--- /dev/null
+#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;
+ int running, 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. */
+
+ a_store(&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);
+++ /dev/null
-#include <aio.h>
-#include <fcntl.h>
-#include <errno.h>
-#include <unistd.h>
-#include "pthread_impl.h"
-#include "libc.h"
-
-static void dummy(void)
-{
-}
-
-weak_alias(dummy, __aio_wake);
-
-static void notify_signal(struct sigevent *sev)
-{
- 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);
-}
-
-static void *io_thread(void *p)
-{
- struct aiocb *cb = p;
- int fd = cb->aio_fildes;
- void *buf = (void *)cb->aio_buf;
- size_t len = cb->aio_nbytes;
- off_t off = cb->aio_offset;
- int op = cb->aio_lio_opcode;
- struct sigevent sev = cb->aio_sigevent;
- ssize_t ret;
-
- if (op == LIO_WRITE) {
- if ( (fcntl(fd, F_GETFL) & O_APPEND)
- ||((ret = pwrite(fd, buf, len, off))<0 && errno==ESPIPE) )
- ret = write(fd, buf, len);
- } else if (op == LIO_READ) {
- if ( (ret = pread(fd, buf, len, off))<0 && errno==ESPIPE )
- ret = read(fd, buf, len);
- } else {
- ret = 0;
- }
- cb->__ret = ret;
-
- if (ret < 0) a_store(&cb->__err, errno);
- else a_store(&cb->__err, 0);
-
- __aio_wake();
-
- switch (sev.sigev_notify) {
- case SIGEV_SIGNAL:
- notify_signal(&sev);
- break;
- case SIGEV_THREAD:
- sev.sigev_notify_function(sev.sigev_value);
- break;
- }
-
- return 0;
-}
-
-static int new_req(struct aiocb *cb)
-{
- int ret = 0;
- pthread_attr_t a;
- sigset_t set;
- pthread_t td;
-
- 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, PAGE_SIZE);
- pthread_attr_setguardsize(&a, 0);
- }
- pthread_attr_setdetachstate(&a, PTHREAD_CREATE_DETACHED);
- sigfillset(&set);
- pthread_sigmask(SIG_BLOCK, &set, &set);
- cb->__err = EINPROGRESS;
- if (pthread_create(&td, &a, io_thread, cb)) {
- errno = EAGAIN;
- ret = -1;
- }
- pthread_sigmask(SIG_SETMASK, &set, 0);
- cb->__td = td;
-
- return ret;
-}
-
-int aio_read(struct aiocb *cb)
-{
- cb->aio_lio_opcode = LIO_READ;
- return new_req(cb);
-}
-
-int aio_write(struct aiocb *cb)
-{
- cb->aio_lio_opcode = LIO_WRITE;
- return new_req(cb);
-}
-
-LFS64(aio_read);
-LFS64(aio_write);
#include <aio.h>
#include <errno.h>
-#include "pthread_impl.h"
+#include <time.h>
+#include "atomic.h"
#include "libc.h"
+#include "pthread_impl.h"
-/* Due to the requirement that aio_suspend be async-signal-safe, we cannot
- * use any locks, wait queues, etc. that would make it more efficient. The
- * only obviously-correct algorithm is to generate a wakeup every time any
- * aio operation finishes and have aio_suspend re-evaluate the completion
- * status of each aiocb it was waiting on. */
-
-static volatile int seq;
-
-void __aio_wake(void)
-{
- a_inc(&seq);
- __wake(&seq, -1, 1);
-}
+extern volatile int __aio_fut;
int aio_suspend(const struct aiocb *const cbs[], int cnt, const struct timespec *ts)
{
- int i, last, first=1, ret=0;
+ int i, tid = 0, ret, expect = 0;
struct timespec at;
+ volatile int dummy_fut, *pfut;
+ int nzcnt = 0;
+ const struct aiocb *cb = 0;
if (cnt<0) {
errno = EINVAL;
return -1;
}
- for (;;) {
- last = seq;
+ for (i=0; i<cnt; i++) if (cbs[i]) {
+ if (aio_error(cbs[i]) != EINPROGRESS) return 0;
+ nzcnt++;
+ cb = cbs[i];
+ }
- for (i=0; i<cnt; i++) {
- if (cbs[i] && cbs[i]->__err != EINPROGRESS)
- return 0;
+ if (ts) {
+ clock_gettime(CLOCK_MONOTONIC, &at);
+ at.tv_sec += ts->tv_sec;
+ if ((at.tv_nsec += ts->tv_nsec) >= 1000000000) {
+ at.tv_nsec -= 1000000000;
+ at.tv_sec++;
}
+ }
- if (first && ts) {
- clock_gettime(CLOCK_MONOTONIC, &at);
- at.tv_sec += ts->tv_sec;
- if ((at.tv_nsec += ts->tv_nsec) >= 1000000000) {
- at.tv_nsec -= 1000000000;
- at.tv_sec++;
- }
- first = 0;
- }
+ for (;;) {
+ for (i=0; i<cnt; i++)
+ if (cbs[i] && aio_error(cbs[i]) != EINPROGRESS)
+ return 0;
- ret = __timedwait(&seq, last, CLOCK_MONOTONIC,
- ts ? &at : 0, 0, 0, 1);
+ switch (nzcnt) {
+ case 0:
+ pfut = &dummy_fut;
+ break;
+ case 1:
+ pfut = (void *)&cb->__err;
+ expect = EINPROGRESS | 0x80000000;
+ a_cas(pfut, EINPROGRESS, expect);
+ break;
+ default:
+ pfut = &__aio_fut;
+ if (!tid) tid = __pthread_self()->tid;
+ expect = a_cas(pfut, 0, tid);
+ if (!expect) expect = tid;
+ /* Need to recheck the predicate before waiting. */
+ for (i=0; i<cnt; i++)
+ if (cbs[i] && aio_error(cbs[i]) != EINPROGRESS)
+ return 0;
+ break;
+ }
- if (ret == ETIMEDOUT) ret = EAGAIN;
+ ret = __timedwait(pfut, expect, CLOCK_MONOTONIC, ts?&at:0, 0, 0, 1);
if (ret) {
- errno = ret;
+ errno = ret==ETIMEDOUT ? EAGAIN : ret;
return -1;
}
}
projects / oweals / musl.git / commitdiff