diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/compiler.h | 4 | ||||
| -rw-r--r-- | include/linux/rcupdate.h | 352 | ||||
| -rw-r--r-- | include/linux/srcu.h | 27 |
3 files changed, 240 insertions, 143 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index c1a62c56a66..320d6c94ff8 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -16,7 +16,11 @@ # define __release(x) __context__(x,-1) # define __cond_lock(x,c) ((c) ? ({ __acquire(x); 1; }) : 0) # define __percpu __attribute__((noderef, address_space(3))) +#ifdef CONFIG_SPARSE_RCU_POINTER +# define __rcu __attribute__((noderef, address_space(4))) +#else # define __rcu +#endif extern void __chk_user_ptr(const volatile void __user *); extern void __chk_io_ptr(const volatile void __iomem *); #else diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 9fbc54a2585..b973dea2d6b 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -41,6 +41,7 @@ #include <linux/lockdep.h> #include <linux/completion.h> #include <linux/debugobjects.h> +#include <linux/compiler.h> #ifdef CONFIG_RCU_TORTURE_TEST extern int rcutorture_runnable; /* for sysctl */ @@ -120,14 +121,15 @@ 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? + * 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. + * prove otherwise. This is useful for debug checks in functions that + * require that they be called within an RCU read-side critical section. * - * Check debug_lockdep_rcu_enabled() to prevent false positives during boot + * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot * and while lockdep is disabled. */ static inline int rcu_read_lock_held(void) @@ -144,14 +146,16 @@ static inline int rcu_read_lock_held(void) extern int rcu_read_lock_bh_held(void); /** - * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section? + * 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. + * 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. @@ -220,41 +224,155 @@ extern int rcu_my_thread_group_empty(void); } \ } while (0) +#else /* #ifdef CONFIG_PROVE_RCU */ + +#define __do_rcu_dereference_check(c) 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. + */ +#define __rcu_access_pointer(p, space) \ + ({ \ + typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ + (void) (((typeof (*p) space *)p) == p); \ + ((typeof(*p) __force __kernel *)(_________p1)); \ + }) +#define __rcu_dereference_check(p, c, space) \ + ({ \ + typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \ + __do_rcu_dereference_check(c); \ + (void) (((typeof (*p) space *)p) == p); \ + smp_read_barrier_depends(); \ + ((typeof(*p) __force __kernel *)(_________p1)); \ + }) +#define __rcu_dereference_protected(p, c, space) \ + ({ \ + __do_rcu_dereference_check(c); \ + (void) (((typeof (*p) space *)p) == p); \ + ((typeof(*p) __force __kernel *)(p)); \ + }) + +#define __rcu_dereference_index_check(p, c) \ + ({ \ + typeof(p) _________p1 = ACCESS_ONCE(p); \ + __do_rcu_dereference_check(c); \ + smp_read_barrier_depends(); \ + (_________p1); \ + }) +#define __rcu_assign_pointer(p, v, space) \ + ({ \ + if (!__builtin_constant_p(v) || \ + ((v) != NULL)) \ + 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. + */ +#define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) + /** - * rcu_dereference_check - rcu_dereference with debug checking + * 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. + * 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, rcu_read_lock_held() || - * lockdep_is_held(&foo->lock)); + * 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 the RCU read lock is held, or that the lock required to replace + * 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, rcu_read_lock_held() || - * lockdep_is_held(&foo->lock) || + * 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) \ - ({ \ - __do_rcu_dereference_check(c); \ - rcu_dereference_raw(p); \ - }) + __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_protected - fetch RCU pointer when updates prevented + * 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_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 @@ -263,35 +381,61 @@ extern int rcu_my_thread_group_empty(void); * 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) \ - ({ \ - __do_rcu_dereference_check(c); \ - (p); \ - }) + __rcu_dereference_protected((p), (c), __rcu) -#else /* #ifdef CONFIG_PROVE_RCU */ +/** + * rcu_dereference_bh_protected() - fetch RCU-bh pointer when updates prevented + * @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_protected(). + */ +#define rcu_dereference_bh_protected(p, c) \ + __rcu_dereference_protected((p), (c), __rcu) -#define rcu_dereference_check(p, c) rcu_dereference_raw(p) -#define rcu_dereference_protected(p, c) (p) +/** + * rcu_dereference_sched_protected() - fetch RCU-sched pointer when updates prevented + * @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_protected(). + */ +#define rcu_dereference_sched_protected(p, c) \ + __rcu_dereference_protected((p), (c), __rcu) -#endif /* #else #ifdef CONFIG_PROVE_RCU */ /** - * rcu_access_pointer - fetch RCU pointer with no dereferencing + * rcu_dereference() - fetch RCU-protected pointer for dereferencing + * @p: The pointer to read, prior to dereferencing * - * 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. This may also be used in cases where update-side locks prevent - * the value of the pointer from changing, but rcu_dereference_protected() - * is a lighter-weight primitive