| /* 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->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. */ |
| 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 #. */ |
| 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. */ |
| |
| /* |
| * 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); |
| |
| /* 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); |
