Index: fusl/src/aio/aio.c |
diff --git a/fusl/src/aio/aio.c b/fusl/src/aio/aio.c |
new file mode 100644 |
index 0000000000000000000000000000000000000000..aafd8e8cb77862aad069a1d5dd7ccefc8db42a2b |
--- /dev/null |
+++ b/fusl/src/aio/aio.c |
@@ -0,0 +1,379 @@ |
+#include <aio.h> |
+#include <pthread.h> |
+#include <semaphore.h> |
+#include <limits.h> |
+#include <errno.h> |
+#include <unistd.h> |
+#include <stdlib.h> |
+#include "syscall.h" |
+#include "atomic.h" |
+#include "libc.h" |
+#include "pthread_impl.h" |
+ |
+/* The following is a threads-based implementation of AIO with minimal |
+ * dependence on implementation details. Most synchronization is |
+ * performed with pthread primitives, but atomics and futex operations |
+ * are used for notification in a couple places where the pthread |
+ * primitives would be inefficient or impractical. |
+ * |
+ * For each fd with outstanding aio operations, an aio_queue structure |
+ * is maintained. These are reference-counted and destroyed by the last |
+ * aio worker thread to exit. Accessing any member of the aio_queue |
+ * structure requires a lock on the aio_queue. Adding and removing aio |
+ * queues themselves requires a write lock on the global map object, |
+ * a 4-level table mapping file descriptor numbers to aio queues. A |
+ * read lock on the map is used to obtain locks on existing queues by |
+ * excluding destruction of the queue by a different thread while it is |
+ * being locked. |
+ * |
+ * Each aio queue has a list of active threads/operations. Presently there |
+ * is a one to one relationship between threads and operations. The only |
+ * members of the aio_thread structure which are accessed by other threads |
+ * are the linked list pointers, op (which is immutable), running (which |
+ * is updated atomically), and err (which is synchronized via running), |
+ * so no locking is necessary. Most of the other other members are used |
+ * for sharing data between the main flow of execution and cancellation |
+ * cleanup handler. |
+ * |
+ * Taking any aio locks requires having all signals blocked. This is |
+ * necessary because aio_cancel is needed by close, and close is required |
+ * to be async-signal safe. All aio worker threads run with all signals |
+ * blocked permanently. |
+ */ |
+ |
+struct aio_args { |
+ struct aiocb *cb; |
+ int op; |
+ int err; |
+ sem_t sem; |
+}; |
+ |
+struct aio_thread { |
+ pthread_t td; |
+ struct aiocb *cb; |
+ struct aio_thread *next, *prev; |
+ struct aio_queue *q; |
+ volatile int running; |
+ int err, op; |
+ ssize_t ret; |
+}; |
+ |
+struct aio_queue { |
+ int fd, seekable, append, ref, init; |
+ pthread_mutex_t lock; |
+ pthread_cond_t cond; |
+ struct aio_thread *head; |
+}; |
+ |
+static pthread_rwlock_t maplock = PTHREAD_RWLOCK_INITIALIZER; |
+static struct aio_queue *****map; |
+static volatile int aio_fd_cnt; |
+volatile int __aio_fut; |
+ |
+static struct aio_queue *__aio_get_queue(int fd, int need) |
+{ |
+ if (fd < 0) return 0; |
+ int a=fd>>24; |
+ unsigned char b=fd>>16, c=fd>>8, d=fd; |
+ struct aio_queue *q = 0; |
+ pthread_rwlock_rdlock(&maplock); |
+ if ((!map || !map[a] || !map[a][b] || !map[a][b][c] || !(q=map[a][b][c][d])) && need) { |
+ pthread_rwlock_unlock(&maplock); |
+ pthread_rwlock_wrlock(&maplock); |
+ if (!map) map = calloc(sizeof *map, (-1U/2+1)>>24); |
+ if (!map) goto out; |
+ if (!map[a]) map[a] = calloc(sizeof **map, 256); |
+ if (!map[a]) goto out; |
+ if (!map[a][b]) map[a][b] = calloc(sizeof ***map, 256); |
+ if (!map[a][b]) goto out; |
