diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/qemu/atomic.h | 61 | ||||
| -rw-r--r-- | include/qemu/queue.h | 13 | ||||
| -rw-r--r-- | include/qemu/rcu.h | 112 | ||||
| -rw-r--r-- | include/qemu/thread.h | 3 |
4 files changed, 186 insertions, 3 deletions
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index 93c2ae2f37..98e05ca875 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -129,6 +129,67 @@ #define atomic_set(ptr, i) ((*(__typeof__(*ptr) volatile*) (ptr)) = (i)) #endif +/** + * atomic_rcu_read - reads a RCU-protected pointer to a local variable + * into a RCU read-side critical section. The pointer can later be safely + * dereferenced within the critical section. + * + * This ensures that the pointer copy is invariant thorough the whole critical + * section. + * + * Inserts memory barriers on architectures that require them (currently only + * Alpha) and documents which pointers are protected by RCU. + * + * Unless the __ATOMIC_CONSUME memory order is available, atomic_rcu_read also + * includes a compiler barrier to ensure that value-speculative optimizations + * (e.g. VSS: Value Speculation Scheduling) does not perform the data read + * before the pointer read by speculating the value of the pointer. On new + * enough compilers, atomic_load takes care of such concern about + * dependency-breaking optimizations. + * + * Should match atomic_rcu_set(), atomic_xchg(), atomic_cmpxchg(). + */ +#ifndef atomic_rcu_read +#ifdef __ATOMIC_CONSUME +#define atomic_rcu_read(ptr) ({ \ + typeof(*ptr) _val; \ + __atomic_load(ptr, &_val, __ATOMIC_CONSUME); \ + _val; \ +}) +#else +#define atomic_rcu_read(ptr) ({ \ + typeof(*ptr) _val = atomic_read(ptr); \ + smp_read_barrier_depends(); \ + _val; \ +}) +#endif +#endif + +/** + * atomic_rcu_set - assigns (publicizes) a pointer to a new data structure + * meant to be read by RCU read-side critical sections. + * + * Documents which pointers will be dereferenced by RCU read-side critical + * sections and adds the required memory barriers on architectures requiring + * them. It also makes sure the compiler does not reorder code initializing the + * data structure before its publication. + * + * Should match atomic_rcu_read(). + */ +#ifndef atomic_rcu_set +#ifdef __ATOMIC_RELEASE +#define atomic_rcu_set(ptr, i) do { \ + typeof(*ptr) _val = (i); \ + __atomic_store(ptr, &_val, __ATOMIC_RELEASE); \ +} while(0) +#else +#define atomic_rcu_set(ptr, i) do { \ + smp_wmb(); \ + atomic_set(ptr, i); \ +} while (0) +#endif +#endif + /* These have the same semantics as Java volatile variables. * See http://gee.cs.oswego.edu/dl/jmm/cookbook.html: * "1. Issue a StoreStore barrier (wmb) before each volatile store." diff --git a/include/qemu/queue.h b/include/qemu/queue.h index a98eb3ad79..c602797652 100644 --- a/include/qemu/queue.h +++ b/include/qemu/queue.h @@ -104,6 +104,19 @@ struct { \ (head)->lh_first = NULL; \ } while (/*CONSTCOND*/0) +#define QLIST_SWAP(dstlist, srclist, field) do { \ + void *tmplist; \ + tmplist = (srclist)->lh_first; \ + (srclist)->lh_first = (dstlist)->lh_first; \ + if ((srclist)->lh_first != NULL) { \ + (srclist)->lh_first->field.le_prev = &(srclist)->lh_first; \ + } \ + (dstlist)->lh_first = tmplist; \ + if ((dstlist)->lh_first != NULL) { \ + (dstlist)->lh_first->field.le_prev = &(dstlist)->lh_first; \ + } \ +} while (/*CONSTCOND*/0) + #define QLIST_INSERT_AFTER(listelm, elm, field) do { \ if (((elm)->field.le_next = (listelm)->field.le_next) != NULL) \ (listelm)->field.le_next->field.le_prev = \ diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h new file mode 100644 index 0000000000..cfef36e25a --- /dev/null +++ b/include/qemu/rcu.h @@ -0,0 +1,112 @@ +#ifndef QEMU_RCU_H +#define QEMU_RCU_H + +/* + * urcu-mb.h + * + * Userspace RCU header with explicit memory barrier. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library 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 + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * IBM's contributions to this file may be relicensed under LGPLv2 or later. + */ + +#include <stdlib.h> +#include <assert.h> +#include <limits.h> +#include <unistd.h> +#include <stdint.h> +#include <stdbool.h> +#include <glib.h> + +#include "qemu/compiler.h" +#include "qemu/thread.h" +#include "qemu/queue.h" +#include "qemu/atomic.h" + +#ifdef __cplusplus +extern "C" { +#endif + +/* + * Important ! + * + * Each thread containing read-side critical sections must be registered + * with rcu_register_thread() before calling rcu_read_lock(). + * rcu_unregister_thread() should be called before the thread exits. + */ + +#ifdef DEBUG_RCU +#define rcu_assert(args...) assert(args) +#else +#define rcu_assert(args...) +#endif + +/* + * Global quiescent period counter with low-order bits unused. + * Using a int rather than a char to eliminate false register dependencies + * causing stalls on some architectures. + */ +extern unsigned long rcu_gp_ctr; + +extern QemuEvent rcu_gp_event; + +struct rcu_reader_data { + /* Data used by both reader and synchronize_rcu() */ + unsigned long ctr; + bool waiting; + + /* Data used for registry, protected by rcu_gp_lock */ + QLIST_ENTRY(rcu_reader_data) node; +}; + +extern __thread struct rcu_reader_data rcu_reader; + +static inline void rcu_read_lock(void) +{ + struct rcu_reader_data *p_rcu_reader = &rcu_reader; + + unsigned ctr = atomic_read(&rcu_gp_ctr); + atomic_xchg(&p_rcu_reader->ctr, ctr); + if (atomic_read(&p_rcu_reader->waiting)) { + atomic_set(&p_rcu_reader->waiting, false); + qemu_event_set(&rcu_gp_event); + } +} + +static inline void rcu_read_unlock(void) +{ + struct rcu_reader_data *p_rcu_reader = &rcu_reader; + + atomic_xchg(&p_rcu_reader->ctr, 0); + if (atomic_read(&p_rcu_reader->waiting)) { + atomic_set(&p_rcu_reader->waiting, false); + qemu_event_set(&rcu_gp_event); + } +} + +extern void synchronize_rcu(void); + +/* + * Reader thread registration. + */ +extern void rcu_register_thread(void); +extern void rcu_unregister_thread(void); + +#ifdef __cplusplus +} +#endif + +#endif /* QEMU_RCU_H */ diff --git a/include/qemu/thread.h b/include/qemu/thread.h index e89fdc9785..5114ec8e79 100644 --- a/include/qemu/thread.h +++ b/include/qemu/thread.h @@ -25,9 +25,6 @@ void qemu_mutex_lock(QemuMutex *mutex); int qemu_mutex_trylock(QemuMutex *mutex); void qemu_mutex_unlock(QemuMutex *mutex); -#define rcu_read_lock() do { } while (0) -#define rcu_read_unlock() do { } while (0) - void qemu_cond_init(QemuCond *cond); void qemu_cond_destroy(QemuCond *cond); |