name : rcupdate_trace.h /* SPDX-License-Identifier: GPL-2.0+ */ /* * Read-Copy Update mechanism for mutual exclusion, adapted for tracing. * * Copyright (C) 2020 Paul E. McKenney. */ #ifndef __LINUX_RCUPDATE_TRACE_H #define __LINUX_RCUPDATE_TRACE_H #include <linux/sched.h> #include <linux/rcupdate.h> extern struct lockdep_map rcu_trace_lock_map; #ifdef CONFIG_DEBUG_LOCK_ALLOC static inline int rcu_read_lock_trace_held(void) { return lock_is_held(&rcu_trace_lock_map); } #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ static inline int rcu_read_lock_trace_held(void) { return 1; } #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ #ifdef CONFIG_TASKS_TRACE_RCU void rcu_read_unlock_trace_special(struct task_struct *t); /** * rcu_read_lock_trace - mark beginning of RCU-trace read-side critical section * * When synchronize_rcu_tasks_trace() is invoked by one task, then that * task is guaranteed to block until all other tasks exit their read-side * critical sections. Similarly, if call_rcu_trace() is invoked on one * task while other tasks are within RCU read-side critical sections, * invocation of the corresponding RCU callback is deferred until after * the all the other tasks exit their critical sections. * * For more details, please see the documentation for rcu_read_lock(). */ static inline void rcu_read_lock_trace(void) { struct task_struct *t = current; WRITE_ONCE(t->trc_reader_nesting, READ_ONCE(t->trc_reader_nesting) + 1); barrier(); if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) && t->trc_reader_special.b.need_mb) smp_mb(); // Pairs with update-side barriers rcu_lock_acquire(&rcu_trace_lock_map); } /** * rcu_read_unlock_trace - mark end of RCU-trace read-side critical section * * Pairs with a preceding call to rcu_read_lock_trace(), and nesting is * allowed. Invoking a rcu_read_unlock_trace() when there is no matching * rcu_read_lock_trace() is verboten, and will result in lockdep complaints. * * For more details, please see the documentation for rcu_read_unlock(). */ static inline void rcu_read_unlock_trace(void) { int nesting; struct task_struct *t = current; rcu_lock_release(&rcu_trace_lock_map); nesting = READ_ONCE(t->trc_reader_nesting) - 1; barrier(); // Critical section before disabling. // Disable IPI-based setting of .need_qs. WRITE_ONCE(t->trc_reader_nesting, INT_MIN + nesting); if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) { WRITE_ONCE(t->trc_reader_nesting, nesting); return; // We assume shallow reader nesting. } WARN_ON_ONCE(nesting != 0); rcu_read_unlock_trace_special(t); } void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func); void synchronize_rcu_tasks_trace(void); void rcu_barrier_tasks_trace(void); struct task_struct *get_rcu_tasks_trace_gp_kthread(void); #else /* * The BPF JIT forms these addresses even when it doesn't call these * functions, so provide definitions that result in runtime errors. */ static inline void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func) { BUG(); } static inline void rcu_read_lock_trace(void) { BUG(); } static inline void rcu_read_unlock_trace(void) { BUG(); } #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */ #endif /* __LINUX_RCUPDATE_TRACE_H */