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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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768dfffdff
This is a port of commit #b0d3041 from TREE_RCU to TREE_PREEMPT_RCU. Under some rare but real combinations of configuration parameters, RCU callbacks are posted during early boot that use kernel facilities that are not yet initialized. Therefore, when these callbacks are invoked, hard hangs and crashes ensue. This commit therefore prevents RCU callbacks from being invoked until after the scheduler is fully up and running, as in after multiple tasks have been spawned. It might well turn out that a better approach is to identify the specific RCU callbacks that are causing this problem, but that discussion will wait until such time as someone really needs an RCU callback to be invoked (as opposed to merely registered) during early boot. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
172 lines
3.5 KiB
C
172 lines
3.5 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
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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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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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_TINY_H
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#define __LINUX_TINY_H
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#include <linux/cache.h>
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static inline void rcu_init(void)
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{
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}
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static inline void rcu_barrier_bh(void)
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{
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wait_rcu_gp(call_rcu_bh);
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}
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static inline void rcu_barrier_sched(void)
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{
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wait_rcu_gp(call_rcu_sched);
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}
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#ifdef CONFIG_TINY_RCU
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static inline void synchronize_rcu_expedited(void)
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{
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synchronize_sched(); /* Only one CPU, so pretty fast anyway!!! */
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}
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static inline void rcu_barrier(void)
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{
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rcu_barrier_sched(); /* Only one CPU, so only one list of callbacks! */
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}
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#else /* #ifdef CONFIG_TINY_RCU */
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void synchronize_rcu_expedited(void);
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static inline void rcu_barrier(void)
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{
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wait_rcu_gp(call_rcu);
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}
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#endif /* #else #ifdef CONFIG_TINY_RCU */
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static inline void synchronize_rcu_bh(void)
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{
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synchronize_sched();
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}
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static inline void synchronize_rcu_bh_expedited(void)
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{
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synchronize_sched();
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}
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static inline void synchronize_sched_expedited(void)
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{
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synchronize_sched();
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}
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static inline void kfree_call_rcu(struct rcu_head *head,
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void (*func)(struct rcu_head *rcu))
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{
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call_rcu(head, func);
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}
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#ifdef CONFIG_TINY_RCU
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static inline void rcu_preempt_note_context_switch(void)
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{
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}
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static inline void exit_rcu(void)
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{
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}
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static inline int rcu_needs_cpu(int cpu)
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{
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return 0;
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}
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#else /* #ifdef CONFIG_TINY_RCU */
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void rcu_preempt_note_context_switch(void);
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extern void exit_rcu(void);
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int rcu_preempt_needs_cpu(void);
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static inline int rcu_needs_cpu(int cpu)
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{
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return rcu_preempt_needs_cpu();
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}
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#endif /* #else #ifdef CONFIG_TINY_RCU */
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static inline void rcu_note_context_switch(int cpu)
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{
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rcu_sched_qs(cpu);
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rcu_preempt_note_context_switch();
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}
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/*
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* Take advantage of the fact that there is only one CPU, which
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* allows us to ignore virtualization-based context switches.
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*/
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static inline void rcu_virt_note_context_switch(int cpu)
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{
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}
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/*
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* Return the number of grace periods.
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*/
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static inline long rcu_batches_completed(void)
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{
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return 0;
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}
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/*
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* Return the number of bottom-half grace periods.
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*/
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static inline long rcu_batches_completed_bh(void)
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{
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return 0;
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}
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static inline void rcu_force_quiescent_state(void)
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{
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}
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static inline void rcu_bh_force_quiescent_state(void)
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{
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}
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static inline void rcu_sched_force_quiescent_state(void)
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{
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}
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static inline void rcu_cpu_stall_reset(void)
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{
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}
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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extern int rcu_scheduler_active __read_mostly;
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extern void rcu_scheduler_starting(void);
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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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static inline void rcu_scheduler_starting(void)
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{
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}
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#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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#endif /* __LINUX_RCUTINY_H */
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