cregit-Linux how code gets into the kernel

Release 4.15 kernel/rcu/rcu.h

Directory: kernel/rcu
/*
 * Read-Copy Update definitions shared among RCU implementations.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you can access it online at
 * http://www.gnu.org/licenses/gpl-2.0.html.
 *
 * Copyright IBM Corporation, 2011
 *
 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 */

#ifndef __LINUX_RCU_H

#define __LINUX_RCU_H

#include <trace/events/rcu.h>
#ifdef CONFIG_RCU_TRACE

#define RCU_TRACE(stmt) stmt
#else /* #ifdef CONFIG_RCU_TRACE */

#define RCU_TRACE(stmt)
#endif /* #else #ifdef CONFIG_RCU_TRACE */

/*
 * Process-level increment to ->dynticks_nesting field.  This allows for
 * architectures that use half-interrupts and half-exceptions from
 * process context.
 *
 * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH
 * that counts the number of process-based reasons why RCU cannot
 * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE
 * is the value used to increment or decrement this field.
 *
 * The rest of the bits could in principle be used to count interrupts,
 * but this would mean that a negative-one value in the interrupt
 * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field.
 * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK
 * that is set to DYNTICK_TASK_FLAG upon initial exit from idle.
 * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon
 * initial exit from idle.
 */

#define DYNTICK_TASK_NEST_WIDTH 7

#define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1)

#define DYNTICK_TASK_NEST_MASK  (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1)

#define DYNTICK_TASK_FLAG	   ((DYNTICK_TASK_NEST_VALUE / 8) * 2)

#define DYNTICK_TASK_MASK	   ((DYNTICK_TASK_NEST_VALUE / 8) * 3)

#define DYNTICK_TASK_EXIT_IDLE	   (DYNTICK_TASK_NEST_VALUE + \
                                    DYNTICK_TASK_FLAG)


/*
 * Grace-period counter management.
 */


#define RCU_SEQ_CTR_SHIFT	2

#define RCU_SEQ_STATE_MASK	((1 << RCU_SEQ_CTR_SHIFT) - 1)

/*
 * Return the counter portion of a sequence number previously returned
 * by rcu_seq_snap() or rcu_seq_current().
 */

static inline unsigned long rcu_seq_ctr(unsigned long s) { return s >> RCU_SEQ_CTR_SHIFT; }

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/* * Return the state portion of a sequence number previously returned * by rcu_seq_snap() or rcu_seq_current(). */
static inline int rcu_seq_state(unsigned long s) { return s & RCU_SEQ_STATE_MASK; }

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/* * Set the state portion of the pointed-to sequence number. * The caller is responsible for preventing conflicting updates. */
static inline void rcu_seq_set_state(unsigned long *sp, int newstate) { WARN_ON_ONCE(newstate & ~RCU_SEQ_STATE_MASK); WRITE_ONCE(*sp, (*sp & ~RCU_SEQ_STATE_MASK) + newstate); }

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/* Adjust sequence number for start of update-side operation. */
static inline void rcu_seq_start(unsigned long *sp) { WRITE_ONCE(*sp, *sp + 1); smp_mb(); /* Ensure update-side operation after counter increment. */ WARN_ON_ONCE(rcu_seq_state(*sp) != 1); }

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/* Adjust sequence number for end of update-side operation. */
static inline void rcu_seq_end(unsigned long *sp) { smp_mb(); /* Ensure update-side operation before counter increment. */ WARN_ON_ONCE(!rcu_seq_state(*sp)); WRITE_ONCE(*sp, (*sp | RCU_SEQ_STATE_MASK) + 1); }

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/* Take a snapshot of the update side's sequence number. */
static inline unsigned long rcu_seq_snap(unsigned long *sp) { unsigned long s; s = (READ_ONCE(*sp) + 2 * RCU_SEQ_STATE_MASK + 1) & ~RCU_SEQ_STATE_MASK; smp_mb(); /* Above access must not bleed into critical section. */ return s; }

