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Diffstat (limited to 'ANDROID_3.4.5/include/linux/rcupdate.h')
| -rw-r--r-- | ANDROID_3.4.5/include/linux/rcupdate.h | 951 |
1 files changed, 0 insertions, 951 deletions
diff --git a/ANDROID_3.4.5/include/linux/rcupdate.h b/ANDROID_3.4.5/include/linux/rcupdate.h deleted file mode 100644 index 20fb776a..00000000 --- a/ANDROID_3.4.5/include/linux/rcupdate.h +++ /dev/null @@ -1,951 +0,0 @@ -/* - * 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 - * 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, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * 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://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf - * 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 - * - */ - -#ifndef __LINUX_RCUPDATE_H -#define __LINUX_RCUPDATE_H - -#include <linux/types.h> -#include <linux/cache.h> -#include <linux/spinlock.h> -#include <linux/threads.h> -#include <linux/cpumask.h> -#include <linux/seqlock.h> -#include <linux/lockdep.h> -#include <linux/completion.h> -#include <linux/debugobjects.h> -#include <linux/bug.h> -#include <linux/compiler.h> - -#ifdef CONFIG_RCU_TORTURE_TEST -extern int rcutorture_runnable; /* for sysctl */ -#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ - -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) -extern void rcutorture_record_test_transition(void); -extern void rcutorture_record_progress(unsigned long vernum); -extern void do_trace_rcu_torture_read(char *rcutorturename, - struct rcu_head *rhp); -#else -static inline void rcutorture_record_test_transition(void) -{ -} -static inline void rcutorture_record_progress(unsigned long vernum) -{ -} -#ifdef CONFIG_RCU_TRACE -extern void do_trace_rcu_torture_read(char *rcutorturename, - struct rcu_head *rhp); -#else -#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) -#endif -#endif - -#define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) -#define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) -#define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) -#define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) - -/* Exported common interfaces */ - -#ifdef CONFIG_PREEMPT_RCU - -/** - * call_rcu() - Queue an RCU callback for invocation after a grace period. - * @head: structure to be used for queueing the RCU updates. - * @func: actual callback function to be invoked after the grace period - * - * The callback function will be invoked some time after a full grace - * period elapses, in other words after all pre-existing RCU read-side - * critical sections have completed. However, the callback function - * might well execute concurrently with RCU read-side critical sections - * that started after call_rcu() was invoked. RCU read-side critical - * sections are delimited by rcu_read_lock() and rcu_read_unlock(), - * and may be nested. - */ -extern void call_rcu(struct rcu_head *head, - void (*func)(struct rcu_head *head)); - -#else /* #ifdef CONFIG_PREEMPT_RCU */ - -/* In classic RCU, call_rcu() is just call_rcu_sched(). */ -#define call_rcu call_rcu_sched - -#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ - -/** - * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. - * @head: structure to be used for queueing the RCU updates. - * @func: actual callback function to be invoked after the grace period - * - * The callback function will be invoked some time after a full grace - * period elapses, in other words after all currently executing RCU - * read-side critical sections have completed. call_rcu_bh() assumes - * that the read-side critical sections end on completion of a softirq - * handler. This means that read-side critical sections in process - * context must not be interrupted by softirqs. This interface is to be - * used when most of the read-side critical sections are in softirq context. - * RCU read-side critical sections are delimited by : - * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. - * OR - * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. - * These may be nested. - */ -extern void call_rcu_bh(struct rcu_head *head, - void (*func)(struct rcu_head *head)); - -/** - * call_rcu_sched() - Queue an RCU for invocation after sched grace period. - * @head: structure to be used for queueing the RCU updates. - * @func: actual callback function to be invoked after the grace period - * - * The callback function will be invoked some time after a full grace - * period elapses, in other words after all currently executing RCU - * read-side critical sections have completed. call_rcu_sched() assumes - * that the read-side critical sections end on enabling of preemption - * or on voluntary preemption. - * RCU read-side critical sections are delimited by : - * - rcu_read_lock_sched() and