1d5f177d3SPaul E. McKenney /* SPDX-License-Identifier: GPL-2.0+ */
2d5f177d3SPaul E. McKenney /*
3d5f177d3SPaul E. McKenney * Read-Copy Update mechanism for mutual exclusion, adapted for tracing.
4d5f177d3SPaul E. McKenney *
5d5f177d3SPaul E. McKenney * Copyright (C) 2020 Paul E. McKenney.
6d5f177d3SPaul E. McKenney */
7d5f177d3SPaul E. McKenney
8d5f177d3SPaul E. McKenney #ifndef __LINUX_RCUPDATE_TRACE_H
9d5f177d3SPaul E. McKenney #define __LINUX_RCUPDATE_TRACE_H
10d5f177d3SPaul E. McKenney
11d5f177d3SPaul E. McKenney #include <linux/sched.h>
12d5f177d3SPaul E. McKenney #include <linux/rcupdate.h>
13d5f177d3SPaul E. McKenney
14d5f177d3SPaul E. McKenney extern struct lockdep_map rcu_trace_lock_map;
15d5f177d3SPaul E. McKenney
16891cd1f9SJakub Kicinski #ifdef CONFIG_DEBUG_LOCK_ALLOC
17891cd1f9SJakub Kicinski
rcu_read_lock_trace_held(void)18d5f177d3SPaul E. McKenney static inline int rcu_read_lock_trace_held(void)
19d5f177d3SPaul E. McKenney {
20d5f177d3SPaul E. McKenney return lock_is_held(&rcu_trace_lock_map);
21d5f177d3SPaul E. McKenney }
22d5f177d3SPaul E. McKenney
23d5f177d3SPaul E. McKenney #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
24d5f177d3SPaul E. McKenney
rcu_read_lock_trace_held(void)25d5f177d3SPaul E. McKenney static inline int rcu_read_lock_trace_held(void)
26d5f177d3SPaul E. McKenney {
27d5f177d3SPaul E. McKenney return 1;
28d5f177d3SPaul E. McKenney }
29d5f177d3SPaul E. McKenney
30d5f177d3SPaul E. McKenney #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
31d5f177d3SPaul E. McKenney
32d5f177d3SPaul E. McKenney #ifdef CONFIG_TASKS_TRACE_RCU
33d5f177d3SPaul E. McKenney
34a5c071ccSPaul E. McKenney void rcu_read_unlock_trace_special(struct task_struct *t);
35d5f177d3SPaul E. McKenney
36d5f177d3SPaul E. McKenney /**
37d5f177d3SPaul E. McKenney * rcu_read_lock_trace - mark beginning of RCU-trace read-side critical section
38d5f177d3SPaul E. McKenney *
39c7dcf810SPaul E. McKenney * When synchronize_rcu_tasks_trace() is invoked by one task, then that
40c7dcf810SPaul E. McKenney * task is guaranteed to block until all other tasks exit their read-side
41d5f177d3SPaul E. McKenney * critical sections. Similarly, if call_rcu_trace() is invoked on one
42d5f177d3SPaul E. McKenney * task while other tasks are within RCU read-side critical sections,
43d5f177d3SPaul E. McKenney * invocation of the corresponding RCU callback is deferred until after
44d5f177d3SPaul E. McKenney * the all the other tasks exit their critical sections.
45d5f177d3SPaul E. McKenney *
46d5f177d3SPaul E. McKenney * For more details, please see the documentation for rcu_read_lock().
