/* * 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 { long long dynticks_nesting; /* Track irq/process nesting level. */ /* Process level is worth LLONG_MAX/2. */ int dynticks_nmi_nesting; /* Track NMI nesting level. */ atomic_t dynticks; /* Even value for 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 */ /* 3) dynticks interface. */ struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ int dynticks_snap; /* Per-GP tracking for dynticks. */ /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ 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 fqs_state 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. */ #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK #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 fqs_state ____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_RCU extern struct rcu_state rcu_preempt_state; DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data); #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ #ifdef CONFIG_RCU_BOOST DECLARE_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_CPU static 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_CPU static 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, bool wake); #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); static bool rcu_is_callbacks_kthread(void); #ifdef CONFIG_RCU_BOOST static 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); static void rcu_prepare_for_idle_init(int cpu); static void rcu_cleanup_after_idle(int cpu); static void rcu_prepare_for_idle(int cpu); #endif /* #ifndef RCU_TREE_NONCORE */