/*
- * Read-Copy Update mechanism for mutual exclusion
+ * Read-Copy Update mechanism for mutual exclusion
*
* 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
* Copyright IBM Corporation, 2001
*
* Author: Dipankar Sarma <dipankar@in.ibm.com>
- *
+ *
* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
* Papers:
* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
*
* For detailed explanation of Read-Copy Update mechanism see -
- * http://lse.sourceforge.net/locking/rcupdate.html
+ * http://lse.sourceforge.net/locking/rcupdate.html
*
*/
#include <linux/lockdep.h>
#include <linux/completion.h>
+#ifdef CONFIG_RCU_TORTURE_TEST
+extern int rcutorture_runnable; /* for sysctl */
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
+
/**
* struct rcu_head - callback structure for use with RCU
* @next: next update requests in a list
};
/* Exported common interfaces */
-extern void synchronize_rcu(void);
extern void synchronize_rcu_bh(void);
+extern void synchronize_sched(void);
extern void rcu_barrier(void);
extern void rcu_barrier_bh(void);
extern void rcu_barrier_sched(void);
/* Internal to kernel */
extern void rcu_init(void);
-extern void rcu_scheduler_starting(void);
-extern int rcu_needs_cpu(int cpu);
extern int rcu_scheduler_active;
+extern void rcu_scheduler_starting(void);
-#if defined(CONFIG_TREE_RCU)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
#include <linux/rcutree.h>
-#elif defined(CONFIG_PREEMPT_RCU)
-#include <linux/rcupreempt.h>
+#elif defined(CONFIG_TINY_RCU)
+#include <linux/rcutiny.h>
#else
#error "Unknown RCU implementation specified to kernel configuration"
-#endif /* #else #if defined(CONFIG_CLASSIC_RCU) */
+#endif
-#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
+#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
#define INIT_RCU_HEAD(ptr) do { \
(ptr)->next = NULL; (ptr)->func = NULL; \
} while (0)
#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
extern struct lockdep_map rcu_lock_map;
-# define rcu_read_acquire() \
- lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
+# define rcu_read_acquire() \
+ lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
-#else
-# define rcu_read_acquire() do { } while (0)
-# define rcu_read_release() do { } while (0)
-#endif
+
+extern struct lockdep_map rcu_bh_lock_map;
+# define rcu_read_acquire_bh() \
+ lock_acquire(&rcu_bh_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
+# define rcu_read_release_bh() lock_release(&rcu_bh_lock_map, 1, _THIS_IP_)
+
+extern struct lockdep_map rcu_sched_lock_map;
+# define rcu_read_acquire_sched() \
+ lock_acquire(&rcu_sched_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
+# define rcu_read_release_sched() \
+ lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
+
+static inline int debug_lockdep_rcu_enabled(void)
+{
+ return likely(rcu_scheduler_active && debug_locks);
+}
+
+/**
+ * rcu_read_lock_held - might we be in RCU read-side critical section?
+ *
+ * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in
+ * an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING,
+ * this assumes we are in an RCU read-side critical section unless it can
+ * prove otherwise.
+ *
+ * Check rcu_scheduler_active to prevent false positives during boot.
+ */
+static inline int rcu_read_lock_held(void)
+{
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ return lock_is_held(&rcu_lock_map);
+}
+
+/*
+ * rcu_read_lock_bh_held() is defined out of line to avoid #include-file
+ * hell.
+ */
+extern int rcu_read_lock_bh_held(void);
+
+/**
+ * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section?
+ *
+ * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in an
+ * RCU-sched read-side critical section. In absence of CONFIG_PROVE_LOCKING,
+ * this assumes we are in an RCU-sched read-side critical section unless it
+ * can prove otherwise. Note that disabling of preemption (including
+ * disabling irqs) counts as an RCU-sched read-side critical section.
+ *
+ * Check rcu_scheduler_active to prevent false positives during boot.
+ */
+#ifdef CONFIG_PREEMPT
+static inline int rcu_read_lock_sched_held(void)
+{
+ int lockdep_opinion = 0;
+
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ if (debug_locks)
+ lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
+ return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
+}
+#else /* #ifdef CONFIG_PREEMPT */
+static inline int rcu_read_lock_sched_held(void)
+{
+ return 1;
+}
+#endif /* #else #ifdef CONFIG_PREEMPT */
+
+#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+# define rcu_read_acquire() do { } while (0)
+# define rcu_read_release() do { } while (0)
+# define rcu_read_acquire_bh() do { } while (0)
+# define rcu_read_release_bh() do { } while (0)
+# define rcu_read_acquire_sched() do { } while (0)
+# define rcu_read_release_sched() do { } while (0)
+
+static inline int rcu_read_lock_held(void)
+{
+ return 1;
+}
+
+static inline int rcu_read_lock_bh_held(void)
+{
+ return 1;
+}
+
+#ifdef CONFIG_PREEMPT
+static inline int rcu_read_lock_sched_held(void)
+{
+ return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled();
+}
+#else /* #ifdef CONFIG_PREEMPT */
+static inline int rcu_read_lock_sched_held(void)
+{
+ return 1;
+}
+#endif /* #else #ifdef CONFIG_PREEMPT */
+
+#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+#ifdef CONFIG_PROVE_RCU
+
+/**
+ * rcu_dereference_check - rcu_dereference with debug checking
+ *
+ * Do an rcu_dereference(), but check that the context is correct.