rcu_read_unlock_sched(), - * OR - * anything that disables preemption. - * These may be nested. - */ -extern void call_rcu_sched(struct rcu_head *head, - void (*func)(struct rcu_head *rcu)); - -extern void synchronize_sched(void); - -#ifdef CONFIG_PREEMPT_RCU - -extern void __rcu_read_lock(void); -extern void __rcu_read_unlock(void); -void synchronize_rcu(void); - -/* - * Defined as a macro as it is a very low level header included from - * areas that don't even know about current. This gives the rcu_read_lock() - * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other - * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. - */ -#define rcu_preempt_depth() (current->rcu_read_lock_nesting) - -#else /* #ifdef CONFIG_PREEMPT_RCU */ - -static inline void __rcu_read_lock(void) -{ - preempt_disable(); -} - -static inline void __rcu_read_unlock(void) -{ - preempt_enable(); -} - -static inline void synchronize_rcu(void) -{ - synchronize_sched(); -} - -static inline int rcu_preempt_depth(void) -{ - return 0; -} - -#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ - -/* Internal to kernel */ -extern void rcu_sched_qs(int cpu); -extern void rcu_bh_qs(int cpu); -extern void rcu_check_callbacks(int cpu, int user); -struct notifier_block; -extern void rcu_idle_enter(void); -extern void rcu_idle_exit(void); -extern void rcu_irq_enter(void); -extern void rcu_irq_exit(void); - -/** - * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers - * @a: Code that RCU needs to pay attention to. - * - * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden - * in the inner idle loop, that is, between the rcu_idle_enter() and - * the rcu_idle_exit() -- RCU will happily ignore any such read-side - * critical sections. However, things like powertop need tracepoints - * in the inner idle loop. - * - * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) - * will tell RCU that it needs to pay attending, invoke its argument - * (in this example, a call to the do_something_with_RCU() function), - * and then tell RCU to go back to ignoring this CPU. It is permissible - * to nest RCU_NONIDLE() wrappers, but the nesting level is currently - * quite limited. If deeper nesting is required, it will be necessary - * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. - * - * This macro may be used from process-level code only. - */ -#define RCU_NONIDLE(a) \ - do { \ - rcu_idle_exit(); \ - do { a; } while (0); \ - rcu_idle_enter(); \ - } while (0) - -/* - * Infrastructure to implement the synchronize_() primitives in - * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. - */ - -typedef void call_rcu_func_t(struct rcu_head *head, - void (*func)(struct rcu_head *head)); -void wait_rcu_gp(call_rcu_func_t crf); - -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) -#include <linux/rcutree.h> -#elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU) -#include <linux/rcutiny.h> -#else -#error "Unknown RCU implementation specified to kernel configuration" -#endif - -/* - * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic - * initialization and destruction of rcu_head on the stack. rcu_head structures - * allocated dynamically in the heap or defined statically don't need any - * initialization. - */ -#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD -extern void init_rcu_head_on_stack(struct rcu_head *head); -extern void destroy_rcu_head_on_stack(struct rcu_head *head); -#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ -static inline void init_rcu_head_on_stack(struct rcu_head *head) -{ -} - -static inline void destroy_rcu_head_on_stack(struct rcu_head *head) -{ -} -#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ - -#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) -bool rcu_lockdep_current_cpu_online(void); -#else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ -static inline bool rcu_lockdep_current_cpu_online(void) -{ - return 1; -} -#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ - -#ifdef CONFIG_DEBUG_LOCK_ALLOC - -#ifdef CONFIG_PROVE_RCU -extern int rcu_is_cpu_idle(void); -#else /* !CONFIG_PROVE_RCU */ -static inline int rcu_is_cpu_idle(void) -{ - return 0; -} -#endif /* else !CONFIG_PROVE_RCU */ - -static inline void rcu_lock_acquire(struct lockdep_map *map) -{ - lock_acquire(map, 0, 0, 2, 1, NULL, _THIS_IP_); -} - -static inline void rcu_lock_release(struct lockdep_map *map) -{ - lock_release(map, 1, _THIS_IP_); -} - -extern struct lockdep_map rcu_lock_map; -extern struct lockdep_map rcu_bh_lock_map; -extern struct lockdep_map rcu_sched_lock_map; -extern int debug_lockdep_rcu_enabled(void); - -/** - * rcu_read_lock_held() - might we be in RCU read-side critical section? - * - * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU - * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, - * this