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891cd1f99d
Currently, variables used only within lockdep expressions are flagged as unused, requiring that these variables' declarations be decorated with either #ifdef or __maybe_unused. This results in ugly code. This commit therefore causes the RCU lock maps to be visible even when lockdep is not enabled, thus removing the need for these decorations. This approach further relies on dead-code elimination to remove any references to functions or variables that are not available in non-lockdep kernels. Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
99 lines
3.1 KiB
C
99 lines
3.1 KiB
C
/* 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, int nesting);
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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);
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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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rcu_read_unlock_trace_special(t, nesting);
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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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