/* 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/kthread.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 kthread worker handler. */struct rcu_exp_work {	unsigned long rew_s;	struct kthread_work rew_work;}; /* RCU's kthread states for tracing. */#define RCU_KTHREAD_STOPPED  0#define RCU_KTHREAD_RUNNING  1#define RCU_KTHREAD_WAITING  2#define RCU_KTHREAD_OFFCPU   3#define RCU_KTHREAD_YIELDING 4#define RCU_KTHREAD_MAX      4 /* * Definition for node within the RCU grace-period-detection hierarchy. */struct rcu_node {	raw_spinlock_t __private lock;	/* Root rcu_node's lock protects */					/*  some rcu_state fields as well as */					/*  following. */	unsigned long gp_seq;	/* Track rsp->gp_seq. */	unsigned long gp_seq_needed; /* Track furthest future GP request. */	unsigned long completedqs; /* All QSes done for this node. */	unsigned long qsmask;	/* CPUs or groups that need to switch in */				/*  order for current grace period to proceed.*/				/*  In leaf rcu_node, each bit corresponds to */				/*  an rcu_data structure, otherwise, each */				/*  bit corresponds to a child rcu_node */				/*  structure. */	unsigned long rcu_gp_init_mask;	/* Mask of offline CPUs at GP init. */	unsigned long qsmaskinit;				/* Per-GP initial value for qsmask. */				/*  Initialized from ->qsmaskinitnext at the */				/*  beginning of each grace period. */	unsigned long qsmaskinitnext;	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. */	struct kthread_worker *exp_kworker;				/* Workers performing per node expedited GP */				/* initialization. */	unsigned long cbovldmask;				/* CPUs experiencing callback overload. */	unsigned long ffmask;	/* Fully functional CPUs. */	unsigned long grpmask;	/* Mask to apply to parent qsmask. */				/*  Only one bit will be set in this mask. */	int	grplo;		/* lowest-numbered CPU here. */	int	grphi;		/* highest-numbered CPU here. */	u8	grpnum;		/* group number for next level up. */	u8	level;		/* root is at level 0. */	bool	wait_blkd_tasks;/* Necessary to wait for blocked tasks to */				/*  exit RCU read-side critical sections */				/*  before propagating offline up the */				/*  rcu_node tree? */	struct rcu_node *parent;	struct list_head blkd_tasks;				/* Tasks blocked in RCU read-side critical */				/*  section.  Tasks are placed at the head */				/*  of this list and age towards the tail. */	struct list_head *gp_tasks;				/* Pointer to the first task blocking the */				/*  current grace period, or NULL if there */				/*  is no such task. */	struct list_head *exp_tasks;				/* Pointer to the first task blocking the */				/*  current expedited grace period, or NULL */				/*  if there is no such task.  If there */				/*  is no current expedited grace period, */				/*  then there can cannot be any such task. */	struct list_head *boost_tasks;				/* Pointer to first task that needs to be */				/*  priority boosted, or NULL if no priority */				/*  boosting is needed for this rcu_node */				/*  structure.  If there are no tasks */				/*  queued on this rcu_node structure that */				/*  are blocking the current grace period, */				/*  there can be no such task. */	struct rt_mutex boost_mtx;				/* Used only for the priority-boosting */				/*  side effect, not as a lock. */	unsigned long boost_time;				/* When to start boosting (jiffies). */	struct mutex kthread_mutex;				/* Exclusion for thread spawning and affinity */				/*  manipulation. */	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. */	unsigned long n_boosts;	/* Number of boosts for this rcu_node structure. */#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? */	raw_spinlock_t exp_poll_lock;				/* Lock and data for polled expedited grace periods. */	unsigned long exp_seq_poll_rq;	struct work_struct exp_poll_wq;} ____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. */}; /* * Record the snapshot of the core stats at half of the first RCU stall timeout. * The member gp_seq is used to ensure that all members are updated only once * during the sampling period. The snapshot is taken only if this gp_seq is not * equal to rdp->gp_seq. */struct rcu_snap_record {	unsigned long	gp_seq;		/* Track rdp->gp_seq counter */	u64		cputime_irq;	/* Accumulated cputime of hard irqs */	u64		cputime_softirq;/* Accumulated cputime of soft irqs */	u64		cputime_system; /* Accumulated cputime of kernel tasks */	u64		nr_hardirqs;	/* Accumulated number of hard irqs */	unsigned int	nr_softirqs;	/* Accumulated number of soft irqs */	unsigned long long nr_csw;	/* Accumulated number of task switches */	unsigned long   jiffies;	/* Track jiffies value */}; /* * An IRQ work (deferred_qs_iw) is used by RCU to get the scheduler's attention. * to report quiescent states at the soonest possible time. * The request can be in one of the following states: * - DEFER_QS_IDLE: An IRQ work is yet to be scheduled. * - DEFER_QS_PENDING: An IRQ work was scheduled but either not yet run, or it *                     ran and we still haven't reported a quiescent state. */#define DEFER_QS_IDLE		0#define DEFER_QS_PENDING	1 /* Per-CPU data for read-copy update. */struct rcu_data {	/* 1) quiescent-state and grace-period handling : */	unsigned long	gp_seq;		/* Track rsp->gp_seq counter. */	unsigned long	gp_seq_needed;	/* Track furthest future GP request. */	union rcu_noqs	cpu_no_qs;	/* No QSes yet for this CPU. */	bool		core_needs_qs;	/* Core waits for quiescent state. */	bool		beenonline;	/* CPU online at least once. */	bool		gpwrap;		/* Possible ->gp_seq wrap. */	unsigned int	gpwrap_count;	/* Count of GP sequence wrap. */	bool		cpu_started;	/* RCU watching this onlining CPU. */	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */	unsigned long	ticks_this_gp;	/* The number of scheduling-clock */					/*  ticks this CPU has handled */					/*  during and after the last grace */					/* period it is aware of. */	struct irq_work defer_qs_iw;	/* Obtain later scheduler attention. */	int defer_qs_pending;		/* irqwork or softirq pending? */	struct work_struct strict_work;	/* Schedule readers for strict GPs. */ 	/* 2) batch handling */	struct rcu_segcblist cblist;	/* Segmented callback list, with */					/* different callbacks waiting for */					/* different grace periods. */	long		qlen_last_fqs_check;					/* qlen at last check for QS forcing */	unsigned long	n_cbs_invoked;	/* # callbacks invoked since boot. */	unsigned long	n_force_qs_snap;					/* did other CPU force QS recently? */	long		blimit;		/* Upper limit on a processed batch */ 	/* 3) dynticks interface. */	int  watching_snap;		/* Per-GP tracking for dynticks. */	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. */ 	/* 4) rcu_barrier(), OOM callbacks, and expediting. */	unsigned long barrier_seq_snap;	/* Snap of rcu_state.barrier_sequence. */	struct rcu_head barrier_head;	int exp_watching_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 swait_queue_head nocb_state_wq; /* For offloading state changes */	struct task_struct *nocb_gp_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. */	unsigned long nocb_gp_adv_time;	/* Last call_rcu() CB adv (jiffies). */	struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */					    /* spawning */ 	/* 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;	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? */	struct rcu_gp_seq nocb_gp_seq; /* If so, GP state 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 list_head nocb_head_rdp; /*					 * Head of rcu_data list in wakeup chain,					 * if rdp_gp.					 */	struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */	struct rcu_data *nocb_toggling_rdp; /* rdp queued for (de-)offloading */ 	/* 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;	unsigned long rcuc_activity; 	/* 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_state;		/* ->gp_state at last offline. */	unsigned long rcu_onl_gp_seq;	/* ->gp_seq at last online. */	short rcu_onl_gp_state;		/* ->gp_state at last online. */	unsigned long last_fqs_resched;	/* Time of last rcu_resched(). */	unsigned long last_sched_clock;	/* Jiffies of last rcu_sched_clock_irq(). */	struct rcu_snap_record snap_record; /* Snapshot of core stats at half of */					    /* the first RCU stall timeout */ 	long lazy_len;			/* Length of buffered lazy callbacks. */	int cpu;}; static inline void rcu_defer_qs_clear(struct rcu_data *rdp){	WRITE_ONCE(rdp->defer_qs_pending, DEFER_QS_IDLE);} /* Values for nocb_defer_wakeup field in struct rcu_data. */#define RCU_NOCB_WAKE_NOT	0#define RCU_NOCB_WAKE_BYPASS	1#define RCU_NOCB_WAKE_LAZY	2#define RCU_NOCB_WAKE		3 #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) /* * A max threshold for synchronize_rcu() users which are * awaken directly by the rcu_gp_kthread(). Left part is * deferred to the main worker. */#define SR_MAX_USERS_WAKE_FROM_GP 5#define SR_NORMAL_GP_WAIT_HEAD_MAX 5 struct sr_wait_node {	atomic_t inuse;	struct llist_node node;}; /* * 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. */	int n_online_cpus;			/* # CPUs online for RCU. */ 	/* The following fields are guarded by the root rcu_node's lock. */ 	unsigned long gp_seq ____cacheline_internodealigned_in_smp;						/* Grace-period sequence #. */	unsigned long gp_max;			/* Maximum GP duration in */						/*  jiffies. */	struct task_struct *gp_kthread;		/* Task for grace periods. */	struct swait_queue_head gp_wq;		/* Where GP task waits. */	short gp_flags;				/* Commands for GP task. */	short gp_state;				/* GP kthread sleep state. */	unsigned long gp_wake_time;		/* Last GP kthread wake. */	unsigned long gp_wake_seq;		/* ->gp_seq at ^^^. */	unsigned long gp_seq_polled;		