47d5f177d3SPaul E. McKenney */
rcu_read_lock_trace(void)48d5f177d3SPaul E. McKenney static inline void rcu_read_lock_trace(void)
49d5f177d3SPaul E. McKenney {
50d5f177d3SPaul E. McKenney struct task_struct *t = current;
51d5f177d3SPaul E. McKenney
52d5f177d3SPaul E. McKenney WRITE_ONCE(t->trc_reader_nesting, READ_ONCE(t->trc_reader_nesting) + 1);
53ba3a86e4SPaul E. McKenney barrier();
549ae58d7bSPaul E. McKenney if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) &&
559ae58d7bSPaul E. McKenney t->trc_reader_special.b.need_mb)
56276c4104SPaul E. McKenney smp_mb(); // Pairs with update-side barriers
57d5f177d3SPaul E. McKenney rcu_lock_acquire(&rcu_trace_lock_map);
58d5f177d3SPaul E. McKenney }
59d5f177d3SPaul E. McKenney
60d5f177d3SPaul E. McKenney /**
61d5f177d3SPaul E. McKenney * rcu_read_unlock_trace - mark end of RCU-trace read-side critical section
62d5f177d3SPaul E. McKenney *
63d5f177d3SPaul E. McKenney * Pairs with a preceding call to rcu_read_lock_trace(), and nesting is
64d5f177d3SPaul E. McKenney * allowed. Invoking a rcu_read_unlock_trace() when there is no matching
65d5f177d3SPaul E. McKenney * rcu_read_lock_trace() is verboten, and will result in lockdep complaints.
66d5f177d3SPaul E. McKenney *
67d5f177d3SPaul E. McKenney * For more details, please see the documentation for rcu_read_unlock().
68d5f177d3SPaul E. McKenney */
rcu_read_unlock_trace(void)69d5f177d3SPaul E. McKenney static inline void rcu_read_unlock_trace(void)
70d5f177d3SPaul E. McKenney {
71d5f177d3SPaul E. McKenney int nesting;
72d5f177d3SPaul E. McKenney struct task_struct *t = current;
73d5f177d3SPaul E. McKenney
74d5f177d3SPaul E. McKenney rcu_lock_release(&rcu_trace_lock_map);
75d5f177d3SPaul E. McKenney nesting = READ_ONCE(t->trc_reader_nesting) - 1;
76ba3a86e4SPaul E. McKenney barrier(); // Critical section before disabling.
77ba3a86e4SPaul E. McKenney // Disable IPI-based setting of .need_qs.
780356d4e6SPaul E. McKenney WRITE_ONCE(t->trc_reader_nesting, INT_MIN + nesting);
79276c4104SPaul E. McKenney if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) {
80d5f177d3SPaul E. McKenney WRITE_ONCE(t->trc_reader_nesting, nesting);
81d5f177d3SPaul E. McKenney return; // We assume shallow reader nesting.
82276c4104SPaul E. McKenney }
83a5c071ccSPaul E. McKenney WARN_ON_ONCE(nesting != 0);
84a5c071ccSPaul E. McKenney rcu_read_unlock_trace_special(t);
85d5f177d3SPaul E. McKenney }
86d5f177d3SPaul E. McKenney
87d5f177d3SPaul E. McKenney void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);
88d5f177d3SPaul E. McKenney void synchronize_rcu_tasks_trace(void);
89d5f177d3SPaul E. McKenney void rcu_barrier_tasks_trace(void);
90*5f8e3202SPaul E. McKenney struct task_struct *get_rcu_tasks_trace_gp_kthread(void);
919667305cSAlexei Starovoitov #else
929667305cSAlexei Starovoitov /*
939667305cSAlexei Starovoitov * The BPF JIT forms these addresses even when it doesn't call these
949667305cSAlexei Starovoitov * functions, so provide definitions that result in runtime errors.
959667305cSAlexei Starovoitov */
call_rcu_tasks_trace(struct rcu_head * rhp,rcu_callback_t func)969667305cSAlexei Starovoitov static inline void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func) { BUG(); }
rcu_read_lock_trace(void)979667305cSAlexei Starovoitov static inline void rcu_read_lock_trace(void) { BUG(); }
rcu_read_unlock_trace(void)989667305cSAlexei Starovoitov static inline void rcu_read_unlock_trace(void) { BUG(); }
99d5f177d3SPaul E. McKenney #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
100d5f177d3SPaul E. McKenney
101d5f177d3SPaul E. McKenney #endif /* __LINUX_RCUPDATE_TRACE_H */
102