+ if (!map[a][b][c]) map[a][b][c] = calloc(sizeof ****map, 256); |
+ if (!map[a][b][c]) goto out; |
+ if (!(q = map[a][b][c][d])) { |
+ map[a][b][c][d] = q = calloc(sizeof *****map, 1); |
+ if (q) { |
+ q->fd = fd; |
+ pthread_mutex_init(&q->lock, 0); |
+ pthread_cond_init(&q->cond, 0); |
+ a_inc(&aio_fd_cnt); |
+ } |
+ } |
+ } |
+ if (q) pthread_mutex_lock(&q->lock); |
+out: |
+ pthread_rwlock_unlock(&maplock); |
+ return q; |
+} |
+ |
+static void __aio_unref_queue(struct aio_queue *q) |
+{ |
+ if (q->ref > 1) { |
+ q->ref--; |
+ pthread_mutex_unlock(&q->lock); |
+ return; |
+ } |
+ |
+ /* This is potentially the last reference, but a new reference |
+ * may arrive since we cannot free the queue object without first |
+ * taking the maplock, which requires releasing the queue lock. */ |
+ pthread_mutex_unlock(&q->lock); |
+ pthread_rwlock_wrlock(&maplock); |
+ pthread_mutex_lock(&q->lock); |
+ if (q->ref == 1) { |
+ int fd=q->fd; |
+ int a=fd>>24; |
+ unsigned char b=fd>>16, c=fd>>8, d=fd; |
+ map[a][b][c][d] = 0; |
+ a_dec(&aio_fd_cnt); |
+ pthread_rwlock_unlock(&maplock); |
+ pthread_mutex_unlock(&q->lock); |
+ free(q); |
+ } else { |
+ q->ref--; |
+ pthread_rwlock_unlock(&maplock); |
+ pthread_mutex_unlock(&q->lock); |
+ } |
+} |
+ |
+static void cleanup(void *ctx) |
+{ |
+ struct aio_thread *at = ctx; |
+ struct aio_queue *q = at->q; |
+ struct aiocb *cb = at->cb; |
+ struct sigevent sev = cb->aio_sigevent; |
+ |
+ /* There are four potential types of waiters we could need to wake: |
+ * 1. Callers of aio_cancel/close. |
+ * 2. Callers of aio_suspend with a single aiocb. |
+ * 3. Callers of aio_suspend with a list. |
+ * 4. AIO worker threads waiting for sequenced operations. |
+ * Types 1-3 are notified via atomics/futexes, mainly for AS-safety |
+ * considerations. Type 4 is notified later via a cond var. */ |
+ |
+ cb->__ret = at->ret; |
+ if (a_swap(&at->running, 0) < 0) |
+ __wake(&at->running, -1, 1); |
+ if (a_swap(&cb->__err, at->err) != EINPROGRESS) |
+ __wake(&cb->__err, -1, 1); |
+ if (a_swap(&__aio_fut, 0)) |
+ __wake(&__aio_fut, -1, 1); |
+ |
+ pthread_mutex_lock(&q->lock); |
+ |
+ if (at->next) at->next->prev = at->prev; |
+ if (at->prev) at->prev->next = at->next; |
+ else q->head = at->next; |
+ |
+ /* Signal aio worker threads waiting for sequenced operations. */ |
+ pthread_cond_broadcast(&q->cond); |
+ |
+ __aio_unref_queue(q); |
+ |
+ if (sev.sigev_notify == SIGEV_SIGNAL) { |
+ siginfo_t si = { |
+ .si_signo = sev.sigev_signo, |
+ .si_value = sev.sigev_value, |
+ .si_code = SI_ASYNCIO, |
+ .si_pid = getpid(), |
+ .si_uid = getuid() |
+ }; |
+ __syscall(SYS_rt_sigqueueinfo, si.si_pid, si.si_signo, &si); |
+ } |
+ if (sev.sigev_notify == SIGEV_THREAD) { |
+ a_store(&__pthread_self()->cancel, 0); |
+ sev.sigev_notify_function(sev.sigev_value); |
+ } |
+} |
+ |
+static void *io_thread_func(void *ctx) |
+{ |
+ struct aio_thread at, *p; |
+ |
+ struct aio_args *args = ctx; |
+ struct aiocb *cb = args->cb; |
+ int fd = cb->aio_fildes; |
+ int op = args->op; |
+ void *buf = (void *)cb->aio_buf; |
+ size_t len = cb->aio_nbytes; |
+ off_t off = cb->aio_offset; |
+ |
+ struct aio_queue *q = __aio_get_queue(fd, 1); |
+ ssize_t ret; |
+ |
+ args->err = q ? 0 : EAGAIN; |
+ sem_post(&args->sem); |
+ if (!q) return 0; |
+ |
+ at.op = op; |
+ at.running = 1; |
+ at.ret = -1; |
+ at.err = ECANCELED; |
+ at.q = q; |
+ at.td = __pthread_self(); |
+ at.cb = cb; |
+ at.prev = 0; |
+ if ((at.next = q->head)) at.next->prev = &at; |
+ q->head = &at; |
+ q->ref++; |
+ |
+ if (!q->init) { |
+ int seekable = lseek(fd, 0, SEEK_CUR) >= 0; |
