Line data    Source code

       1             : /* SPDX-License-Identifier: GPL-2.0+ */
       2             : /*
       3             :  * Sleepable Read-Copy Update mechanism for mutual exclusion,
       4             :  *      tiny variant.
       5             :  *
       6             :  * Copyright (C) IBM Corporation, 2017
       7             :  *
       8             :  * Author: Paul McKenney <paulmck@linux.ibm.com>
       9             :  */
      10             : 
      11             : #ifndef _LINUX_SRCU_TINY_H
      12             : #define _LINUX_SRCU_TINY_H
      13             : 
      14             : #include <linux/swait.h>
      15             : 
      16             : struct srcu_struct {
      17             :         short srcu_lock_nesting[2];     /* srcu_read_lock() nesting depth. */
      18             :         u8 srcu_gp_running;             /* GP workqueue running? */
      19             :         u8 srcu_gp_waiting;             /* GP waiting for readers? */
      20             :         unsigned long srcu_idx;         /* Current reader array element in bit 0x2. */
      21             :         unsigned long srcu_idx_max;     /* Furthest future srcu_idx request. */
      22             :         struct swait_queue_head srcu_wq;
      23             :                                         /* Last srcu_read_unlock() wakes GP. */
      24             :         struct rcu_head *srcu_cb_head;  /* Pending callbacks: Head. */
      25             :         struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */
      26             :         struct work_struct srcu_work;   /* For driving grace periods. */
      27             : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      28             :         struct lockdep_map dep_map;
      29             : #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
      30             : };
      31             : 
      32             : void srcu_drive_gp(struct work_struct *wp);
      33             : 
      34             : #define __SRCU_STRUCT_INIT(name, __ignored, ___ignored)                 \
      35             : {                                                                       \
      36             :         .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq),        \
      37             :         .srcu_cb_tail = &name.srcu_cb_head,                         \
      38             :         .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \
      39             :         __SRCU_DEP_MAP_INIT(name)                                       \
      40             : }
      41             : 
      42             : /*
      43             :  * This odd _STATIC_ arrangement is needed for API compatibility with
      44             :  * Tree SRCU, which needs some per-CPU data.
      45             :  */
      46             : #define DEFINE_SRCU(name) \
      47             :         struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
      48             : #define DEFINE_STATIC_SRCU(name) \
      49             :         static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
      50             : 
      51             : void synchronize_srcu(struct srcu_struct *ssp);
      52             : 
      53             : /*
      54             :  * Counts the new reader in the appropriate per-CPU element of the
      55             :  * srcu_struct.  Can be invoked from irq/bh handlers, but the matching
      56             :  * __srcu_read_unlock() must be in the same handler instance.  Returns an
      57             :  * index that must be passed to the matching srcu_read_unlock().
      58             :  */
      59             : static inline int __srcu_read_lock(struct srcu_struct *ssp)
      60             : {
      61             :         int idx;
      62             : 
      63        1997 :         idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
      64        1997 :         WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1);
      65             :         return idx;
      66             : }
      67             : 
      68             : static inline void synchronize_srcu_expedited(struct srcu_struct *ssp)
      69             : {
      70             :         synchronize_srcu(ssp);
      71             : }
      72             : 
      73             : static inline void srcu_barrier(struct srcu_struct *ssp)
      74             : {
      75             :         synchronize_srcu(ssp);
      76             : }
      77             : 
      78             : /* Defined here to avoid size increase for non-torture kernels. */
      79             : static inline void srcu_torture_stats_print(struct srcu_struct *ssp,
      80             :                                             char *tt, char *tf)
      81             : {
      82             :         int idx;
      83             : 
      84             :         idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1;
      85             :         pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd) gp: %lu->%lu\n",
      86             :                  tt, tf, idx,
      87             :                  data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])),
      88             :                  data_race(READ_ONCE(ssp->srcu_lock_nesting[idx])),
      89             :                  data_race(READ_ONCE(ssp->srcu_idx)),
      90             :                  data_race(READ_ONCE(ssp->srcu_idx_max)));
      91             : }
      92             : 
      93             : #endif