assumes we are in an RCU read-side critical section unless it can - * prove otherwise. This is useful for debug checks in functions that - * require that they be called within an RCU read-side critical section. - * - * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot - * and while lockdep is disabled. - * - * Note that rcu_read_lock() and the matching rcu_read_unlock() must - * occur in the same context, for example, it is illegal to invoke - * rcu_read_unlock() in process context if the matching rcu_read_lock() - * was invoked from within an irq handler. - * - * Note that rcu_read_lock() is disallowed if the CPU is either idle or - * offline from an RCU perspective, so check for those as well. - */ -static inline int rcu_read_lock_held(void) -{ - if (!debug_lockdep_rcu_enabled()) - return 1; - if (rcu_is_cpu_idle()) - return 0; - if (!rcu_lockdep_current_cpu_online()) - return 0; - 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_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an - * RCU-sched read-side critical section. In absence of - * CONFIG_DEBUG_LOCK_ALLOC, 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. This is useful for debug checks in functions - * that required that they be called within an RCU-sched read-side - * critical section. - * - * Check debug_lockdep_rcu_enabled() to prevent false positives during boot - * and while lockdep is disabled. - * - * Note that if the CPU is in the idle loop from an RCU point of - * view (ie: that we are in the section between rcu_idle_enter() and - * rcu_idle_exit()) then rcu_read_lock_held() returns false even if the CPU - * did an rcu_read_lock(). The reason for this is that RCU ignores CPUs - * that are in such a section, considering these as in extended quiescent - * state, so such a CPU is effectively never in an RCU read-side critical - * section regardless of what RCU primitives it invokes. This state of - * affairs is required --- we need to keep an RCU-free window in idle - * where the CPU may possibly enter into low power mode. This way we can - * notice an extended quiescent state to other CPUs that started a grace - * period. Otherwise we would delay any grace period as long as we run in - * the idle task. - * - * Similarly, we avoid claiming an SRCU read lock held if the current - * CPU is offline. - */ -#ifdef CONFIG_PREEMPT_COUNT -static inline int rcu_read_lock_sched_held(void) -{ - int lockdep_opinion = 0; - - if (!debug_lockdep_rcu_enabled()) - return 1; - if (rcu_is_cpu_idle()) - return 0; - if (!rcu_lockdep_current_cpu_online()) - return 0; - if (debug_locks) - lockdep_opinion = lock_is_held(&rcu_sched_lock_map); - return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); -} -#else /* #ifdef CONFIG_PREEMPT_COUNT */ -static inline int rcu_read_lock_sched_held(void) -{ - return 1; -} -#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ - -#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ - -# define rcu_lock_acquire(a) do { } while (0) -# define rcu_lock_release(a) 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_COUNT -static inline int rcu_read_lock_sched_held(void) -{ - return preempt_count() != 0 || irqs_disabled(); -} -#else /* #ifdef CONFIG_PREEMPT_COUNT */ -static inline int rcu_read_lock_sched_held(void) -{ - return 1; -} -#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ - -#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ - -#ifdef CONFIG_PROVE_RCU - -extern int rcu_my_thread_group_empty(void); - -/** - * rcu_lockdep_assert - emit lockdep splat if specified condition not met - * @c: condition to check - * @s: informative message - */ -#define rcu_lockdep_assert(c, s) \ - do { \ - static bool __section(.data.unlikely) __warned; \ - if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ - __warned = true; \ - lockdep_rcu_suspicious(__FILE__, __LINE__, s); \ - } \ - } while (0) - -#if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU) -static inline void rcu_preempt_sleep_check(void) -{ - rcu_lockdep_assert(!lock_is_held(&rcu_lock_map), - "Illegal context switch in RCU read-side " - "critical section"); -} -#else /* #ifdef CONFIG_PROVE_RCU */ -static inline void rcu_preempt_sleep_check(void) -{ -} -#endif /* #else #ifdef CONFIG_PROVE_RCU */ - -#define rcu_sleep_check() \ - do { \ - rcu_preempt_sleep_check(); \ - rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \ - "Illegal context switch in RCU-bh" \ - " read-side critical section"); \ - rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \ - "Illegal context switch in RCU-sched"\ - " read-side critical section"); \ - } while (0) - -#else /* #ifdef CONFIG_PROVE_RCU */ - -#define rcu_lockdep_assert(c, s) do { } while (0) -#define rcu_sleep_check() do { } while (0) - -#endif /* #else #ifdef CONFIG_PROVE_RCU */ - -/* - * Helper functions for