+ q->seekable = seekable; |
+ q->append = !seekable || (fcntl(fd, F_GETFL) & O_APPEND); |
+ q->init = 1; |
+ } |
+ |
+ pthread_cleanup_push(cleanup, &at); |
+ |
+ /* Wait for sequenced operations. */ |
+ if (op!=LIO_READ && (op!=LIO_WRITE || q->append)) { |
+ for (;;) { |
+ for (p=at.next; p && p->op!=LIO_WRITE; p=p->next); |
+ if (!p) break; |
+ pthread_cond_wait(&q->cond, &q->lock); |
+ } |
+ } |
+ |
+ pthread_mutex_unlock(&q->lock); |
+ |
+ switch (op) { |
+ case LIO_WRITE: |
+ ret = q->append ? write(fd, buf, len) : pwrite(fd, buf, len, off); |
+ break; |
+ case LIO_READ: |
+ ret = !q->seekable ? read(fd, buf, len) : pread(fd, buf, len, off); |
+ break; |
+ case O_SYNC: |
+ ret = fsync(fd); |
+ break; |
+ case O_DSYNC: |
+ ret = fdatasync(fd); |
+ break; |
+ } |
+ at.ret = ret; |
+ at.err = ret<0 ? errno : 0; |
+ |
+ pthread_cleanup_pop(1); |
+ |
+ return 0; |
+} |
+ |
+static int submit(struct aiocb *cb, int op) |
+{ |
+ int ret = 0; |
+ pthread_attr_t a; |
+ sigset_t allmask, origmask; |
+ pthread_t td; |
+ struct aio_args args = { .cb = cb, .op = op }; |
+ sem_init(&args.sem, 0, 0); |
+ |
+ if (cb->aio_sigevent.sigev_notify == SIGEV_THREAD) { |
+ if (cb->aio_sigevent.sigev_notify_attributes) |
+ a = *cb->aio_sigevent.sigev_notify_attributes; |
+ else |
+ pthread_attr_init(&a); |
+ } else { |
+ pthread_attr_init(&a); |
+ pthread_attr_setstacksize(&a, PTHREAD_STACK_MIN); |
+ pthread_attr_setguardsize(&a, 0); |
+ } |
+ pthread_attr_setdetachstate(&a, PTHREAD_CREATE_DETACHED); |
+ sigfillset(&allmask); |
+ pthread_sigmask(SIG_BLOCK, &allmask, &origmask); |
+ cb->__err = EINPROGRESS; |
+ if (pthread_create(&td, &a, io_thread_func, &args)) { |
+ errno = EAGAIN; |
+ ret = -1; |
+ } |
+ pthread_sigmask(SIG_SETMASK, &origmask, 0); |
+ |
+ if (!ret) { |
+ while (sem_wait(&args.sem)); |
+ if (args.err) { |
+ errno = args.err; |
+ ret = -1; |
+ } |
+ } |
+ |
+ return ret; |
+} |
+ |
+int aio_read(struct aiocb *cb) |
+{ |
+ return submit(cb, LIO_READ); |
+} |
+ |
+int aio_write(struct aiocb *cb) |
+{ |
+ return submit(cb, LIO_WRITE); |
+} |
+ |
+int aio_fsync(int op, struct aiocb *cb) |
+{ |
+ if (op != O_SYNC && op != O_DSYNC) { |
+ errno = EINVAL; |
+ return -1; |
+ } |
+ return submit(cb, op); |
+} |
+ |
+ssize_t aio_return(struct aiocb *cb) |
+{ |
+ return cb->__ret; |
+} |
+ |
+int aio_error(const struct aiocb *cb) |
+{ |
+ a_barrier(); |
+ return cb->__err & 0x7fffffff; |
+} |
+ |
+int aio_cancel(int fd, struct aiocb *cb) |
+{ |
+ sigset_t allmask, origmask; |
+ int ret = AIO_ALLDONE; |
+ struct aio_thread *p; |
+ struct aio_queue *q; |
+ |
+ /* Unspecified behavior case. Report an error. */ |
+ if (cb && fd != cb->aio_fildes) { |
+ errno = EINVAL; |
+ return -1; |
+ } |
+ |
+ sigfillset(&allmask); |
+ pthread_sigmask(SIG_BLOCK, &allmask, &origmask); |
+ |
+ if (!(q = __aio_get_queue(fd, 0))) { |
+ if (fcntl(fd, F_GETFD) < 0) ret = -1; |
+ goto done; |
+ } |
+ |
+ for (p = q->head; p; p = p->next) { |
+ if (cb && cb != p->cb) continue; |
+ /* Transition target from running to running-with-waiters */ |
+ if (a_cas(&p->running, 1, -1)) { |
+ pthread_cancel(p->td); |
+ __wait(&p->running, 0, -1, 1); |
+ if (p->err == ECANCELED) ret = AIO_CANCELED; |
+ } |
+ } |
+ |
+ pthread_mutex_unlock(&q->lock); |
+done: |
+ pthread_sigmask(SIG_SETMASK, &origmask, 0); |
+ return ret; |
+} |
+ |
+int __aio_close(int fd) |
+{ |
+ a_barrier(); |
+ if (aio_fd_cnt) aio_cancel(fd, 0); |
+ return fd; |
+} |
+ |
+LFS64(aio_cancel); |
+LFS64(aio_error); |
+LFS64(aio_fsync); |
+LFS64(aio_read); |
+LFS64(aio_write); |
+LFS64(aio_return); |