/* GP seq for polled API. */	unsigned long gp_seq_polled_snap;	/* ->gp_seq_polled at normal GP start. */	unsigned long gp_seq_polled_exp_snap;	/* ->gp_seq_polled at expedited GP start. */ 	/* 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. */ 	raw_spinlock_t barrier_lock;		/* Protects ->barrier_seq_snap. */ 	struct mutex exp_mutex;			/* Serialize expedited GP. */	struct mutex exp_wake_mutex;		/* Serialize wakeup. */	unsigned long expedited_sequence;	/* Take a ticket. */	struct swait_queue_head expedited_wq;	/* Wait for check-ins. */	int ncpus_snap;				/* # CPUs seen last time. */	u8 cbovld;				/* Callback overload now? */	u8 cbovldnext;				/* ^        ^  next time? */ 	unsigned long jiffies_force_qs;		/* Time at which to invoke */						/*  force_quiescent_state(). */	unsigned long jiffies_kick_kthreads;	/* Time at which to kick */						/*  kthreads, if configured. */	unsigned long n_force_qs;		/* Number of calls to */						/*  force_quiescent_state(). */	unsigned long gp_start;			/* Time at which GP started, */						/*  but in jiffies. */	unsigned long gp_end;			/* Time last GP ended, again */						/*  in jiffies. */	unsigned long gp_activity;		/* Time of last GP kthread */						/*  activity in jiffies. */	unsigned long gp_req_activity;		/* Time of last GP request */						/*  in jiffies. */	unsigned long jiffies_stall;		/* Time at which to check */						/*  for CPU stalls. */	int nr_fqs_jiffies_stall;		/* Number of fqs loops after						 * which read jiffies and set						 * jiffies_stall. Stall						 * warnings disabled if !0. */	unsigned long jiffies_resched;		/* Time at which to resched */						/*  a reluctant CPU. */	unsigned long n_force_qs_gpstart;	/* Snapshot of n_force_qs at */						/*  GP start. */	const char *name;			/* Name of structure. */	char abbr;				/* Abbreviated name. */ 	arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;						/* Synchronize offline with */						/*  GP pre-initialization. */ 	/* synchronize_rcu() part. */	struct llist_head srs_next;	/* request a GP users. */	struct llist_node *srs_wait_tail; /* wait for GP users. */	struct llist_node *srs_done_tail; /* ready for GP users. */	struct sr_wait_node srs_wait_nodes[SR_NORMAL_GP_WAIT_HEAD_MAX];	struct work_struct srs_cleanup_work;	atomic_t srs_cleanups_pending; /* srs inflight worker cleanups. */ #ifdef CONFIG_RCU_NOCB_CPU	struct mutex nocb_mutex;		/* Guards (de-)offloading */	int nocb_is_setup;			/* nocb is setup from boot */#endif}; /* Values for rcu_state structure's gp_flags field. */#define RCU_GP_FLAG_INIT 0x1	/* Need grace-period initialization. */#define RCU_GP_FLAG_FQS  0x2	/* Need grace-period quiescent-state forcing. */#define RCU_GP_FLAG_OVLD 0x4	/* Experiencing callback overload. */ /* Values for rcu_state structure's gp_state field. */#define RCU_GP_IDLE	 0	/* Initial state and no GP in progress. */#define RCU_GP_WAIT_GPS  1	/* Wait for grace-period start. */#define RCU_GP_DONE_GPS  2	/* Wait done for grace-period start. */#define RCU_GP_ONOFF     3	/* Grace-period initialization hotplug. */#define RCU_GP_INIT      4	/* Grace-period initialization. */#define RCU_GP_WAIT_FQS  5	/* Wait for force-quiescent-state time. */#define RCU_GP_DOING_FQS 6	/* Wait done for force-quiescent-state time. */#define RCU_GP_CLEANUP   7	/* Grace-period cleanup started. */#define RCU_GP_CLEANED   8	/* Grace-period cleanup complete. */ /* * In order to export the rcu_state name to the tracing tools, it * needs to be added in the __tracepoint_string section. * This requires defining a separate variable tp_<sname>_varname * that points to the string being used, and this will allow * the tracing userspace tools to be able to decipher the string * address to the matching string. */#ifdef CONFIG_PREEMPT_RCU#define RCU_ABBR 'p'#define RCU_NAME_RAW "rcu_preempt"#else /* #ifdef CONFIG_PREEMPT_RCU */#define RCU_ABBR 's'#define RCU_NAME_RAW "rcu_sched"#endif /* #else #ifdef CONFIG_PREEMPT_RCU */#ifndef CONFIG_TRACING#define RCU_NAME RCU_NAME_RAW#else /* #ifdef CONFIG_TRACING */static char rcu_name[] = RCU_NAME_RAW;static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;#define RCU_NAME rcu_name#endif /* #else #ifdef CONFIG_TRACING */ /* Forward declarations for tree_plugin.h */static void rcu_bootup_announce(void);static void rcu_qs(void);static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);#ifdef CONFIG_HOTPLUG_CPUstatic 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_preempt_deferred_qs_init(struct rcu_data *rdp);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(struct rcu_data *rdp);static void rcu_cpu_kthread_setup(unsigned int cpu);static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);static bool rcu_preempt_has_tasks(struct rcu_node *rnp);

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