| /* |
| * 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_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 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; |
| }; |
| |
| /* 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. */ |
| 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 */ |
| |
| #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); |
| #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
| static void rcu_print_detail_task_stall(struct rcu_state *rsp); |
| static void 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); |
| #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_needs_cpu_flush(void); |
| static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags); |
| static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, |
| cpumask_var_t cm); |
| static void rcu_preempt_boost_start_gp(struct rcu_node *rnp); |
| static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, |
| struct rcu_node *rnp, |
| int rnp_index); |
| |
| #endif /* #ifndef RCU_TREE_NONCORE */ |
