* THE SOFTWARE.
*/
+#include "qemu/osdep.h"
+#include "qapi/error.h"
#include "qemu-common.h"
#include "block/aio.h"
#include "block/thread-pool.h"
#include "qemu/main-loop.h"
+#include "qemu/atomic.h"
/***********************************************************/
/* bottom halves (can be seen as timers which expire ASAP) */
QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
{
QEMUBH *bh;
- bh = g_malloc0(sizeof(QEMUBH));
- bh->ctx = ctx;
- bh->cb = cb;
- bh->opaque = opaque;
+ bh = g_new(QEMUBH, 1);
+ *bh = (QEMUBH){
+ .ctx = ctx,
+ .cb = cb,
+ .opaque = opaque,
+ };
qemu_mutex_lock(&ctx->bh_lock);
bh->next = ctx->first_bh;
/* Make sure that the members are ready before putting bh into list */
return bh;
}
+void aio_bh_call(QEMUBH *bh)
+{
+ bh->cb(bh->opaque);
+}
+
/* Multiple occurrences of aio_bh_poll cannot be called concurrently */
int aio_bh_poll(AioContext *ctx)
{
/* Make sure that fetching bh happens before accessing its members */
smp_read_barrier_depends();
next = bh->next;
- if (!bh->deleted && bh->scheduled) {
- bh->scheduled = 0;
- /* Paired with write barrier in bh schedule to ensure reading for
- * idle & callbacks coming after bh's scheduling.
- */
- smp_rmb();
- if (!bh->idle)
+ /* The atomic_xchg is paired with the one in qemu_bh_schedule. The
+ * implicit memory barrier ensures that the callback sees all writes
+ * done by the scheduling thread. It also ensures that the scheduling
+ * thread sees the zero before bh->cb has run, and thus will call
+ * aio_notify again if necessary.
+ */
+ if (!bh->deleted && atomic_xchg(&bh->scheduled, 0)) {
+ /* Idle BHs and the notify BH don't count as progress */
+ if (!bh->idle && bh != ctx->notify_dummy_bh) {
ret = 1;
+ }
bh->idle = 0;
- bh->cb(bh->opaque);
+ aio_bh_call(bh);
}
}
void qemu_bh_schedule_idle(QEMUBH *bh)
{
- if (bh->scheduled)
- return;
bh->idle = 1;
/* Make sure that idle & any writes needed by the callback are done
* before the locations are read in the aio_bh_poll.
*/
- smp_wmb();
- bh->scheduled = 1;
+ atomic_mb_set(&bh->scheduled, 1);
}
void qemu_bh_schedule(QEMUBH *bh)
{
- if (bh->scheduled)
- return;
+ AioContext *ctx;
+
+ ctx = bh->ctx;
bh->idle = 0;
- /* Make sure that idle & any writes needed by the callback are done
- * before the locations are read in the aio_bh_poll.
+ /* The memory barrier implicit in atomic_xchg makes sure that:
+ * 1. idle & any writes needed by the callback are done before the
+ * locations are read in the aio_bh_poll.
+ * 2. ctx is loaded before scheduled is set and the callback has a chance
+ * to execute.
*/
- smp_wmb();
- bh->scheduled = 1;
- aio_notify(bh->ctx);
+ if (atomic_xchg(&bh->scheduled, 1) == 0) {
+ aio_notify(ctx);
+ }
}
bh->deleted = 1;
}
-static gboolean
-aio_ctx_prepare(GSource *source, gint *timeout)
+int64_t
+aio_compute_timeout(AioContext *ctx)
{
- AioContext *ctx = (AioContext *) source;
+ int64_t deadline;
+ int timeout = -1;
QEMUBH *bh;
for (bh = ctx->first_bh; bh; bh = bh->next) {
if (bh->idle) {
/* idle bottom halves will be polled at least
* every 10ms */
- *timeout = 10;
+ timeout = 10000000;
} else {
/* non-idle bottom halves will be executed
* immediately */
- *timeout = 0;
- return true;
+ return 0;
}
}
}
- return false;
+ deadline = timerlistgroup_deadline_ns(&ctx->tlg);
+ if (deadline == 0) {
+ return 0;
+ } else {
+ return qemu_soonest_timeout(timeout, deadline);
+ }
+}
+
+static gboolean
+aio_ctx_prepare(GSource *source, gint *timeout)
+{
+ AioContext *ctx = (AioContext *) source;
+
+ atomic_or(&ctx->notify_me, 1);
+
+ /* We assume there is no timeout already supplied */
+ *timeout = qemu_timeout_ns_to_ms(aio_compute_timeout(ctx));
