1 /* 2 * Read-Copy Update definitions shared among RCU implementations. 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, you can access it online at 16 * http://www.gnu.org/licenses/gpl-2.0.html. 17 * 18 * Copyright IBM Corporation, 2011 19 * 20 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> 21 */ 22 23 #ifndef __LINUX_RCU_H 24 #define __LINUX_RCU_H 25 26 #include <trace/events/rcu.h> 27 #ifdef CONFIG_RCU_TRACE 28 #define RCU_TRACE(stmt) stmt 29 #else /* #ifdef CONFIG_RCU_TRACE */ 30 #define RCU_TRACE(stmt) 31 #endif /* #else #ifdef CONFIG_RCU_TRACE */ 32 33 /* 34 * Process-level increment to ->dynticks_nesting field. This allows for 35 * architectures that use half-interrupts and half-exceptions from 36 * process context. 37 * 38 * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH 39 * that counts the number of process-based reasons why RCU cannot 40 * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE 41 * is the value used to increment or decrement this field. 42 * 43 * The rest of the bits could in principle be used to count interrupts, 44 * but this would mean that a negative-one value in the interrupt 45 * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field. 46 * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK 47 * that is set to DYNTICK_TASK_FLAG upon initial exit from idle. 48 * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon 49 * initial exit from idle. 50 */ 51 #define DYNTICK_TASK_NEST_WIDTH 7 52 #define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1) 53 #define DYNTICK_TASK_NEST_MASK (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1) 54 #define DYNTICK_TASK_FLAG ((DYNTICK_TASK_NEST_VALUE / 8) * 2) 55 #define DYNTICK_TASK_MASK ((DYNTICK_TASK_NEST_VALUE / 8) * 3) 56 #define DYNTICK_TASK_EXIT_IDLE (DYNTICK_TASK_NEST_VALUE + \ 57 DYNTICK_TASK_FLAG) 58 59 /* 60 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally 61 * by call_rcu() and rcu callback execution, and are therefore not part of the 62 * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. 63 */ 64 65 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD 66 # define STATE_RCU_HEAD_READY 0 67 # define STATE_RCU_HEAD_QUEUED 1 68 69 extern struct debug_obj_descr rcuhead_debug_descr; 70 71 static inline int debug_rcu_head_queue(struct rcu_head *head) 72 { 73 int r1; 74 75 r1 = debug_object_activate(head, &rcuhead_debug_descr); 76 debug_object_active_state(head, &rcuhead_debug_descr, 77 STATE_RCU_HEAD_READY, 78 STATE_RCU_HEAD_QUEUED); 79 return r1; 80 } 81 82 static inline void debug_rcu_head_unqueue(struct rcu_head *head) 83 { 84 debug_object_active_state(head, &rcuhead_debug_descr, 85 STATE_RCU_HEAD_QUEUED, 86 STATE_RCU_HEAD_READY); 87 debug_object_deactivate(head, &rcuhead_debug_descr); 88 } 89 #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ 90 static inline int debug_rcu_head_queue(struct rcu_head *head) 91 { 92 return 0; 93 } 94 95 static inline void debug_rcu_head_unqueue(struct rcu_head *head) 96 { 97 } 98 #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ 99 100 void kfree(const void *); 101 102 /* 103 * Reclaim the specified callback, either by invoking it (non-lazy case) 104 * or freeing it directly (lazy case). Return true if lazy, false otherwise. 105 */ 106 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head) 107 { 108 unsigned long offset = (unsigned long)head->func; 109 110 rcu_lock_acquire(&rcu_callback_map); 111 if (__is_kfree_rcu_offset(offset)) { 112 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset)); 113 kfree((void *)head - offset); 114 rcu_lock_release(&rcu_callback_map); 115 return true; 116 } else { 117 RCU_TRACE(trace_rcu_invoke_callback(rn, head)); 118 head->func(head); 119 rcu_lock_release(&rcu_callback_map); 120 return false; 121 } 122 } 123 124 #ifdef CONFIG_RCU_STALL_COMMON 125 126 extern int rcu_cpu_stall_suppress; 127 int rcu_jiffies_till_stall_check(void); 128 129 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */ 130 131 /* 132 * Strings used in tracepoints need to be exported via the 133 * tracing system such that tools like perf and trace-cmd can 134 * translate the string address pointers to actual text. 135 */ 136 #define TPS(x) tracepoint_string(x) 137 138 void rcu_early_boot_tests(void); 139 140 #endif /* __LINUX_RCU_H */ 141