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/* Return the current value the update side's sequence number, no ordering. */
static inline unsigned long rcu_seq_current(unsigned long *sp) { return READ_ONCE(*sp); }

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/* * Given a snapshot from rcu_seq_snap(), determine whether or not a * full update-side operation has occurred. */
static inline bool rcu_seq_done(unsigned long *sp, unsigned long s) { return ULONG_CMP_GE(READ_ONCE(*sp), s); }

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/* * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally * by call_rcu() and rcu callback execution, and are therefore not part of the * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors. */ #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD # define STATE_RCU_HEAD_READY 0 # define STATE_RCU_HEAD_QUEUED 1 extern struct debug_obj_descr rcuhead_debug_descr;
static inline int debug_rcu_head_queue(struct rcu_head *head) { int r1; r1 = debug_object_activate(head, &rcuhead_debug_descr); debug_object_active_state(head, &rcuhead_debug_descr, STATE_RCU_HEAD_READY, STATE_RCU_HEAD_QUEUED); return r1; }

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static inline void debug_rcu_head_unqueue(struct rcu_head *head) { debug_object_active_state(head, &rcuhead_debug_descr, STATE_RCU_HEAD_QUEUED, STATE_RCU_HEAD_READY); debug_object_deactivate(head, &rcuhead_debug_descr); }

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#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
static inline int debug_rcu_head_queue(struct rcu_head *head) { return 0; }

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static inline void debug_rcu_head_unqueue(struct rcu_head *head) { }

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#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ void kfree(const void *); /* * Reclaim the specified callback, either by invoking it (non-lazy case) * or freeing it directly (lazy case). Return true if lazy, false otherwise. */
static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head) { unsigned long offset = (unsigned long)head->func; rcu_lock_acquire(&rcu_callback_map); if (__is_kfree_rcu_offset(offset)) { RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);) kfree((void *)head - offset); rcu_lock_release(&rcu_callback_map); return true; } else { RCU_TRACE(trace_rcu_invoke_callback(rn, head);) head->func(head); rcu_lock_release(&rcu_callback_map); return false; } }

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#ifdef CONFIG_RCU_STALL_COMMON extern int rcu_cpu_stall_suppress; int rcu_jiffies_till_stall_check(void); #define rcu_ftrace_dump_stall_suppress() \ do { \ if (!rcu_cpu_stall_suppress) \ rcu_cpu_stall_suppress = 3; \ } while (0) #define rcu_ftrace_dump_stall_unsuppress() \ do { \ if (rcu_cpu_stall_suppress == 3) \ rcu_cpu_stall_suppress = 0; \ } while (0) #else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */ #define rcu_ftrace_dump_stall_suppress() #define rcu_ftrace_dump_stall_unsuppress() #endif /* #ifdef CONFIG_RCU_STALL_COMMON */ /* * Strings used in tracepoints need to be exported via the * tracing system such that tools like perf and trace-cmd can * translate the string address pointers to actual text. */ #define TPS(x) tracepoint_string(x) /* * Dump the ftrace buffer, but only one time per callsite per boot. */ #define rcu_ftrace_dump(oops_dump_mode) \ do { \ static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \ \ if (!atomic_read(&___rfd_beenhere) && \ !atomic_xchg(&___rfd_beenhere, 1)) { \ tracing_off(); \ rcu_ftrace_dump_stall_suppress(); \ ftrace_dump(oops_dump_mode); \ rcu_ftrace_dump_stall_unsuppress(); \ } \ } while (0) void rcu_early_boot_tests(void); void rcu_test_sync_prims(void); /* * This function really isn't for public consumption, but RCU is special in * that context switches can allow the state machine to make progress. */ extern void resched_cpu(int cpu); #if defined(SRCU) || !defined(TINY_RCU) #include <linux/rcu_node_tree.h> extern int rcu_num_lvls; extern int num_rcu_lvl[]; extern int rcu_num_nodes; static bool rcu_fanout_exact; static int rcu_fanout_leaf; /* * Compute the per-level fanout, either using the exact fanout specified * or balancing the tree, depending on the rcu_fanout_exact boot parameter. */
static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) { int i; if (rcu_fanout_exact) { levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf; for (i = rcu_num_lvls - 2; i >= 0; i--) levelspread[i] = RCU_FANOUT; } else { int ccur; int cprv; cprv = nr_cpu_ids; for (i = rcu_num_lvls - 1; i >= 0; i--) { ccur = levelcnt[i]; levelspread[i] = (cprv + ccur - 1) / ccur; cprv = ccur; } } }

