336 lines
12 KiB
C
336 lines
12 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion (tree-based version)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright IBM Corporation, 2008
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*
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* Author: Dipankar Sarma <dipankar@in.ibm.com>
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* Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical algorithm
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*
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* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
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* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU
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*/
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#ifndef __LINUX_RCUTREE_H
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#define __LINUX_RCUTREE_H
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#include <linux/cache.h>
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#include <linux/spinlock.h>
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#include <linux/threads.h>
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#include <linux/percpu.h>
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#include <linux/cpumask.h>
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#include <linux/seqlock.h>
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/*
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* Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT.
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* In theory, it should be possible to add more levels straightforwardly.
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* In practice, this has not been tested, so there is probably some
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* bug somewhere.
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*/
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#define MAX_RCU_LVLS 3
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#define RCU_FANOUT (CONFIG_RCU_FANOUT)
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#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT)
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#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT)
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#if NR_CPUS <= RCU_FANOUT
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# define NUM_RCU_LVLS 1
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# define NUM_RCU_LVL_0 1
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# define NUM_RCU_LVL_1 (NR_CPUS)
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# define NUM_RCU_LVL_2 0
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# define NUM_RCU_LVL_3 0
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#elif NR_CPUS <= RCU_FANOUT_SQ
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# define NUM_RCU_LVLS 2
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# define NUM_RCU_LVL_0 1
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# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT)
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# define NUM_RCU_LVL_2 (NR_CPUS)
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# define NUM_RCU_LVL_3 0
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#elif NR_CPUS <= RCU_FANOUT_CUBE
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# define NUM_RCU_LVLS 3
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# define NUM_RCU_LVL_0 1
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# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ)
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# define NUM_RCU_LVL_2 (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT))
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# define NUM_RCU_LVL_3 NR_CPUS
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#else
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# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
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#endif /* #if (NR_CPUS) <= RCU_FANOUT */
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#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
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#define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
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/*
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* Dynticks per-CPU state.
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*/
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struct rcu_dynticks {
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int dynticks_nesting; /* Track nesting level, sort of. */
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int dynticks; /* Even value for dynticks-idle, else odd. */
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int dynticks_nmi; /* Even value for either dynticks-idle or */
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/* not in nmi handler, else odd. So this */
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/* remains even for nmi from irq handler. */
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};
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/*
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* Definition for node within the RCU grace-period-detection hierarchy.
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*/
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struct rcu_node {
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spinlock_t lock;
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unsigned long qsmask; /* CPUs or groups that need to switch in */
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/* order for current grace period to proceed.*/
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unsigned long qsmaskinit;
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/* Per-GP initialization for qsmask. */
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unsigned long grpmask; /* Mask to apply to parent qsmask. */
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int grplo; /* lowest-numbered CPU or group here. */
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int grphi; /* highest-numbered CPU or group here. */
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u8 grpnum; /* CPU/group number for next level up. */
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u8 level; /* root is at level 0. */
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struct rcu_node *parent;
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} ____cacheline_internodealigned_in_smp;
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/* Index values for nxttail array in struct rcu_data. */
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#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
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#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
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#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
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#define RCU_NEXT_TAIL 3
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#define RCU_NEXT_SIZE 4
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/* Per-CPU data for read-copy update. */
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struct rcu_data {
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/* 1) quiescent-state and grace-period handling : */
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long completed; /* Track rsp->completed gp number */
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/* in order to detect GP end. */
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long gpnum; /* Highest gp number that this CPU */
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/* is aware of having started. */
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long passed_quiesc_completed;
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/* Value of completed at time of qs. */
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bool passed_quiesc; /* User-mode/idle loop etc. */
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bool qs_pending; /* Core waits for quiesc state. */
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bool beenonline; /* CPU online at least once. */
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struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
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unsigned long grpmask; /* Mask to apply to leaf qsmask. */
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/* 2) batch handling */
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/*
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* If nxtlist is not NULL, it is partitioned as follows.
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* Any of the partitions might be empty, in which case the
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* pointer to that partition will be equal to the pointer for
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* the following partition. When the list is empty, all of
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* the nxttail elements point to nxtlist, which is NULL.
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*
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* [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]):
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* Entries that might have arrived after current GP ended
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* [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
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* Entries known to have arrived before current GP ended
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* [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
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* Entries that batch # <= ->completed - 1: waiting for current GP
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* [nxtlist, *nxttail[RCU_DONE_TAIL]):
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* Entries that batch # <= ->completed
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* The grace period for these entries has completed, and
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* the other grace-period-completed entries may be moved
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* here temporarily in rcu_process_callbacks().
