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