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/* * Do a full breadth-first scan of the rcu_node structures for the * specified rcu_state structure. */ #define rcu_for_each_node_breadth_first(rsp, rnp) \ for ((rnp) = &(rsp)->node[0]; \ (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) /* * Do a breadth-first scan of the non-leaf rcu_node structures for the * specified rcu_state structure. Note that if there is a singleton * rcu_node tree with but one rcu_node structure, this loop is a no-op. */ #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \ for ((rnp) = &(rsp)->node[0]; \ (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++) /* * Scan the leaves of the rcu_node hierarchy for the specified rcu_state * structure. Note that if there is a singleton rcu_node tree with but * one rcu_node structure, this loop -will- visit the rcu_node structure. * It is still a leaf node, even if it is also the root node. */ #define rcu_for_each_leaf_node(rsp, rnp) \ for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \ (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) /* * Iterate over all possible CPUs in a leaf RCU node. */ #define for_each_leaf_node_possible_cpu(rnp, cpu) \ for ((cpu) = cpumask_next(rnp->grplo - 1, cpu_possible_mask); \ cpu <= rnp->grphi; \ cpu = cpumask_next((cpu), cpu_possible_mask)) /* * Wrappers for the rcu_node::lock acquire and release. * * Because the rcu_nodes form a tree, the tree traversal locking will observe * different lock values, this in turn means that an UNLOCK of one level * followed by a LOCK of another level does not imply a full memory barrier; * and most importantly transitivity is lost. * * In order to restore full ordering between tree levels, augment the regular * lock acquire functions with smp_mb__after_unlock_lock(). * * As ->lock of struct rcu_node is a __private field, therefore one should use * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock. */ #define raw_spin_lock_rcu_node(p) \ do { \ raw_spin_lock(&ACCESS_PRIVATE(p, lock)); \ smp_mb__after_unlock_lock(); \ } while (0) #define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock)) #define raw_spin_lock_irq_rcu_node(p) \ do { \ raw_spin_lock_irq(&ACCESS_PRIVATE(p, lock)); \ smp_mb__after_unlock_lock(); \ } while (0) #define raw_spin_unlock_irq_rcu_node(p) \ raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock)) #define raw_spin_lock_irqsave_rcu_node(p, flags) \ do { \ raw_spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \ smp_mb__after_unlock_lock(); \ } while (0) #define raw_spin_unlock_irqrestore_rcu_node(p, flags) \ raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags) \ #define raw_spin_trylock_rcu_node(p) \ ({ \ bool ___locked = raw_spin_trylock(&ACCESS_PRIVATE(p, lock)); \ \ if (___locked) \ smp_mb__after_unlock_lock(); \ ___locked; \ }) #endif /* #if defined(SRCU) || !defined(TINY_RCU) */ #ifdef CONFIG_TINY_RCU /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
static inline bool rcu_gp_is_normal(void) { return true; }

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static inline bool rcu_gp_is_expedited(void) { return false; }

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static inline void rcu_expedite_gp(void) { }

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static inline void rcu_unexpedite_gp(void) { }

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#else /* #ifdef CONFIG_TINY_RCU */ bool rcu_gp_is_normal(void); /* Internal RCU use. */ bool rcu_gp_is_expedited(void); /* Internal RCU use. */ void rcu_expedite_gp(void); void rcu_unexpedite_gp(void); void rcupdate_announce_bootup_oddness(void); #endif /* #else #ifdef CONFIG_TINY_RCU */ #define RCU_SCHEDULER_INACTIVE 0 #define RCU_SCHEDULER_INIT 1 #define RCU_SCHEDULER_RUNNING 2 #ifdef CONFIG_TINY_RCU
static inline void rcu_request_urgent_qs_task(struct task_struct *t) { }