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*/
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struct rcu_head *nxtlist;
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struct rcu_head **nxttail[RCU_NEXT_SIZE];
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long qlen; /* # of queued callbacks */
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long blimit; /* Upper limit on a processed batch */
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#ifdef CONFIG_NO_HZ
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/* 3) dynticks interface. */
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struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */
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int dynticks_snap; /* Per-GP tracking for dynticks. */
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int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */
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#endif /* #ifdef CONFIG_NO_HZ */
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/* 4) reasons this CPU needed to be kicked by force_quiescent_state */
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#ifdef CONFIG_NO_HZ
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unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
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#endif /* #ifdef CONFIG_NO_HZ */
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unsigned long offline_fqs; /* Kicked due to being offline. */
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unsigned long resched_ipi; /* Sent a resched IPI. */
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/* 5) state to allow this CPU to force_quiescent_state on others */
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long n_rcu_pending; /* rcu_pending() calls since boot. */
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long n_rcu_pending_force_qs; /* when to force quiescent states. */
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int cpu;
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};
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/* Values for signaled field in struct rcu_state. */
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#define RCU_GP_INIT 0 /* Grace period being initialized. */
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#define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */
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#define RCU_FORCE_QS 2 /* Need to force quiescent state. */
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#ifdef CONFIG_NO_HZ
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#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
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#else /* #ifdef CONFIG_NO_HZ */
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#define RCU_SIGNAL_INIT RCU_FORCE_QS
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#endif /* #else #ifdef CONFIG_NO_HZ */
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#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
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#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
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#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */
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#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */
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#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */
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/* to take at least one */
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/* scheduling clock irq */
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/* before ratting on them. */
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#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
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/*
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* RCU global state, including node hierarchy. This hierarchy is
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* represented in "heap" form in a dense array. The root (first level)
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* of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
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* level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
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* and the third level in ->node[m+1] and following (->node[m+1] referenced
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* by ->level[2]). The number of levels is determined by the number of
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* CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
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* consisting of a single rcu_node.
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*/
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struct rcu_state {
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struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
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struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */
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u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */
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u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */
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struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */
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/* The following fields are guarded by the root rcu_node's lock. */
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u8 signaled ____cacheline_internodealigned_in_smp;
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/* Force QS state. */
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long gpnum; /* Current gp number. */
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long completed; /* # of last completed gp. */
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spinlock_t onofflock; /* exclude on/offline and */
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/* starting new GP. */
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spinlock_t fqslock; /* Only one task forcing */
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/* quiescent states. */
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unsigned long jiffies_force_qs; /* Time at which to invoke */
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/* force_quiescent_state(). */
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unsigned long n_force_qs; /* Number of calls to */
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/* force_quiescent_state(). */
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unsigned long n_force_qs_lh; /* ~Number of calls leaving */
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/* due to lock unavailable. */
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unsigned long n_force_qs_ngp; /* Number of calls leaving */
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/* due to no GP active. */
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#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
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unsigned long gp_start; /* Time at which GP started, */
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/* but in jiffies. */
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unsigned long jiffies_stall; /* Time at which to check */
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/* for CPU stalls. */
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#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
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#ifdef CONFIG_NO_HZ
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long dynticks_completed; /* Value of completed @ snap. */
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#endif /* #ifdef CONFIG_NO_HZ */
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};
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extern struct rcu_state rcu_state;
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DECLARE_PER_CPU(struct rcu_data, rcu_data);
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extern struct rcu_state rcu_bh_state;
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DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
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/*
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* Increment the quiescent state counter.
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* The counter is a bit degenerated: We do not need to know
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* how many quiescent states passed, just if there was at least
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* one since the start of the grace period. Thus just a flag.
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*/
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static inline void rcu_qsctr_inc(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
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rdp->passed_quiesc = 1;
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rdp->passed_quiesc_completed = rdp->completed;
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}
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static inline void rcu_bh_qsctr_inc(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
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rdp->passed_quiesc = 1;
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rdp->passed_quiesc_completed = rdp->completed;
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}
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extern int rcu_pending(int cpu);
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extern int rcu_needs_cpu(int cpu);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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extern struct lockdep_map rcu_lock_map;
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# define rcu_read_acquire() \
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lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
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# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
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#else
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# define rcu_read_acquire() do { } while (0)
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# define rcu_read_release() do { } while (0)
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#endif
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static inline void __rcu_read_lock(void)
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{
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preempt_disable();
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__acquire(RCU);
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rcu_read_acquire();
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}
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static inline void __rcu_read_unlock(void)
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{
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rcu_read_release();
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__release(RCU);
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preempt_enable();
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}
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static inline void __rcu_read_lock_bh(void)
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{
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local_bh_disable();
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__acquire(RCU_BH);
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rcu_read_acquire();
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}
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static inline void __rcu_read_unlock_bh(void)
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{
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rcu_read_release();
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__release(RCU_BH);
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local_bh_enable();
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}
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#define __synchronize_sched() synchronize_rcu()
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#define call_rcu_sched(head, func) call_rcu(head, func)
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static inline void rcu_init_sched(void)
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{
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}
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extern void __rcu_init(void);
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extern void rcu_check_callbacks(int cpu, int user);
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extern void rcu_restart_cpu(int cpu);
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extern long rcu_batches_completed(void);
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extern long rcu_batches_completed_bh(void);
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#ifdef CONFIG_NO_HZ
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void rcu_enter_nohz(void);
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void rcu_exit_nohz(void);
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#else /* CONFIG_NO_HZ */
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static inline void rcu_enter_nohz(void)
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{
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}
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static inline void rcu_exit_nohz(void)
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{
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}
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#endif /* CONFIG_NO_HZ */
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/* A context switch is a grace period for rcutree. */
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static inline int rcu_blocking_is_gp(void)
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{
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return num_online_cpus() == 1;
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}
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#endif /* __LINUX_RCUTREE_H */
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