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/* 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, int nesting);
/**
* 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);
if (likely(!READ_ONCE(t->trc_reader_special.s)) || nesting) {
WRITE_ONCE(t->trc_reader_nesting, nesting);
return; // We assume shallow reader nesting.
}
rcu_read_unlock_trace_special(t, nesting);
}
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);
#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 */
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