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#else /* #ifdef CONFIG_TINY_RCU */ void rcu_request_urgent_qs_task(struct task_struct *t); #endif /* #else #ifdef CONFIG_TINY_RCU */ enum rcutorture_type { RCU_FLAVOR, RCU_BH_FLAVOR, RCU_SCHED_FLAVOR, RCU_TASKS_FLAVOR, SRCU_FLAVOR, INVALID_RCU_FLAVOR }; #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, unsigned long *gpnum, unsigned long *completed); void rcutorture_record_test_transition(void); void rcutorture_record_progress(unsigned long vernum); void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, unsigned long c_old, unsigned long c); #else
static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, unsigned long *gpnum, unsigned long *completed) { *flags = 0; *gpnum = 0; *completed = 0; }

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static inline void rcutorture_record_test_transition(void) { }

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static inline void rcutorture_record_progress(unsigned long vernum) { }

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#ifdef CONFIG_RCU_TRACE void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, unsigned long c_old, unsigned long c); #else #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ do { } while (0) #endif #endif #ifdef CONFIG_TINY_SRCU
static inline void srcutorture_get_gp_data(enum rcutorture_type test_type, struct srcu_struct *sp, int *flags, unsigned long *gpnum, unsigned long *completed) { if (test_type != SRCU_FLAVOR) return; *flags = 0; *completed = sp->srcu_idx; *gpnum = *completed; }

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#elif defined(CONFIG_TREE_SRCU) void srcutorture_get_gp_data(enum rcutorture_type test_type, struct srcu_struct *sp, int *flags, unsigned long *gpnum, unsigned long *completed); #endif #ifdef CONFIG_TINY_RCU
static inline unsigned long rcu_batches_started(void) { return 0; }

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static inline unsigned long rcu_batches_started_bh(void) { return 0; }

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static inline unsigned long rcu_batches_started_sched(void) { return 0; }

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static inline unsigned long rcu_batches_completed(void) { return 0; }

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static inline unsigned long rcu_batches_completed_bh(void) { return 0; }

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static inline unsigned long rcu_batches_completed_sched(void) { return 0; }

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static inline unsigned long rcu_exp_batches_completed(void) { return 0; }

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static inline unsigned long rcu_exp_batches_completed_sched(void) { return 0; }

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static inline unsigned long srcu_batches_completed(struct srcu_struct *sp) { return 0; }

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static inline void rcu_force_quiescent_state(void) { }

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static inline void rcu_bh_force_quiescent_state(void) { }

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static inline void rcu_sched_force_quiescent_state(void) { }

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static inline void show_rcu_gp_kthreads(void) { }

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#else /* #ifdef CONFIG_TINY_RCU */ extern unsigned long rcutorture_testseq; extern unsigned long rcutorture_vernum; unsigned long rcu_batches_started(void); unsigned long rcu_batches_started_bh(void); unsigned long rcu_batches_started_sched(void); unsigned long rcu_batches_completed(void); unsigned long rcu_batches_completed_bh(void); unsigned long rcu_batches_completed_sched(void); unsigned long rcu_exp_batches_completed(void); unsigned long rcu_exp_batches_completed_sched(void); unsigned long srcu_batches_completed(struct srcu_struct *sp); void show_rcu_gp_kthreads(void); void rcu_force_quiescent_state(void); void rcu_bh_force_quiescent_state(void); void rcu_sched_force_quiescent_state(void); #endif /* #else #ifdef CONFIG_TINY_RCU */ #ifdef CONFIG_RCU_NOCB_CPU bool rcu_is_nocb_cpu(int cpu); #else
static inline bool rcu_is_nocb_cpu(int cpu) { return false; }

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#endif #endif /* __LINUX_RCU_H */

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Steven Rostedt10.06%12.50%
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Directory: kernel/rcu
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