/* * Read-Copy Update mechanism for mutual exclusion (tree-based version) * Internal non-public definitions. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * Copyright IBM Corporation, 2008 * * Author: Ingo Molnar <mingo@elte.hu> *	   Paul E. McKenney <paulmck@linux.vnet.ibm.com> */ #include <linux/cache.h>#include <linux/spinlock.h>#include <linux/threads.h>#include <linux/cpumask.h>#include <linux/seqlock.h> /* * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT. * In theory, it should be possible to add more levels straightforwardly. * In practice, this did work well going from three levels to four. * Of course, your mileage may vary. */#define MAX_RCU_LVLS 4#if CONFIG_RCU_FANOUT > 16#define RCU_FANOUT_LEAF       16#else /* #if CONFIG_RCU_FANOUT > 16 */#define RCU_FANOUT_LEAF       (CONFIG_RCU_FANOUT)#endif /* #else #if CONFIG_RCU_FANOUT > 16 */#define RCU_FANOUT_1	      (RCU_FANOUT_LEAF)#define RCU_FANOUT_2	      (RCU_FANOUT_1 * CONFIG_RCU_FANOUT)#define RCU_FANOUT_3	      (RCU_FANOUT_2 * CONFIG_RCU_FANOUT)#define RCU_FANOUT_4	      (RCU_FANOUT_3 * CONFIG_RCU_FANOUT) #if NR_CPUS <= RCU_FANOUT_1#  define NUM_RCU_LVLS	      1#  define NUM_RCU_LVL_0	      1#  define NUM_RCU_LVL_1	      (NR_CPUS)#  define NUM_RCU_LVL_2	      0#  define NUM_RCU_LVL_3	      0#  define NUM_RCU_LVL_4	      0#elif NR_CPUS <= RCU_FANOUT_2#  define NUM_RCU_LVLS	      2#  define NUM_RCU_LVL_0	      1#  define NUM_RCU_LVL_1	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)#  define NUM_RCU_LVL_2	      (NR_CPUS)#  define NUM_RCU_LVL_3	      0#  define NUM_RCU_LVL_4	      0#elif NR_CPUS <= RCU_FANOUT_3#  define NUM_RCU_LVLS	      3#  define NUM_RCU_LVL_0	      1#  define NUM_RCU_LVL_1	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)#  define NUM_RCU_LVL_2	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)#  define NUM_RCU_LVL_3	      (NR_CPUS)#  define NUM_RCU_LVL_4	      0#elif NR_CPUS <= RCU_FANOUT_4#  define NUM_RCU_LVLS	      4#  define NUM_RCU_LVL_0	      1#  define NUM_RCU_LVL_1	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)#  define NUM_RCU_LVL_2	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)#  define NUM_RCU_LVL_3	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)#  define NUM_RCU_LVL_4	      (NR_CPUS)#else# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ #define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4)#define NUM_RCU_NODES (RCU_SUM - NR_CPUS) /* * Dynticks per-CPU state. */struct rcu_dynticks {	int dynticks_nesting;	/* Track irq/process nesting level. */	int dynticks_nmi_nesting; /* Track NMI nesting level. */	atomic_t dynticks;	/* Even value for dynticks-idle, else odd. */}; /* 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 lock;	/* Root rcu_node's lock protects some */				/*  rcu_state fields as well as following. */	unsigned long gpnum;	/* Current grace period for this node. */				/*  This will either be equal to or one */				/*  behind the root rcu_node's gpnum. */	unsigned long completed; /* Last GP completed for this node. */				/*  This will either be equal to or one */				/*  behind the root rcu_node's gpnum. */	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 expmask;	/* Groups that have ->blkd_tasks */				/*  elements that need to drain to allow the */				/*  current expedited grace period to */				/*  complete (only for TREE_PREEMPT_RCU). */	atomic_t wakemask;	/* CPUs whose kthread needs to be awakened. */				/*  Since this has meaning only for leaf */				/*  rcu_node structures, 32 bits suffices. */	unsigned long qsmaskinit;				/* Per-GP initial value for qsmask & expmask. */	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. */	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. */#ifdef