+ * For example, rcu_dereference_check(gp, rcu_read_lock_held()) to
+ * ensure that the rcu_dereference_check() executes within an RCU
+ * read-side critical section. It is also possible to check for
+ * locks being held, for example, by using lockdep_is_held().
+ */
+#define rcu_dereference_check(p, c) \
+ ({ \
+ if (debug_lockdep_rcu_enabled() && !(c)) \
+ lockdep_rcu_dereference(__FILE__, __LINE__); \
+ rcu_dereference_raw(p); \
+ })
+
+#else /* #ifdef CONFIG_PROVE_RCU */
+
+#define rcu_dereference_check(p, c) rcu_dereference_raw(p)
+
+#endif /* #else #ifdef CONFIG_PROVE_RCU */
/**
* rcu_read_lock - mark the beginning of an RCU read-side critical section.
rcu_read_acquire();
}
-/**
- * rcu_read_unlock - marks the end of an RCU read-side critical section.
- *
- * See rcu_read_lock() for more information.
- */
-
/*
* So where is rcu_write_lock()? It does not exist, as there is no
* way for writers to lock out RCU readers. This is a feature, not
* used as well. RCU does not care how the writers keep out of each
* others' way, as long as they do so.
*/
+
+/**
+ * rcu_read_unlock - marks the end of an RCU read-side critical section.
+ *
+ * See rcu_read_lock() for more information.
+ */
static inline void rcu_read_unlock(void)
{
rcu_read_release();
{
__rcu_read_lock_bh();
__acquire(RCU_BH);
- rcu_read_acquire();
+ rcu_read_acquire_bh();
}
/*
*/
static inline void rcu_read_unlock_bh(void)
{
- rcu_read_release();
+ rcu_read_release_bh();
__release(RCU_BH);
__rcu_read_unlock_bh();
}
{
preempt_disable();
__acquire(RCU_SCHED);
- rcu_read_acquire();
+ rcu_read_acquire_sched();
}
-static inline void rcu_read_lock_sched_notrace(void)
+
+/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
+static inline notrace void rcu_read_lock_sched_notrace(void)
{
preempt_disable_notrace();
__acquire(RCU_SCHED);
- rcu_read_acquire();
}
/*
*/
static inline void rcu_read_unlock_sched(void)
{
- rcu_read_release();
+ rcu_read_release_sched();
__release(RCU_SCHED);
preempt_enable();
}
-static inline void rcu_read_unlock_sched_notrace(void)
+
+/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */
+static inline notrace void rcu_read_unlock_sched_notrace(void)
{
- rcu_read_release();
__release(RCU_SCHED);
preempt_enable_notrace();
}
/**
- * rcu_dereference - fetch an RCU-protected pointer in an
- * RCU read-side critical section. This pointer may later
- * be safely dereferenced.
+ * rcu_dereference_raw - fetch an RCU-protected pointer
+ *
+ * The caller must be within some flavor of RCU read-side critical
+ * section, or must be otherwise preventing the pointer from changing,
+ * for example, by holding an appropriate lock. This pointer may later
+ * be safely dereferenced. It is the caller's responsibility to have
+ * done the right thing, as this primitive does no checking of any kind.
*
* Inserts memory barriers on architectures that require them
* (currently only the Alpha), and, more importantly, documents
* exactly which pointers are protected by RCU.
*/
-
-#define rcu_dereference(p) ({ \
+#define rcu_dereference_raw(p) ({ \
typeof(p) _________p1 = ACCESS_ONCE(p); \
smp_read_barrier_depends(); \
(_________p1); \
})
/**
+ * rcu_dereference - fetch an RCU-protected pointer, checking for RCU
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference(p) \
+ rcu_dereference_check(p, rcu_read_lock_held())
+
+/**
+ * rcu_dereference_bh - fetch an RCU-protected pointer, checking for RCU-bh
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference_bh(p) \
+ rcu_dereference_check(p, rcu_read_lock_bh_held())
+
+/**
+ * rcu_dereference_sched - fetch RCU-protected pointer, checking for RCU-sched
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference_sched(p) \
+ rcu_dereference_check(p, rcu_read_lock_sched_held())
+
+/**
* rcu_assign_pointer - assign (publicize) a pointer to a newly
* initialized structure that will be dereferenced by RCU read-side
* critical sections. Returns the value assigned.
extern void wakeme_after_rcu(struct rcu_head *head);
/**
- * synchronize_sched - block until all CPUs have exited any non-preemptive
- * kernel code sequences.
- *
- * This means that all preempt_disable code sequences, including NMI and
- * hardware-interrupt handlers, in progress on entry will have completed
- * before this primitive returns. However, this does not guarantee that
- * softirq handlers will have completed, since in some kernels, these
- * handlers can run in process context, and can block.
- *
- * This primitive provides the guarantees made by the (now removed)
- * synchronize_kernel() API. In contrast, synchronize_rcu() only
- * guarantees that rcu_read_lock() sections will have completed.
- * In "classic RCU", these two guarantees happen to be one and
- * the same, but can differ in realtime RCU implementations.
- */
-#define synchronize_sched() __synchronize_sched()
-
-/**
* call_rcu - Queue an RCU callback for invocation after a grace period.
* @head: structure to be used for queueing the RCU updates.
* @func: actual update function to be invoked after the grace period