rcu_dereference_check(), rcu_dereference_protected() - * and rcu_assign_pointer(). Some of these could be folded into their - * callers, but they are left separate in order to ease introduction of - * multiple flavors of pointers to match the multiple flavors of RCU - * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in - * the future. - */ - -#ifdef __CHECKER__ -#define rcu_dereference_sparse(p, space) \ - ((void)(((typeof(*p) space *)p) == p)) -#else /* #ifdef __CHECKER__ */ -#define rcu_dereference_sparse(p, space) -#endif /* #else #ifdef __CHECKER__ */ - -#define __rcu_access_pointer(p, space) \ - ({ \ - typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ - rcu_dereference_sparse(p, space); \ - ((typeof(*p) __force __kernel *)(_________p1)); \ - }) -#define __rcu_dereference_check(p, c, space) \ - ({ \ - typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ - rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \ - " usage"); \ - rcu_dereference_sparse(p, space); \ - smp_read_barrier_depends(); \ - ((typeof(*p) __force __kernel *)(_________p1)); \ - }) -#define __rcu_dereference_protected(p, c, space) \ - ({ \ - rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \ - " usage"); \ - rcu_dereference_sparse(p, space); \ - ((typeof(*p) __force __kernel *)(p)); \ - }) - -#define __rcu_access_index(p, space) \ - ({ \ - typeof(p) _________p1 = ACCESS_ONCE(p); \ - rcu_dereference_sparse(p, space); \ - (_________p1); \ - }) -#define __rcu_dereference_index_check(p, c) \ - ({ \ - typeof(p) _________p1 = ACCESS_ONCE(p); \ - rcu_lockdep_assert(c, \ - "suspicious rcu_dereference_index_check()" \ - " usage"); \ - smp_read_barrier_depends(); \ - (_________p1); \ - }) -#define __rcu_assign_pointer(p, v, space) \ - ({ \ - smp_wmb(); \ - (p) = (typeof(*v) __force space *)(v); \ - }) - - -/** - * rcu_access_pointer() - fetch RCU pointer with no dereferencing - * @p: The pointer to read - * - * Return the value of the specified RCU-protected pointer, but omit the - * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful - * when the value of this pointer is accessed, but the pointer is not - * dereferenced, for example, when testing an RCU-protected pointer against - * NULL. Although rcu_access_pointer() may also be used in cases where - * update-side locks prevent the value of the pointer from changing, you - * should instead use rcu_dereference_protected() for this use case. - * - * It is also permissible to use rcu_access_pointer() when read-side - * access to the pointer was removed at least one grace period ago, as - * is the case in the context of the RCU callback that is freeing up - * the data, or after a synchronize_rcu() returns. This can be useful - * when tearing down multi-linked structures after a grace period - * has elapsed. - */ -#define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) - -/** - * rcu_dereference_check() - rcu_dereference with debug checking - * @p: The pointer to read, prior to dereferencing - * @c: The conditions under which the dereference will take place - * - * Do an rcu_dereference(), but check that the conditions under which the - * dereference will take place are correct. Typically the conditions - * indicate the various locking conditions that should be held at that - * point. The check should return true if the conditions are satisfied. - * An implicit check for being in an RCU read-side critical section - * (rcu_read_lock()) is included. - * - * For example: - * - * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock)); - * - * could be used to indicate to lockdep that foo->bar may only be dereferenced - * if either rcu_read_lock() is held, or that the lock required to replace - * the bar struct at foo->bar is held. - * - * Note that the list of conditions may also include indications of when a lock - * need not be held, for example during initialisation or destruction of the - * target struct: - * - * bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) || - * atomic_read(&foo->usage) == 0); - * - * Inserts memory barriers on architectures that require them - * (currently only the Alpha), prevents the compiler from refetching - * (and from merging fetches), and, more importantly, documents exactly - * which pointers are protected by RCU and checks that the pointer is - * annotated as __rcu. - */ -#define rcu_dereference_check(p, c) \ - __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu) - -/** - * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking - * @p: The pointer to read, prior to dereferencing - * @c: The conditions under which the dereference will take place - * - * This is the RCU-bh counterpart to rcu_dereference_check(). - */ -#define rcu_dereference_bh_check(p, c) \ - __rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu) - -/** - * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking - * @p: The pointer to read, prior to dereferencing - * @c: The conditions under which the dereference will take place - * - * This is the RCU-sched counterpart to rcu_dereference_check(). - */ -#define rcu_dereference_sched_check(p, c) \ - __rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \ - __rcu) - -#define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ - -/** - * rcu_access_index() - fetch RCU index with no dereferencing - * @p: The index to read - * - * Return the value of the specified RCU-protected index, but omit the - * smp_read_barrier_depends() and keep the ACCESS_ONCE(). This is useful - * when the value of this index is accessed, but the index is not - * dereferenced, for example, when testing an RCU-protected index against - * -1. Although rcu_access_index() may also be used in cases where - * update-side locks prevent the value of the index from changing, you - * should instead use rcu_dereference_index_protected() for this use case. - */ -#define rcu_access_index(p) __rcu_access_index((p), __rcu) - -/** - * rcu_dereference_index_check() - rcu_dereference for indices with debug checking - * @p: The pointer to read, prior to dereferencing - * @c: The conditions under which the dereference will take place - * - * Similar to rcu_dereference_check(), but omits the sparse checking. - * This allows rcu_dereference_index_check() to be used on integers, - * which can then be used as array indices. Attempting to use - * rcu_dereference_check() on an integer will give compiler warnings - * because the sparse address-space mechanism relies on dereferencing - * the RCU-protected pointer. Dereferencing integers is not something - * that even gcc will put up with. - * - * Note that this function does not implicitly check for RCU read-side - * critical sections. If this function gains lots of uses, it might - * make sense to provide versions for each flavor of RCU, but it does - * not make sense as of early 2010. - */ -#define rcu_dereference_index_check(p, c) \ - __rcu_dereference_index_check((p), (c)) - -/** - * rcu_dereference_protected() - fetch RCU pointer when updates prevented - * @p: The pointer to read, prior to dereferencing - * @c: The conditions under which the dereference will take place - * - * Return the value of the specified RCU-protected pointer, but omit - * both the smp_read_barrier_depends() and the ACCESS_ONCE(). This - * is useful in cases where update-side locks prevent the value of the - * pointer from changing. Please note that this primitive does -not- - * prevent the compiler from repeating this reference or combining it - * with other references, so it should not be used without protection - * of appropriate locks. - * - * This function is only for update-side use. Using this function - * when protected only by rcu_read_lock() will result in infrequent - * but very ugly failures. - */ -#define rcu_dereference_protected(p, c) \ - __rcu_dereference_protected((p), (c), __rcu) - - -/** - * rcu_dereference() - fetch RCU-protected pointer for dereferencing - * @p: The pointer to read, prior to dereferencing - * - * This is a simple wrapper around rcu_dereference_check(). - */ -#define rcu_dereference(p) rcu_dereference_check(p, 0) - -/** - * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing - * @p: The pointer to read, prior to dereferencing - * - * Makes rcu_dereference_check() do the dirty work. - */ -#define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0) - -/** - * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing - * @p: The pointer to read, prior to dereferencing - * - * Makes rcu_dereference_check() do the dirty work. - */ -#define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) - -/** - * rcu_read_lock() - mark the beginning of an RCU read-side critical section - * - * When synchronize_rcu() is invoked on one CPU while other CPUs - * are within RCU read-side critical sections, then the - * synchronize_rcu() is guaranteed to block until after all the other - * CPUs exit their critical sections. Similarly, if call_rcu() is invoked - * on one CPU while other CPUs are within RCU read-side critical - * sections, invocation of the corresponding RCU callback is deferred - * until after the all the other CPUs exit their critical sections. - * - * Note, however, that RCU callbacks are permitted to run concurrently - * with new RCU read-side critical sections. One way that this can happen - * is via the following sequence of events: (1) CPU 0 enters an RCU - * read-side critical section, (2) CPU 1 invokes call_rcu() to register - * an RCU callback, (3) CPU 0 exits the RCU read-side critical section, - * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU - * callback is invoked. This is legal, because the RCU read-side