CONFIG_RCU_BOOST	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. */	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. */	unsigned long n_tasks_boosted;				/* Total number of tasks boosted. */	unsigned long n_exp_boosts;				/* Number of tasks boosted for expedited GP. */	unsigned long n_normal_boosts;				/* Number of tasks boosted for normal GP. */	unsigned long n_balk_blkd_tasks;				/* Refused to boost: no blocked tasks. */	unsigned long n_balk_exp_gp_tasks;				/* Refused to boost: nothing blocking GP. */	unsigned long n_balk_boost_tasks;				/* Refused to boost: already boosting. */	unsigned long n_balk_notblocked;				/* Refused to boost: RCU RS CS still running. */	unsigned long n_balk_notyet;				/* Refused to boost: not yet time. */	unsigned long n_balk_nos;				/* Refused to boost: not sure why, though. */				/*  This can happen due to race conditions. */#endif /* #ifdef CONFIG_RCU_BOOST */	struct task_struct *node_kthread_task;				/* kthread that takes care of this rcu_node */				/*  structure, for example, awakening the */				/*  per-CPU kthreads as needed. */	unsigned int node_kthread_status;				/* State of node_kthread_task for tracing. */} ____cacheline_internodealigned_in_smp; /* * Do a full breadth-first scan of the rcu_node structures for the * specified rcu_state structure. */#define rcu_for_each_node_breadth_first(rsp, rnp) \	for ((rnp) = &(rsp)->node[0]; \	     (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++) /* * Do a breadth-first scan of the non-leaf rcu_node structures for the * specified rcu_state structure.  Note that if there is a singleton * rcu_node tree with but one rcu_node structure, this loop is a no-op. */#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \	for ((rnp) = &(rsp)->node[0]; \	     (rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++) /* * Scan the leaves of the rcu_node hierarchy for the specified rcu_state * structure.  Note that if there is a singleton rcu_node tree with but * one rcu_node structure, this loop -will- visit the rcu_node structure. * It is still a leaf node, even if it is also the root node. */#define rcu_for_each_leaf_node(rsp, rnp) \	for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \	     (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++) /* Index values for nxttail array in struct rcu_data. */#define RCU_DONE_TAIL		0	/* Also RCU_WAIT head. */#define RCU_WAIT_TAIL		1	/* Also RCU_NEXT_READY head. */#define RCU_NEXT_READY_TAIL	2	/* Also RCU_NEXT head. */#define RCU_NEXT_TAIL		3#define RCU_NEXT_SIZE		4 /* Per-CPU data for read-copy update. */struct rcu_data {	/* 1) quiescent-state and grace-period handling : */	unsigned long	completed;	/* Track rsp->completed gp number */					/*  in order to detect GP end. */	unsigned long	gpnum;		/* Highest gp number that this CPU */					/*  is aware of having started. */	unsigned long	passed_quiesce_gpnum;					/* gpnum at time of quiescent state. */	bool		passed_quiesce;	/* User-mode/idle loop etc. */	bool		qs_pending;	/* Core waits for quiesc state. */	bool		beenonline;	/* CPU online at least once. */	bool		preemptible;	/* Preemptible RCU? */	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */ 	/* 2) batch handling */	/*	 * If nxtlist is not NULL, it is partitioned as follows.	 * Any of the partitions might be empty, in which case the	 * pointer to that partition will be equal to the pointer for	 * the following partition.  When the list is empty, all of	 * the nxttail elements point to the ->nxtlist pointer itself,	 * which in that case is NULL.	 *	 * [nxtlist, *nxttail[RCU_DONE_TAIL]):	 *	Entries that batch # <= ->completed	 *	The grace period for these entries has completed, and	 *	the other grace-period-completed entries may be moved	 *	here temporarily in rcu_process_callbacks().	 * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):	 *	Entries that batch # <= ->completed - 1: waiting for current GP	 * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):	 *	Entries known to have arrived before current GP ended	 * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]):	 *	Entries that might have arrived after current GP ended	 *	Note that the value of *nxttail[RCU_NEXT_TAIL] will	 *	always be NULL, as this is the end of the list.	 */	struct rcu_head *nxtlist;	struct rcu_head **nxttail[RCU_NEXT_SIZE];	long		qlen;		/* # of queued callbacks */	long		qlen_last_fqs_check;					/* qlen at last check for QS forcing */	unsigned long	n_cbs_invoked;	/* count of RCU cbs invoked. */	unsigned long   n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */	unsigned long   n_cbs_adopted;  /* RCU cbs adopted from dying CPU */	unsigned long	n_force_qs_snap;					/* did other CPU force QS recently? */	long		blimit;		/* Upper limit on a processed batch */ #ifdef CONFIG_NO_HZ	/* 3) dynticks interface. */	struct rcu_dynticks *dynticks;	/* Shared per-CPU dynticks state. */	int dynticks_snap;		/* Per-GP tracking for dynticks. */#endif /* #ifdef CONFIG_NO_HZ */ 	/* 4) reasons this CPU needed to be kicked by force_quiescent_state */#ifdef CONFIG_NO_HZ	unsigned long dynticks_fqs;	/* Kicked due to dynticks idle. */#endif /* #ifdef CONFIG_NO_HZ */	unsigned long offline_fqs;	/* Kicked due to being offline. */	unsigned long resched_ipi;	/* Sent a resched IPI. */ 	/* 5) __rcu_pending() statistics. */	unsigned long n_rcu_pending;	/* rcu_pending() calls since boot. */	unsigned long n_rp_qs_pending;	unsigned long n_rp_report_qs;	unsigned long n_rp_cb_ready;	unsigned long n_rp_cpu_needs_gp;	unsigned long n_rp_gp_completed;	unsigned long n_rp_gp_started;	unsigned long n_rp_need_fqs;	unsigned long n_rp_need_nothing; 	int cpu;	struct rcu_state *rsp;}; /* Values for signaled field in struct rcu_state. */#define RCU_GP_IDLE		0	/* No grace period in progress. */#define RCU_GP_INIT		1	/* Grace period being initialized. */#define RCU_SAVE_DYNTICK	2	/* Need to scan dyntick state. */#define RCU_FORCE_QS		3	/* Need to force quiescent state. */#ifdef CONFIG_NO_HZ#define RCU_SIGNAL_INIT		RCU_SAVE_DYNTICK#else /* #ifdef CONFIG_NO_HZ */#define RCU_SIGNAL_INIT		RCU_FORCE_QS#endif /* #else #ifdef CONFIG_NO_HZ */ #define RCU_JIFFIES_TILL_FORCE_QS	 3	/* for rsp->jiffies_force_qs */ #ifdef CONFIG_PROVE_RCU#define RCU_STALL_DELAY_DELTA	       (5 * HZ)#else#define RCU_STALL_DELAY_DELTA	       0#endif #define RCU_SECONDS_TILL_STALL_CHECK   (CONFIG_RCU_CPU_STALL_TIMEOUT * HZ + \					RCU_STALL_DELAY_DELTA)						/* for rsp->jiffies_stall */#define RCU_SECONDS_TILL_STALL_RECHECK (3 * RCU_SECONDS_TILL_STALL_CHECK + 30)						/* for rsp->jiffies_stall */#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[NUM_RCU_LVLS];	/* Hierarchy levels. */	u32 levelcnt[MAX_RCU_LVLS + 1];		/* # nodes in each level. */	u8 levelspread[NUM_RCU_LVLS];		/* kids/node in each level. */	struct rcu_data __percpu *rda;		/* pointer of percu rcu_data. */ 	/* The following fields are guarded by the root rcu_node's lock. */ 	u8	signaled ____cacheline_internodealigned_in_smp;						/* Force QS state. */	u8	fqs_active;			/* force_quiescent_state() */						/*  is running. */	u8	fqs_need_gp;			/* A CPU was prevented from */						/*  starting a new grace */						/*  period because */						/*  force_quiescent_state() */						/*  was running. */	u8	boost;				/* Subject to priority boost. */	unsigned long gpnum;			/* Current gp number. */	unsigned long completed;		/* # of last completed