for this use case. + * This is a simple wrapper around rcu_dereference_check(). */ -#define rcu_access_pointer(p) ACCESS_ONCE(p) +#define rcu_dereference(p) rcu_dereference_check(p, 0) /** - * rcu_read_lock - mark the beginning of an RCU read-side critical section. + * 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 @@ -337,7 +481,7 @@ static inline void rcu_read_lock(void) */ /** - * rcu_read_unlock - marks the end of an RCU read-side critical section. + * rcu_read_unlock() - marks the end of an RCU read-side critical section. * * See rcu_read_lock() for more information. */ @@ -349,15 +493,16 @@ static inline void rcu_read_unlock(void) } /** - * rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section + * 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(). Since call_rcu_bh() callbacks - * 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(). - * + * 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. */ static inline void rcu_read_lock_bh(void) { @@ -379,13 +524,12 @@ static inline void rcu_read_unlock_bh(void) } /** - * rcu_read_lock_sched - mark the beginning of a RCU-classic critical section + * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section * - * Should be used with either - * - synchronize_sched() - * or - * - call_rcu_sched() and rcu_barrier_sched() - * on the write-side to insure proper synchronization. + * 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. */ static inline void rcu_read_lock_sched(void) { @@ -420,54 +564,14 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) preempt_enable_notrace(); } - /** - * rcu_dereference_raw - fetch an RCU-protected pointer + * rcu_assign_pointer() - assign to RCU-protected pointer + * @p: pointer to assign to + * @v: value to assign (publish) * - * 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_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. + * 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 * (pretty much all of them other than x86), and also prevents @@ -476,14 +580,17 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) * call documents which pointers will be dereferenced by RCU read-side * code. */ - #define rcu_assign_pointer(p, v) \ - ({ \ - if (!__builtin_constant_p(v) || \ - ((v) != NULL)) \ - smp_wmb(); \ - (p) = (v); \ - }) + __rcu_assign_pointer((p), (v), __rcu) + +/** + * RCU_INIT_POINTER() - initialize an RCU protected pointer + * + * Initialize an RCU-protected pointer in such a way to avoid RCU-lockdep + * splats. + */ +#define RCU_INIT_POINTER(p, v) \ + p = (typeof(*v) __force __rcu *)(v) /* Infrastructure to implement the synchronize_() primitives. */ @@ -495,7 +602,7 @@ struct rcu_synchronize { extern void wakeme_after_rcu(struct rcu_head *head); /** - * call_rcu - Queue an RCU callback for invocation after a grace period. + * 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 * @@ -509,7 +616,7 @@ extern void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *head)); /** - * call_rcu_bh - Queue an RCU for invocation after a quicker grace period. + * 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 update function to be invoked after the grace period * @@ -566,37 +673,4 @@ static inline void debug_rcu_head_unqueue(struct rcu_head *head) } #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ -#ifndef CONFIG_PROVE_RCU -#define __do_rcu_dereference_check(c) do { } while (0) -#endif /* #ifdef CONFIG_PROVE_RCU */ - -#define __rcu_dereference_index_check(p, c) \ - ({ \ - typeof(p) _________p1 = ACCESS_ONCE(p); \ - __do_rcu_dereference_check(c); \ - smp_read_barrier_depends(); \ - (_________p1); \ - }) - -/** - * 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)) - #endif /* __LINUX_RCUPDATE_H */ diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 4d5d2f546db..6f456a720ff 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -108,12 +108,31 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp) #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ /** - * srcu_dereference - fetch SRCU-protected pointer with checking + * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing + * @p: the pointer to fetch and protect for later dereferencing + * @sp: pointer to the srcu_struct, which is used to check that we + * really are in an SRCU read-side critical section. + * @c: condition to check for update-side use * - * Makes rcu_dereference_check() do the dirty work. + * If PROVE_RCU is enabled, invoking this outside of an RCU read-side + * critical section will result in an RCU-lockdep splat, unless @c evaluates + * to 1. The @c argument will normally be a logical expression containing + * lockdep_is_held() calls. */ -#define srcu_dereference(p, sp) \ - rcu_dereference_check(p, srcu_read_lock_held(sp)) +#define srcu_dereference_check(p, sp, c) \ + __rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu) + +/** + * srcu_dereference - fetch SRCU-protected pointer for later dereferencing + * @p: the pointer to fetch and protect for later dereferencing + * @sp: pointer to the srcu_struct, which is used to check that we + * really are in an SRCU read-side critical section. + * + * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU + * is enabled, invoking this outside of an RCU read-side critical + * section will result in an RCU-lockdep splat. + */ +#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) /** * srcu_read_lock - register a new reader for an SRCU-protected structure. |