kernel/rcu/rcu_segcblist.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * RCU segmented callback lists, internal-to-rcu header file
   4  *
   5  * Copyright IBM Corporation, 2017
   6  *
   7  * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
   8  */
   9
  10 #include <linux/rcu_segcblist.h>
  11
  12 /* Return number of callbacks in the specified callback list. */
  13 static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp)
  14 {
  15         return READ_ONCE(rclp->len);
  16 }
  17
  18 /* Return number of callbacks in segmented callback list by summing seglen. */
  19 long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp);
  20
  21 void rcu_cblist_init(struct rcu_cblist *rclp);
  22 void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp);
  23 void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp,
  24                               struct rcu_cblist *srclp,
  25                               struct rcu_head *rhp);
  26 struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp);
  27
  28 /*
  29  * Is the specified rcu_segcblist structure empty?
  30  *
  31  * But careful!  The fact that the ->head field is NULL does not
  32  * necessarily imply that there are no callbacks associated with
  33  * this structure.  When callbacks are being invoked, they are
  34  * removed as a group.  If callback invocation must be preempted,
  35  * the remaining callbacks will be added back to the list.  Either
  36  * way, the counts are updated later.
  37  *
  38  * So it is often the case that rcu_segcblist_n_cbs() should be used
  39  * instead.
  40  */
  41 static inline bool rcu_segcblist_empty(struct rcu_segcblist *rsclp)
  42 {
  43         return !READ_ONCE(rsclp->head);
  44 }
  45
  46 /* Return number of callbacks in segmented callback list. */
  47 static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp)
  48 {
  49 #ifdef CONFIG_RCU_NOCB_CPU
  50         return atomic_long_read(&rsclp->len);
  51 #else
  52         return READ_ONCE(rsclp->len);
  53 #endif
  54 }
  55
  56 static inline void rcu_segcblist_set_flags(struct rcu_segcblist *rsclp,
  57                                            int flags)
  58 {
  59         rsclp->flags |= flags;
  60 }
  61
  62 static inline void rcu_segcblist_clear_flags(struct rcu_segcblist *rsclp,
  63                                              int flags)
  64 {
  65         rsclp->flags &= ~flags;
  66 }
  67
  68 static inline bool rcu_segcblist_test_flags(struct rcu_segcblist *rsclp,
  69                                             int flags)
  70 {
  71         return READ_ONCE(rsclp->flags) & flags;
  72 }
  73
  74 /*
  75  * Is the specified rcu_segcblist enabled, for example, not corresponding
  76  * to an offline CPU?
  77  */
  78 static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
  79 {
  80         return rcu_segcblist_test_flags(rsclp, SEGCBLIST_ENABLED);
  81 }
  82
  83 /* Is the specified rcu_segcblist offloaded, or is SEGCBLIST_SOFTIRQ_ONLY set? */
  84 static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
  85 {
  86         if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
  87             !rcu_segcblist_test_flags(rsclp, SEGCBLIST_SOFTIRQ_ONLY))
  88                 return true;
  89
  90         return false;
  91 }
  92
  93 static inline bool rcu_segcblist_completely_offloaded(struct rcu_segcblist *rsclp)
  94 {
  95         int flags = SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP | SEGCBLIST_OFFLOADED;
  96
  97         if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) && (rsclp->flags & flags) == flags)
  98                 return true;
  99
 100         return false;
 101 }
 102
 103 /*
 104  * Are all segments following the specified segment of the specified
 105  * rcu_segcblist structure empty of callbacks?  (The specified
 106  * segment might well contain callbacks.)
 107  */
 108 static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
 109 {
 110         return !READ_ONCE(*READ_ONCE(rsclp->tails[seg]));
 111 }
 112
 113 /*
 114  * Is the specified segment of the specified rcu_segcblist structure
 115  * empty of callbacks?
 116  */
 117 static inline bool rcu_segcblist_segempty(struct rcu_segcblist *rsclp, int seg)
 118 {
 119         if (seg == RCU_DONE_TAIL)
 120                 return &rsclp->head == rsclp->tails[RCU_DONE_TAIL];
 121         return rsclp->tails[seg - 1] == rsclp->tails[seg];
 122 }
 123
 124 void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp);
 125 void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v);
 126 void rcu_segcblist_init(struct rcu_segcblist *rsclp);
 127 void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
 128 void rcu_segcblist_offload(struct rcu_segcblist *rsclp, bool offload);
 129 bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
 130 bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
 131 struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
 132 struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp);
 133 bool rcu_segcblist_nextgp(struct rcu_segcblist *rsclp, unsigned long *lp);
 134 void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
 135                            struct rcu_head *rhp);
 136 bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
 137                            struct rcu_head *rhp);
 138 void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
 139                                     struct rcu_cblist *rclp);
 140 void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
 141                                     struct rcu_cblist *rclp);
 142 void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
 143                                 struct rcu_cblist *rclp);
 144 void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
 145                                    struct rcu_cblist *rclp);
 146 void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
 147                                    struct rcu_cblist *rclp);
 148 void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq);
 149 bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq);
 150 void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
 151                          struct rcu_segcblist *src_rsclp);