3705b88db0
There have been some embedded applications that would benefit from use of expedited grace-period primitives. In some ways, this is similar to synchronize_net() doing either a normal or an expedited grace period depending on lock state, but with control outside of the kernel. This commit therefore adds rcu_expedited boot and sysfs parameters that cause the kernel to substitute expedited primitives for the normal grace-period primitives. [ paulmck: Add trace/event/rcu.h to kernel/srcu.c to avoid build error. Get rid of infinite loop through contention path.] Signed-off-by: Antti P Miettinen <amiettinen@nvidia.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
114 lines
3.8 KiB
C
114 lines
3.8 KiB
C
/*
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* Read-Copy Update definitions shared among RCU implementations.
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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, 2011
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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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#ifndef __LINUX_RCU_H
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#define __LINUX_RCU_H
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#ifdef CONFIG_RCU_TRACE
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#define RCU_TRACE(stmt) stmt
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#else /* #ifdef CONFIG_RCU_TRACE */
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#define RCU_TRACE(stmt)
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#endif /* #else #ifdef CONFIG_RCU_TRACE */
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/*
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* Process-level increment to ->dynticks_nesting field. This allows for
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* architectures that use half-interrupts and half-exceptions from
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* process context.
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*
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* DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH
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* that counts the number of process-based reasons why RCU cannot
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* consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE
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* is the value used to increment or decrement this field.
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*
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* The rest of the bits could in principle be used to count interrupts,
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* but this would mean that a negative-one value in the interrupt
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* field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field.
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* We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK
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* that is set to DYNTICK_TASK_FLAG upon initial exit from idle.
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* The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon
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* initial exit from idle.
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*/
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#define DYNTICK_TASK_NEST_WIDTH 7
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#define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1)
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#define DYNTICK_TASK_NEST_MASK (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1)
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#define DYNTICK_TASK_FLAG ((DYNTICK_TASK_NEST_VALUE / 8) * 2)
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#define DYNTICK_TASK_MASK ((DYNTICK_TASK_NEST_VALUE / 8) * 3)
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#define DYNTICK_TASK_EXIT_IDLE (DYNTICK_TASK_NEST_VALUE + \
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DYNTICK_TASK_FLAG)
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/*
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* debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
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* by call_rcu() and rcu callback execution, and are therefore not part of the
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* RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
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*/
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#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
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# define STATE_RCU_HEAD_READY 0
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# define STATE_RCU_HEAD_QUEUED 1
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extern struct debug_obj_descr rcuhead_debug_descr;
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static inline void debug_rcu_head_queue(struct rcu_head *head)
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{
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debug_object_activate(head, &rcuhead_debug_descr);
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debug_object_active_state(head, &rcuhead_debug_descr,
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STATE_RCU_HEAD_READY,
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STATE_RCU_HEAD_QUEUED);
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}
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static inline void debug_rcu_head_unqueue(struct rcu_head *head)
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{
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debug_object_active_state(head, &rcuhead_debug_descr,
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STATE_RCU_HEAD_QUEUED,
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STATE_RCU_HEAD_READY);
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debug_object_deactivate(head, &rcuhead_debug_descr);
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}
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#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
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static inline void debug_rcu_head_queue(struct rcu_head *head)
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{
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}
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static inline void debug_rcu_head_unqueue(struct rcu_head *head)
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{
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}
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#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
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extern void kfree(const void *);
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static inline bool __rcu_reclaim(char *rn, struct rcu_head *head)
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{
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unsigned long offset = (unsigned long)head->func;
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if (__is_kfree_rcu_offset(offset)) {
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RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
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kfree((void *)head - offset);
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return 1;
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} else {
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RCU_TRACE(trace_rcu_invoke_callback(rn, head));
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head->func(head);
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return 0;
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}
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}
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extern int rcu_expedited;
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#endif /* __LINUX_RCU_H */
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