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/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Read-Copy Update definitions shared among RCU implementations.
*
* Copyright IBM Corporation, 2011
*
* Author: Paul E. McKenney <paulmck@linux.ibm.com>
*/
#ifndef __LINUX_RCU_H
#define __LINUX_RCU_H
#include <trace/events/rcu.h>
/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
#define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1)
/*
* 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;
}
/*
* 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;
}
/*
* 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);
}
/* 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);
}
/* Compute the end-of-grace-period value for the specified sequence number. */
static inline unsigned long rcu_seq_endval(unsigned long *sp)
{
return (*sp | RCU_SEQ_STATE_MASK) + 1;
}
/* 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, rcu_seq_endval(sp));
}
/*
* rcu_seq_snap - Take a snapshot of the update side's sequence number.
*
* This function returns the earliest value of the grace-period sequence number
* that will indicate that a full grace period has elapsed since the current
* time. Once the grace-period sequence number has reached this value, it will
* be safe to invoke all callbacks that have been registered prior to the
* current time. This value is the current grace-period number plus two to the
* power of the number of low-order bits reserved for state, then rounded up to
* the next value in which the state bits are all zero.
*/
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;
}
/* 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);
}
/*
* Given a snapshot from rcu_seq_snap(), determine whether or not the
* corresponding update-side operation has started.
*/
static inline bool rcu_seq_started(unsigned long *sp, unsigned long s)
{
return ULONG_CMP_LT((s - 1) & ~RCU_SEQ_STATE_MASK, READ_ONCE(*sp));
}
/*
* 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);
}
/*
* Has a grace period completed since the time the old gp_seq was collected?
*/
static inline bool rcu_seq_completed_gp(unsigned long old, unsigned long new)
{
return ULONG_CMP_LT(old, new & ~RCU_SEQ_STATE_MASK);
}
/*
* Has a grace period started since the time the old gp_seq was collected?
*/
static inline bool rcu_seq_new_gp(unsigned long old, unsigned long new)
{
return ULONG_CMP_LT((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK,
new);
}
/*
* Roughly how many full grace periods have elapsed between the collection
* of the two specified grace periods?
*/
static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
{
unsigned long rnd_diff;
if (old == new)
return 0;
/*
* Compute the number of grace periods (still shifted up), plus
* one if either of new and old is not an exact grace period.
*/
rnd_diff = (new & ~RCU_SEQ_STATE_MASK) -
((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK) +
((new & RCU_SEQ_STATE_MASK) || (old & RCU_SEQ_STATE_MASK));
if (ULONG_CMP_GE(RCU_SEQ_STATE_MASK, rnd_diff))
return 1; /* Definitely no grace period has elapsed. */
return ((rnd_diff - RCU_SEQ_STATE_MASK - 1) >> RCU_SEQ_CTR_SHIFT) + 2;
}
/*
* 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. These are in rcupdate.h because they are used by all
* RCU implementations.
*/
#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;
}
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);
}
#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
static inline int debug_rcu_head_queue(struct rcu_head *head)
{
return 0;
}
static inline void debug_rcu_head_unqueue(struct rcu_head *head)
{
}
#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)
{
rcu_callback_t f;
unsigned long offset = (unsigned long)head->func;
rcu_lock_acquire(&rcu_callback_map);
if (__is_kfree_rcu_offset(offset)) {
trace_rcu_invoke_kfree_callback(rn, head, offset);
kfree((void *)head - offset);
rcu_lock_release(&rcu_callback_map);
return true;
} else {
trace_rcu_invoke_callback(rn, head);
f = head->func;
WRITE_ONCE(head->func, (rcu_callback_t)0L);
f(head);
rcu_lock_release(&rcu_callback_map);
return false;
}
}
#ifdef CONFIG_RCU_STALL_COMMON
extern int rcu_cpu_stall_suppress;
extern int rcu_cpu_stall_timeout;
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
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