include/linux/rcupdate_trace.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2 /*
   3  * Read-Copy Update mechanism for mutual exclusion, adapted for tracing.
   4  *
   5  * Copyright (C) 2020 Paul E. McKenney.
   6  */
   7
   8 #ifndef __LINUX_RCUPDATE_TRACE_H
   9 #define __LINUX_RCUPDATE_TRACE_H
  10
  11 #include <linux/sched.h>
  12 #include <linux/rcupdate.h>
  13
  14 extern struct lockdep_map rcu_trace_lock_map;
  15
  16 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  17
  18 static inline int rcu_read_lock_trace_held(void)
  19 {
  20         return lock_is_held(&rcu_trace_lock_map);
  21 }
  22
  23 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  24
  25 static inline int rcu_read_lock_trace_held(void)
  26 {
  27         return 1;
  28 }
  29
  30 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  31
  32 #ifdef CONFIG_TASKS_TRACE_RCU
  33
  34 void rcu_read_unlock_trace_special(struct task_struct *t, int nesting);
  35
  36 /**
  37  * rcu_read_lock_trace - mark beginning of RCU-trace read-side critical section
  38  *
  39  * When synchronize_rcu_tasks_trace() is invoked by one task, then that
  40  * task is guaranteed to block until all other tasks exit their read-side
  41  * critical sections.  Similarly, if call_rcu_trace() is invoked on one
  42  * task while other tasks are within RCU read-side critical sections,
  43  * invocation of the corresponding RCU callback is deferred until after
  44  * the all the other tasks exit their critical sections.
  45  *
  46  * For more details, please see the documentation for rcu_read_lock().
  47  */
  48 static inline void rcu_read_lock_trace(void)
  49 {
  50         struct task_struct *t = current;
  51
  52         WRITE_ONCE(t->trc_reader_nesting, READ_ONCE(t->trc_reader_nesting) + 1);
  53         barrier();
  54         if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) &&
  55             t->trc_reader_special.b.need_mb)
  56                 smp_mb(); // Pairs with update-side barriers
  57         rcu_lock_acquire(&rcu_trace_lock_map);
  58 }
  59
  60 /**
  61  * rcu_read_unlock_trace - mark end of RCU-trace read-side critical section
  62  *
  63  * Pairs with a preceding call to rcu_read_lock_trace(), and nesting is
  64  * allowed.  Invoking a rcu_read_unlock_trace() when there is no matching
  65  * rcu_read_lock_trace() is verboten, and will result in lockdep complaints.
  66  *
  67  * For more details, please see the documentation for rcu_read_unlock().
  68  */
  69 static inline void rcu_read_unlock_trace(void)
  70 {
  71         int nesting;
  72         struct task_struct *t = current;
  73
  74         rcu_lock_release(&rcu_trace_lock_map);
  75         nesting = READ_ONCE(t->trc_reader_nesting) - 1;
  76         barrier(); // Critical section before disabling.
  77         // Disable IPI-based setting of .need_qs.
  78         WRITE_ONCE(t->trc_reader_nesting, INT_MIN);
  79         if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) {
  80                 WRITE_ONCE(t->trc_reader_nesting, nesting);
  81                 return;  // We assume shallow reader nesting.
  82         }
  83         rcu_read_unlock_trace_special(t, nesting);
  84 }
  85
  86 void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);
  87 void synchronize_rcu_tasks_trace(void);
  88 void rcu_barrier_tasks_trace(void);
  89 #else
  90 /*
  91  * The BPF JIT forms these addresses even when it doesn't call these
  92  * functions, so provide definitions that result in runtime errors.
  93  */
  94 static inline void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func) { BUG(); }
  95 static inline void rcu_read_lock_trace(void) { BUG(); }
  96 static inline void rcu_read_unlock_trace(void) { BUG(); }
  97 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
  98
  99 #endif /* __LINUX_RCUPDATE_TRACE_H */