/* * 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 has not been tested, so there is probably some * bug somewhere. */ #define MAX_RCU_LVLS 4 #define RCU_FANOUT (CONFIG_RCU_FANOUT) #define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT) #define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT) #define RCU_FANOUT_FOURTH (RCU_FANOUT_CUBE * RCU_FANOUT) #if NR_CPUS <= RCU_FANOUT # 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_SQ # define NUM_RCU_LVLS 2 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT) # define NUM_RCU_LVL_2 (NR_CPUS) # define NUM_RCU_LVL_3 0 # define NUM_RCU_LVL_4 0 #elif NR_CPUS <= RCU_FANOUT_CUBE # define NUM_RCU_LVLS 3 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ) # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT) # define NUM_RCU_LVL_3 NR_CPUS # define NUM_RCU_LVL_4 0 #elif NR_CPUS <= RCU_FANOUT_FOURTH # define NUM_RCU_LVLS 4 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_CUBE) # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ) # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT) # define NUM_RCU_LVL_4 NR_CPUS #else # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" #endif /* #if (NR_CPUS) <= RCU_FANOUT */ #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 nesting level, sort of. */ int dynticks; /* Even value for dynticks-idle, else odd. */ int dynticks_nmi; /* Even value for either dynticks-idle or */ /* not in nmi handler, else odd. So this */ /* remains even for nmi from irq handler. */ }; /* * Definition for node within the RCU grace-period-detection hierarchy. */ struct rcu_node { spinlock_t lock; /* Root rcu_node's lock protects some */ /* rcu_state fields as well as following. */ long gpnum; /* Current grace period for this node. */ /* This will either be equal to or one */ /* behind the root rcu_node's gpnum. */ long completed; /* Last grace period 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 ->blocked_tasks[] */ /* elements that need to drain to allow the */ /* current expedited grace period to */ /* complete (only for TREE_PREEMPT_RCU). */ 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 blocked_tasks[4]; /* Tasks blocked in RCU read-side critsect. */ /* Grace period number (->gpnum) x blocked */ /* by tasks on the (x & 0x1) element of the */ /* blocked_tasks[] array. */ } ____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 : */ long completed; /* Track rsp->completed gp number */ /* in order to detect GP end. */ long gpnum; /* Highest gp number that this CPU */ /* is aware of having started. */ long passed_quiesc_completed; /* Value of completed at time of qs. */ bool passed_quiesc; /* User-mode/idle loop etc. */ bool qs_pending; /* Core waits for quiesc state. */ bool beenonline; /* CPU online at least once. */ bool preemptable; /* Preemptable 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_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. */ int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */ #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. */ long n_rcu_pending; /* rcu_pending() calls since boot. */ long n_rp_qs_pending; long n_rp_cb_ready; long n_rp_cpu_needs_gp; long n_rp_gp_completed; long n_rp_gp_started; long n_rp_need_fqs; long n_rp_need_nothing; int cpu; }; /* 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_SAVE_COMPLETED 3 /* Need to save rsp->completed. */ #define RCU_FORCE_QS 4 /* 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_SAVE_COMPLETED #endif /* #else #ifdef CONFIG_NO_HZ */ #define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ #ifdef CONFIG_RCU_CPU_STALL_DETECTOR #define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */ #define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* 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. */ #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ /* * 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 *rda[NR_CPUS]; /* array of rdp pointers. */ /* The following fields are guarded by the root rcu_node's lock. */ u8 signaled ____cacheline_internodealigned_in_smp; /* Force QS state. */ long gpnum; /* Current gp number. */ long completed; /* # of last completed gp. */ /* End of fields guarded by root rcu_node's lock. */ spinlock_t onofflock; /* exclude on/offline and */ /* starting new GP. Also */ /* protects the following */ /* orphan_cbs fields. */ struct rcu_head *orphan_cbs_list; /* list of rcu_head structs */ /* orphaned by all CPUs in */ /* a given leaf rcu_node */ /* going offline. */ struct rcu_head **orphan_cbs_tail; /* And tail pointer. */ long orphan_qlen; /* Number of orphaned cbs. */ spinlock_t fqslock; /* Only one task forcing */ /* quiescent states. */ long completed_fqs; /* Value of completed @ snap. */ /* Protected by fqslock. */ 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. */ #ifdef CONFIG_RCU_CPU_STALL_DETECTOR unsigned long gp_start; /* Time at which GP started, */ /* but in jiffies. */ unsigned long jiffies_stall; /* Time at which to check */ /* for CPU stalls. */ #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ }; /* 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. */ #ifdef RCU_TREE_NONCORE /* * 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 */ #else /* #ifdef 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_preempted_readers(struct rcu_node *rnp); #ifdef CONFIG_HOTPLUG_CPU static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags); #endif /* #ifdef CONFIG_HOTPLUG_CPU */ #ifdef CONFIG_RCU_CPU_STALL_DETECTOR static void rcu_print_task_stall(struct rcu_node *rnp); #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ 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); #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_orphanage(void); static void __init __rcu_init_preempt(void); #endif /* #else #ifdef RCU_TREE_NONCORE */