gp. */ 	/* End of fields guarded by root rcu_node's lock. */ 	raw_spinlock_t onofflock;		/* exclude on/offline and */						/*  starting new GP. */	raw_spinlock_t fqslock;			/* Only one task forcing */						/*  quiescent states. */	unsigned long jiffies_force_qs;		/* Time at which to invoke */						/*  force_quiescent_state(). */	unsigned long n_force_qs;		/* Number of calls to */						/*  force_quiescent_state(). */	unsigned long n_force_qs_lh;		/* ~Number of calls leaving */						/*  due to lock unavailable. */	unsigned long n_force_qs_ngp;		/* Number of calls leaving */						/*  due to no GP active. */	unsigned long gp_start;			/* Time at which GP started, */						/*  but in jiffies. */	unsigned long jiffies_stall;		/* Time at which to check */						/*  for CPU stalls. */	unsigned long gp_max;			/* Maximum GP duration in */						/*  jiffies. */	char *name;				/* Name of structure. */}; /* Return values for rcu_preempt_offline_tasks(). */ #define RCU_OFL_TASKS_NORM_GP	0x1		/* Tasks blocking normal */						/*  GP were moved to root. */#define RCU_OFL_TASKS_EXP_GP	0x2		/* Tasks blocking expedited */						/*  GP were moved to root. */ /* * RCU implementation internal declarations: */extern struct rcu_state rcu_sched_state;DECLARE_PER_CPU(struct rcu_data, rcu_sched_data); extern struct rcu_state rcu_bh_state;DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); #ifdef CONFIG_TREE_PREEMPT_RCUextern struct rcu_state rcu_preempt_state;DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ #ifdef CONFIG_RCU_BOOSTDECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);DECLARE_PER_CPU(char, rcu_cpu_has_work);#endif /* #ifdef CONFIG_RCU_BOOST */ #ifndef RCU_TREE_NONCORE /* Forward declarations for rcutree_plugin.h */static void rcu_bootup_announce(void);long rcu_batches_completed(void);static void rcu_preempt_note_context_switch(int cpu);static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);#ifdef CONFIG_HOTPLUG_CPUstatic void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,				      unsigned long flags);static void rcu_stop_cpu_kthread(int cpu);#endif /* #ifdef CONFIG_HOTPLUG_CPU */static void rcu_print_detail_task_stall(struct rcu_state *rsp);static int rcu_print_task_stall(struct rcu_node *rnp);static void rcu_preempt_stall_reset(void);static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);#ifdef CONFIG_HOTPLUG_CPUstatic int rcu_preempt_offline_tasks(struct rcu_state *rsp,				     struct rcu_node *rnp,				     struct rcu_data *rdp);static void rcu_preempt_offline_cpu(int cpu);#endif /* #ifdef CONFIG_HOTPLUG_CPU */static void rcu_preempt_check_callbacks(int cpu);static void rcu_preempt_process_callbacks(void);void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp);#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */static int rcu_preempt_pending(int cpu);static int rcu_preempt_needs_cpu(int cpu);static void __cpuinit rcu_preempt_init_percpu_data(int cpu);static void rcu_preempt_send_cbs_to_online(void);static void __init __rcu_init_preempt(void);static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);static void invoke_rcu_callbacks_kthread(void);#ifdef CONFIG_RCU_BOOSTstatic void rcu_preempt_do_callbacks(void);static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp,					  cpumask_var_t cm);static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,						 struct rcu_node *rnp,						 int rnp_index);static void invoke_rcu_node_kthread(struct rcu_node *rnp);static void rcu_yield(void (*f)(unsigned long), unsigned long arg);#endif /* #ifdef CONFIG_RCU_BOOST */static void rcu_cpu_kthread_setrt(int cpu, int to_rt);static void __cpuinit rcu_prepare_kthreads(int cpu); #endif /* #ifndef RCU_TREE_NONCORE */