| /* 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/stop_machine.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->rcu_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 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 or group here. */ | |
| int grphi; /* highest-numbered CPU or group here. */ | |
| u8 grpnum; /* CPU/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->rcu_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? */ | |
| 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? */ | |
| /* 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_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. */ | |
| #ifdef CONFIG_RCU_FAST_NO_HZ | |
| bool all_lazy; /* All CPU's CBs lazy at idle start? */ | |
| 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 rcu_head *nocb_head; /* CBs waiting for kthread. */ | |
| struct rcu_head **nocb_tail; | |
| atomic_long_t nocb_q_count; /* # CBs waiting for nocb */ | |
| atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */ | |
| struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */ | |
| struct rcu_head **nocb_follower_tail; | |
| struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */ | |
| struct task_struct *nocb_kthread; | |
| raw_spinlock_t nocb_lock; /* Guard following pair of fields. */ | |
| int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ | |
| struct timer_list nocb_timer; /* Enforce finite deferral. */ | |
| /* The following fields are used by the leader, hence own cacheline. */ | |
| struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp; | |
| /* CBs waiting for GP. */ | |
| struct rcu_head **nocb_gp_tail; | |
| bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */ | |
| struct rcu_data *nocb_next_follower; | |
| /* Next follower in wakeup chain. */ | |
| /* The following fields are used by the follower, hence new cachline. */ | |
| struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp; | |
| /* Leader CPU 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 #. */ | |
| 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. */ | |
| 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. */ | |
| unsigned long gp_max; /* Maximum GP duration in */ | |
| /* jiffies. */ | |
| 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. */ | |
| /* 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. */ | |
| static const char * const gp_state_names[] = { | |
| "RCU_GP_IDLE", | |
| "RCU_GP_WAIT_GPS", | |
| "RCU_GP_DONE_GPS", | |
| "RCU_GP_ONOFF", | |
| "RCU_GP_INIT", | |
| "RCU_GP_WAIT_FQS", | |
| "RCU_GP_DOING_FQS", | |
| "RCU_GP_CLEANUP", | |
| "RCU_GP_CLEANED", | |
| }; | |
| /* | |
| * 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 */ | |
| int rcu_dynticks_snap(struct rcu_data *rdp); | |
| /* 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); | |
| void call_rcu(struct rcu_head *head, rcu_callback_t func); | |
| 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 bool rcu_nocb_cpu_needs_barrier(int cpu); | |
| 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 __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, | |
| bool lazy, unsigned long flags); | |
| static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp, | |
| struct rcu_data *rdp, | |
| 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); | |
| #ifdef CONFIG_RCU_NOCB_CPU | |
| static void __init rcu_organize_nocb_kthreads(void); | |
| #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ | |
| static bool init_nocb_callback_list(struct rcu_data *rdp); | |
| static unsigned long rcu_get_n_cbs_nocb_cpu(struct rcu_data *rdp); | |
| 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); | |
| /* 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); |