+
+ if (aio_prepare(ctx)) {
+ *timeout = 0;
+ }
+
+ return *timeout == 0;
}
static gboolean
AioContext *ctx = (AioContext *) source;
QEMUBH *bh;
+ atomic_and(&ctx->notify_me, ~1);
+ aio_notify_accept(ctx);
+
for (bh = ctx->first_bh; bh; bh = bh->next) {
if (!bh->deleted && bh->scheduled) {
return true;
}
}
- return aio_pending(ctx);
+ return aio_pending(ctx) || (timerlistgroup_deadline_ns(&ctx->tlg) == 0);
}
static gboolean
AioContext *ctx = (AioContext *) source;
assert(callback == NULL);
- aio_poll(ctx, false);
+ aio_dispatch(ctx);
return true;
}
{
AioContext *ctx = (AioContext *) source;
+ qemu_bh_delete(ctx->notify_dummy_bh);
thread_pool_free(ctx->thread_pool);
- aio_set_event_notifier(ctx, &ctx->notifier, NULL);
+
+ qemu_mutex_lock(&ctx->bh_lock);
+ while (ctx->first_bh) {
+ QEMUBH *next = ctx->first_bh->next;
+
+ /* qemu_bh_delete() must have been called on BHs in this AioContext */
+ assert(ctx->first_bh->deleted);
+
+ g_free(ctx->first_bh);
+ ctx->first_bh = next;
+ }
+ qemu_mutex_unlock(&ctx->bh_lock);
+
+ aio_set_event_notifier(ctx, &ctx->notifier, false, NULL);
event_notifier_cleanup(&ctx->notifier);
+ rfifolock_destroy(&ctx->lock);
qemu_mutex_destroy(&ctx->bh_lock);
- g_array_free(ctx->pollfds, TRUE);
timerlistgroup_deinit(&ctx->tlg);
}
void aio_notify(AioContext *ctx)
{
- event_notifier_set(&ctx->notifier);
+ /* Write e.g. bh->scheduled before reading ctx->notify_me. Pairs
+ * with atomic_or in aio_ctx_prepare or atomic_add in aio_poll.
+ */
+ smp_mb();
+ if (ctx->notify_me) {
+ event_notifier_set(&ctx->notifier);
+ atomic_mb_set(&ctx->notified, true);
+ }
+}
+
+void aio_notify_accept(AioContext *ctx)
+{
+ if (atomic_xchg(&ctx->notified, false)) {
+ event_notifier_test_and_clear(&ctx->notifier);
+ }
}
static void aio_timerlist_notify(void *opaque)
aio_notify(opaque);
}
-AioContext *aio_context_new(void)
+static void aio_rfifolock_cb(void *opaque)
+{
+ AioContext *ctx = opaque;
+
+ /* Kick owner thread in case they are blocked in aio_poll() */
+ qemu_bh_schedule(ctx->notify_dummy_bh);
+}
+
+static void notify_dummy_bh(void *opaque)
+{
+ /* Do nothing, we were invoked just to force the event loop to iterate */
+}
+
+static void event_notifier_dummy_cb(EventNotifier *e)
{
+}
+
+AioContext *aio_context_new(Error **errp)
+{
+ int ret;
AioContext *ctx;
+ Error *local_err = NULL;
+
ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
- ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
+ aio_context_setup(ctx, &local_err);
+ if (local_err) {
+ error_propagate(errp, local_err);
+ goto fail;
+ }
+ ret = event_notifier_init(&ctx->notifier, false);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to initialize event notifier");
+ goto fail;
+ }
+ g_source_set_can_recurse(&ctx->source, true);
+ aio_set_event_notifier(ctx, &ctx->notifier,
+ false,
+ (EventNotifierHandler *)
+ event_notifier_dummy_cb);
ctx->thread_pool = NULL;
qemu_mutex_init(&ctx->bh_lock);
- event_notifier_init(&ctx->notifier, false);
- aio_set_event_notifier(ctx, &ctx->notifier,
- (EventNotifierHandler *)
- event_notifier_test_and_clear);
+ rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
timerlistgroup_init(&ctx->tlg, aio_timerlist_notify, ctx);
+ ctx->notify_dummy_bh = aio_bh_new(ctx, notify_dummy_bh, NULL);
+
return ctx;
+fail:
+ g_source_destroy(&ctx->source);
+ return NULL;
}
void aio_context_ref(AioContext *ctx)
{
g_source_unref(&ctx->source);
}
+
+void aio_context_acquire(AioContext *ctx)
+{
+ rfifolock_lock(&ctx->lock);
+}
+
+void aio_context_release(AioContext *ctx)
+{
+ rfifolock_unlock(&ctx->lock);
+}
projects / qemu.git / blobdiff