critical - * section that was running concurrently with the call_rcu() (and which - * therefore might be referencing something that the corresponding RCU - * callback would free up) has completed before the corresponding - * RCU callback is invoked. - * - * RCU read-side critical sections may be nested. Any deferred actions - * will be deferred until the outermost RCU read-side critical section - * completes. - * - * You can avoid reading and understanding the next paragraph by - * following this rule: don't put anything in an rcu_read_lock() RCU - * read-side critical section that would block in a !PREEMPT kernel. - * But if you want the full story, read on! - * - * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), it - * is illegal to block while in an RCU read-side critical section. In - * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU) - * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may - * be preempted, but explicit blocking is illegal. Finally, in preemptible - * RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds, - * RCU read-side critical sections may be preempted and they may also - * block, but only when acquiring spinlocks that are subject to priority - * inheritance. - */ -static inline void rcu_read_lock(void) -{ - __rcu_read_lock(); - __acquire(RCU); - rcu_lock_acquire(&rcu_lock_map); - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "rcu_read_lock() used illegally while idle"); -} - -/* - * 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 - * a bug -- this property is what provides RCU's performance benefits. - * Of course, writers must coordinate with each other. The normal - * spinlock primitives work well for this, but any other technique may be - * 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_lockdep_assert(!rcu_is_cpu_idle(), - "rcu_read_unlock() used illegally while idle"); - rcu_lock_release(&rcu_lock_map); - __release(RCU); - __rcu_read_unlock(); -} - -/** - * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section - * - * This is equivalent of rcu_read_lock(), but to be used when updates - * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since - * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a - * softirq handler to be a quiescent state, a process in RCU read-side - * critical section must be protected by disabling softirqs. Read-side - * critical sections in interrupt context can use just rcu_read_lock(), - * though this should at least be commented to avoid confusing people - * reading the code. - * - * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() - * must occur in the same context, for example, it is illegal to invoke - * rcu_read_unlock_bh() from one task if the matching rcu_read_lock_bh() - * was invoked from some other task. - */ -static inline void rcu_read_lock_bh(void) -{ - local_bh_disable(); - __acquire(RCU_BH); - rcu_lock_acquire(&rcu_bh_lock_map); - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "rcu_read_lock_bh() used illegally while idle"); -} - -/* - * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section - * - * See rcu_read_lock_bh() for more information. - */ -static inline void rcu_read_unlock_bh(void) -{ - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "rcu_read_unlock_bh() used illegally while idle"); - rcu_lock_release(&rcu_bh_lock_map); - __release(RCU_BH); - local_bh_enable(); -} - -/** - * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section - * - * This is equivalent of rcu_read_lock(), but to be used when updates - * are being done using call_rcu_sched() or synchronize_rcu_sched(). - * Read-side critical sections can also be introduced by anything that - * disables preemption, including local_irq_disable() and friends. - * - * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() - * must occur in the same context, for example, it is illegal to invoke - * rcu_read_unlock_sched() from process context if the matching - * rcu_read_lock_sched() was invoked from an NMI handler. - */ -static inline void rcu_read_lock_sched(void) -{ - preempt_disable(); - __acquire(RCU_SCHED); - rcu_lock_acquire(&rcu_sched_lock_map); - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "rcu_read_lock_sched() used illegally while idle"); -} - -/* 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_unlock_sched - marks the end of a RCU-classic critical section - * - * See rcu_read_lock_sched for more information. - */ -static inline void rcu_read_unlock_sched(void) -{ - rcu_lockdep_assert(!rcu_is_cpu_idle(), - "rcu_read_unlock_sched() used illegally while idle"); - rcu_lock_release(&rcu_sched_lock_map); - __release(RCU_SCHED); - preempt_enable(); -} - -/* Used by lockdep and tracing: cannot be traced, cannot call lockdep. */ -static inline notrace void rcu_read_unlock_sched_notrace(void) -{ - __release(RCU_SCHED); - preempt_enable_notrace(); -} - -/** - * rcu_assign_pointer() - assign to RCU-protected pointer - * @p: pointer to assign to - * @v: value to assign (publish) - * - * Assigns the specified value to the specified RCU-protected - * pointer, ensuring that any concurrent RCU readers will see - * any prior initialization. Returns the value assigned. - * - * Inserts memory barriers on architectures that require them - * (which is most of them), and also prevents the compiler from - * reordering the code that initializes the structure after the pointer - * assignment. More importantly, this call documents which pointers - * will be dereferenced by RCU read-side code. - * - * In some special cases, you may use RCU_INIT_POINTER() instead - * of rcu_assign_pointer(). RCU_INIT_POINTER() is a bit faster due - * to the fact that it does not constrain either the CPU or the compiler. - * That said, using RCU_INIT_POINTER() when you should have used - * rcu_assign_pointer() is a very bad thing that results in - * impossible-to-diagnose memory corruption. So please be careful. - * See the RCU_INIT_POINTER() comment header for details. - */ -#define rcu_assign_pointer(p, v) \ - __rcu_assign_pointer((p), (v), __rcu) - -/** - * RCU_INIT_POINTER() - initialize an RCU protected pointer - * - * Initialize an RCU-protected pointer in special cases where readers - * do not need ordering constraints on the CPU or the compiler. These - * special cases are: - * - * 1. This use of RCU_INIT_POINTER() is NULLing out the pointer -or- - * 2. The caller has taken whatever steps are required to prevent - * RCU readers from concurrently accessing this pointer -or- - * 3. The referenced data structure has already been exposed to - * readers either at compile time or via rcu_assign_pointer() -and- - * a. You have not made -any- reader-visible changes to - * this structure since then -or- - * b. It is OK for readers accessing this structure from its - * new location to see the old state of the structure. (For - * example, the changes were to statistical counters or to - * other state where exact synchronization is not required.) - * - * Failure to follow these rules governing use of RCU_INIT_POINTER() will - * result in impossible-to-diagnose memory corruption. As in the structures - * will look OK in crash dumps, but any concurrent RCU readers might - * see pre-initialized values of the referenced data structure. So - * please be very careful how you use RCU_INIT_POINTER()!!! - * - * If you are creating an RCU-protected linked structure that is accessed - * by a single external-to-structure RCU-protected pointer, then you may - * use RCU_INIT_POINTER() to initialize the internal RCU-protected - * pointers, but you must use rcu_assign_pointer() to initialize the - * external-to-structure pointer -after- you have completely initialized - * the reader-accessible portions of the linked structure. - */ -#define RCU_INIT_POINTER(p, v) \ - p = (typeof(*v) __force __rcu *)(v) - -static __always_inline bool __is_kfree_rcu_offset(unsigned long offset) -{ - return offset < 4096; -} - -static __always_inline -void __kfree_rcu(struct rcu_head *head, unsigned long offset) -{ - typedef void (*rcu_callback)(struct rcu_head *); - - BUILD_BUG_ON(!__builtin_constant_p(offset)); - - /* See the kfree_rcu() header comment. */ - BUILD_BUG_ON(!__is_kfree_rcu_offset(offset)); - - kfree_call_rcu(head, (rcu_callback)offset); -} - -/** - * kfree_rcu() - kfree an object after a grace period. - * @ptr: pointer to kfree - * @rcu_head: the name of the struct rcu_head within the type of @ptr. - * - * Many rcu callbacks functions just call kfree() on the base structure. - * These functions are trivial, but their size adds up, and furthermore - * when they are used in a kernel module, that module must invoke the - * high-latency rcu_barrier() function at module-unload time. - * - * The kfree_rcu() function handles this issue. Rather than encoding a - * function address in the embedded rcu_head structure, kfree_rcu() instead - * encodes the offset of the rcu_head structure within the base structure. - * Because the functions are not allowed in the low-order 4096 bytes of - * kernel virtual memory, offsets up to 4095 bytes can be accommodated. - * If the offset is larger than 4095 bytes, a compile-time error will - * be generated in __kfree_rcu(). If this error is triggered, you can - * either fall back to use of call_rcu() or rearrange the structure to - * position the rcu_head structure into the first 4096 bytes. - * - * Note that the allowable offset might decrease in the future, for example, - * to allow something like kmem_cache_free_rcu(). - */ -#define kfree_rcu(ptr, rcu_head) \ - __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) - -#endif /* __LINUX_RCUPDATE_H */ |