matching string. 404358be2d3SPaul E. McKenney */ 405358be2d3SPaul E. McKenney #ifdef CONFIG_PREEMPT_RCU 406358be2d3SPaul E. McKenney #define RCU_ABBR 'p' 407358be2d3SPaul E. McKenney #define RCU_NAME_RAW "rcu_preempt" 408358be2d3SPaul E. McKenney #else /* #ifdef CONFIG_PREEMPT_RCU */ 409358be2d3SPaul E. McKenney #define RCU_ABBR 's' 410358be2d3SPaul E. McKenney #define RCU_NAME_RAW "rcu_sched" 411358be2d3SPaul E. McKenney #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ 412358be2d3SPaul E. McKenney #ifndef CONFIG_TRACING 413358be2d3SPaul E. McKenney #define RCU_NAME RCU_NAME_RAW 414358be2d3SPaul E. McKenney #else /* #ifdef CONFIG_TRACING */ 415358be2d3SPaul E. McKenney static char rcu_name[] = RCU_NAME_RAW; 416358be2d3SPaul E. McKenney static const char *tp_rcu_varname __used __tracepoint_string = rcu_name; 417358be2d3SPaul E. McKenney #define RCU_NAME rcu_name 418358be2d3SPaul E. McKenney #endif /* #else #ifdef CONFIG_TRACING */ 4196b50e119SPaul E. McKenney 42032255d51SPaul E. McKenney /* Forward declarations for tree_plugin.h */ 4214102adabSPaul E. McKenney static void rcu_bootup_announce(void); 42245975c7dSPaul E. McKenney static void rcu_qs(void); 4234102adabSPaul E. McKenney static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); 4244102adabSPaul E. McKenney #ifdef CONFIG_HOTPLUG_CPU 4258af3a5e7SPaul E. McKenney static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 4264102adabSPaul E. McKenney #endif /* #ifdef CONFIG_HOTPLUG_CPU */ 42774611ecbSPaul E. McKenney static int rcu_print_task_exp_stall(struct rcu_node *rnp); 42881ab59a3SPaul E. McKenney static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); 429c98cac60SPaul E. McKenney static void rcu_flavor_sched_clock_irq(int user); 43081ab59a3SPaul E. McKenney static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck); 4314102adabSPaul E. McKenney static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); 4324102adabSPaul E. McKenney static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); 43351038506SZqiang static bool rcu_is_callbacks_kthread(struct rcu_data *rdp); 43448d07c04SSebastian Andrzej Siewior static void rcu_cpu_kthread_setup(unsigned int cpu); 4353ef5a1c3SPaul E. McKenney static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp); 4360aa04b05SPaul E. McKenney static bool rcu_preempt_has_tasks(struct rcu_node *rnp); 4373e310098SPaul E. McKenney static bool rcu_preempt_need_deferred_qs(struct task_struct *t); 4384102adabSPaul E. McKenney static void zero_cpu_stall_ticks(struct rcu_data *rdp); 439abedf8e2SPaul Gortmaker static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp); 440abedf8e2SPaul Gortmaker static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq); 4414102adabSPaul E. McKenney static void rcu_init_one_nocb(struct rcu_node *rnp); 442*b8f7aca3SFrederic Weisbecker static bool wake_nocb_gp(struct rcu_data *rdp, bool force); 443d1b222c6SPaul E. McKenney static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, 444d1b222c6SPaul E. McKenney unsigned long j); 445d1b222c6SPaul E. McKenney static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, 446d1b222c6SPaul E. McKenney bool *was_alldone, unsigned long flags); 4475d6742b3SPaul E. McKenney static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, 44896d3fd0dSPaul E. McKenney unsigned long flags); 44987090516SFrederic Weisbecker static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level); 450f8bb5caeSFrederic Weisbecker static bool do_nocb_deferred_wakeup(struct rcu_data *rdp); 4514102adabSPaul E. McKenney static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); 452ad368d15SPaul E. McKenney static void rcu_spawn_cpu_nocb_kthread(int cpu); 453f7a81b12SPaul E. McKenney static void show_rcu_nocb_state(struct rcu_data *rdp); 4545d6742b3SPaul E. McKenney static void rcu_nocb_lock(struct rcu_data *rdp); 4555d6742b3SPaul E. McKenney static void rcu_nocb_unlock(struct rcu_data *rdp); 4565d6742b3SPaul E. McKenney static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp, 4575d6742b3SPaul E. McKenney unsigned long flags); 458d1b222c6SPaul E. McKenney static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp); 45935ce7f29SPaul E. McKenney #ifdef CONFIG_RCU_NOCB_CPU 4604580b054SPaul E. McKenney static void __init rcu_organize_nocb_kthreads(void); 461118e0d4aSFrederic Weisbecker 462118e0d4aSFrederic Weisbecker /* 463118e0d4aSFrederic Weisbecker * Disable IRQs before checking offloaded state so that local 464118e0d4aSFrederic Weisbecker * locking is safe against concurrent de-offloading. 465118e0d4aSFrederic Weisbecker */ 46681c0b3d7SPaul E. McKenney #define rcu_nocb_lock_irqsave(rdp, flags) \ 46781c0b3d7SPaul E. McKenney do { \ 46881c0b3d7SPaul E. McKenney local_irq_save(flags); \ 469118e0d4aSFrederic Weisbecker if (rcu_segcblist_is_offloaded(&(rdp)->cblist)) \ 470118e0d4aSFrederic Weisbecker raw_spin_lock(&(rdp)->nocb_lock); \ 47181c0b3d7SPaul E. McKenney } while (0) 47281c0b3d7SPaul E. McKenney #else /* #ifdef CONFIG_RCU_NOCB_CPU */ 47381c0b3d7SPaul E. McKenney #define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags) 47481c0b3d7SPaul E. McKenney #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ 47581c0b3d7SPaul E. McKenney 4764102adabSPaul E. McKenney static void rcu_bind_gp_kthread(void); 4774580b054SPaul E. McKenney static bool rcu_nohz_full_cpu(void); 47832255d51SPaul E. McKenney 47932255d51SPaul E. McKenney /* Forward declarations for tree_stall.h */ 48032255d51SPaul E. McKenney static void record_gp_stall_check_time(void); 4817ac1907cSPaul E. McKenney static void rcu_iw_handler(struct irq_work *iwp); 48232255d51SPaul E. McKenney static void check_cpu_stall(struct rcu_data *rdp); 483b51bcbbfSPaul E. McKenney static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, 484b51bcbbfSPaul E. McKenney const unsigned long gpssdelay); 485d96c52feSPaul E. McKenney 486d96c52feSPaul E. McKenney /* Forward declarations for tree_exp.h. */ 487d96c52feSPaul E. McKenney static void sync_rcu_do_polled_gp(struct work_struct *wp); 488