2232c2d8e0
The PREEMPT-RCU can get stuck if a CPU goes idle and NO_HZ is set. The idle CPU will not progress the RCU through its grace period and a synchronize_rcu my get stuck. Without this patch I have a box that will not boot when PREEMPT_RCU and NO_HZ are set. That same box boots fine with this patch. This patch comes from the -rt kernel where it has been tested for several months. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
168 lines
4.8 KiB
C
168 lines
4.8 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion (classic 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, 2001
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*
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* Author: Dipankar Sarma <dipankar@in.ibm.com>
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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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* Papers:
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* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
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* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
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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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*/
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#ifndef __LINUX_RCUCLASSIC_H
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#define __LINUX_RCUCLASSIC_H
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#ifdef __KERNEL__
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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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/* Global control variables for rcupdate callback mechanism. */
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struct rcu_ctrlblk {
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long cur; /* Current batch number. */
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long completed; /* Number of the last completed batch */
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int next_pending; /* Is the next batch already waiting? */
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int signaled;
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spinlock_t lock ____cacheline_internodealigned_in_smp;
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cpumask_t cpumask; /* CPUs that need to switch in order */
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/* for current batch to proceed. */
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} ____cacheline_internodealigned_in_smp;
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/* Is batch a before batch b ? */
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static inline int rcu_batch_before(long a, long b)
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{
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return (a - b) < 0;
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}
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/* Is batch a after batch b ? */
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static inline int rcu_batch_after(long a, long b)
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{
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return (a - b) > 0;
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}
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/*
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* Per-CPU data for Read-Copy UPdate.
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* nxtlist - new callbacks are added here
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* curlist - current batch for which quiescent cycle started if any
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*/
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struct rcu_data {
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/* 1) quiescent state handling : */
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long quiescbatch; /* Batch # for grace period */
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int passed_quiesc; /* User-mode/idle loop etc. */
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int qs_pending; /* core waits for quiesc state */
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/* 2) batch handling */
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long batch; /* Batch # for current RCU batch */
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struct rcu_head *nxtlist;
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struct rcu_head **nxttail;
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long qlen; /* # of queued callbacks */
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struct rcu_head *curlist;
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struct rcu_head **curtail;
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struct rcu_head *donelist;
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struct rcu_head **donetail;
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long blimit; /* Upper limit on a processed batch */
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int cpu;
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struct rcu_head barrier;
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};
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DECLARE_PER_CPU(struct rcu_data, rcu_data);
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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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}
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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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}
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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, _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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#define __rcu_read_lock() \
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do { \
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preempt_disable(); \
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__acquire(RCU); \
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rcu_read_acquire(); \
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} while (0)
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#define __rcu_read_unlock() \
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do { \
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rcu_read_release(); \
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__release(RCU); \
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preempt_enable(); \
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} while (0)
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#define __rcu_read_lock_bh() \
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do { \
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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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} while (0)
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#define __rcu_read_unlock_bh() \
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do { \
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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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} while (0)
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#define __synchronize_sched() synchronize_rcu()
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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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#define rcu_enter_nohz() do { } while (0)
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#define rcu_exit_nohz() do { } while (0)
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#endif /* __KERNEL__ */
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#endif /* __LINUX_RCUCLASSIC_H */
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