/* * Read-Copy Update mechanism for mutual exclusion (tree-based version) * * 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: Dipankar Sarma <dipankar@in.ibm.com> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical algorithm * * Based on the original work by Paul McKenney <paulmck@us.ibm.com> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * * For detailed explanation of Read-Copy Update mechanism see - * Documentation/RCU */ #ifndef __LINUX_RCUTREE_H #define __LINUX_RCUTREE_H #include <linux/cache.h> #include <linux/spinlock.h> #include <linux/threads.h> #include <linux/percpu.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 3 #define RCU_FANOUT (CONFIG_RCU_FANOUT) #define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT) #define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * 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 #elif NR_CPUS <= RCU_FANOUT_SQ # define NUM_RCU_LVLS 2 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT) # define NUM_RCU_LVL_2 (NR_CPUS) # define NUM_RCU_LVL_3 0 #elif NR_CPUS <= RCU_FANOUT_CUBE # define NUM_RCU_LVLS 3 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ) # define NUM_RCU_LVL_2 (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT)) # define NUM_RCU_LVL_3 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) #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; unsigned long qsmask; /* CPUs or groups that need to switch in */ /* order for current grace period to proceed.*/ unsigned long qsmaskinit; /* Per-GP initialization for qsmask. */ unsigned long grpmask; /* Mask to apply to parent qsmask. */ 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; } ____cacheline_internodealigned_in_smp; /* 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. */ 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 nxtlist, which is NULL. * * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]): * Entries that might have arrived after current GP ended * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): * Entries known to have arrived before current GP ended * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): * Entries that batch # <= ->completed - 1: waiting for current GP * [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(). */ struct rcu_head *nxtlist; struct rcu_head **nxttail[RCU_NEXT_SIZE]; long qlen; /* # of queued callbacks */ 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) state to allow this CPU to force_quiescent_state on others */ long n_rcu_pending; /* rcu_pending() calls since boot. */ long n_rcu_pending_force_qs; /* when to force quiescent states. */ int cpu; }; /* Values for signaled field in struct rcu_state. */ #define RCU_GP_INIT 0 /* Grace period being initialized. */ #define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */ #define RCU_FORCE_QS 2 /* 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_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. */ spinlock_t onofflock; /* exclude on/offline and */ /* starting new GP. */ 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. */ #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 */ #ifdef CONFIG_NO_HZ long dynticks_completed; /* Value of completed @ snap. */ #endif /* #ifdef CONFIG_NO_HZ */ }; extern struct rcu_state rcu_state; DECLARE_PER_CPU(struct rcu_data, rcu_data); extern struct rcu_state rcu_bh_state; DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); /* * Increment the quiescent state counter. * The counter is a bit degenerated: We do not need to know * how many quiescent states passed, just if there was at least * one since the start of the grace period. Thus just a flag. */ static inline void rcu_qsctr_inc(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_data, cpu); rdp->passed_quiesc = 1; rdp->passed_quiesc_completed = rdp->completed; } static inline void rcu_bh_qsctr_inc(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); rdp->passed_quiesc = 1; rdp->passed_quiesc_completed = rdp->completed; } extern int rcu_pending(int cpu); extern int rcu_needs_cpu(int cpu); #ifdef CONFIG_DEBUG_LOCK_ALLOC extern struct lockdep_map rcu_lock_map; # define rcu_read_acquire() \ lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) # define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) #else # define rcu_read_acquire() do { } while (0) # define rcu_read_release() do { } while (0) #endif static inline void __rcu_read_lock(void) { preempt_disable(); __acquire(RCU); rcu_read_acquire(); } static inline void __rcu_read_unlock(void) { rcu_read_release(); __release(RCU); preempt_enable(); } static inline void __rcu_read_lock_bh(void) { local_bh_disable(); __acquire(RCU_BH); rcu_read_acquire(); } static inline void __rcu_read_unlock_bh(void) { rcu_read_release(); __release(RCU_BH); local_bh_enable(); } #define __synchronize_sched() synchronize_rcu() #define call_rcu_sched(head, func) call_rcu(head, func) static inline void rcu_init_sched(void) { } extern void __rcu_init(void); extern void rcu_check_callbacks(int cpu, int user); extern void rcu_restart_cpu(int cpu); extern long rcu_batches_completed(void); extern long rcu_batches_completed_bh(void); #ifdef CONFIG_NO_HZ void rcu_enter_nohz(void); void rcu_exit_nohz(void); #else /* CONFIG_NO_HZ */ static inline void rcu_enter_nohz(void) { } static inline void rcu_exit_nohz(void) { } #endif /* CONFIG_NO_HZ */ /* A context switch is a grace period for rcutree. */ static inline int rcu_blocking_is_gp(void) { return num_online_cpus() == 1; } #endif /* __LINUX_RCUTREE_H */