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authorStefan Hajnoczi <stefanha@redhat.com>2013-04-11 16:56:50 +0200
committerStefan Hajnoczi <stefanha@redhat.com>2013-08-19 15:45:35 +0200
commit164a101f28a53cd3db60ed874e7c3630e7988ed8 (patch)
tree02aafbb43ca0c97abc2c6b7b7a9ffc70f7d0b2b5 /aio-posix.c
parent35ecde26018207fe723bec6efbd340db6e9c2d53 (diff)
downloadqemu-arm-164a101f28a53cd3db60ed874e7c3630e7988ed8.tar.gz
aio: stop using .io_flush()
Now that aio_poll() users check their termination condition themselves, it is no longer necessary to call .io_flush() handlers. The behavior of aio_poll() changes as follows: 1. .io_flush() is no longer invoked and file descriptors are *always* monitored. Previously returning 0 from .io_flush() would skip this file descriptor. Due to this change it is essential to check that requests are pending before calling qemu_aio_wait(). Failure to do so means we block, for example, waiting for an idle iSCSI socket to become readable when there are no requests. Currently all qemu_aio_wait()/aio_poll() callers check before calling. 2. aio_poll() now returns true if progress was made (BH or fd handlers executed) and false otherwise. Previously it would return true whenever 'busy', which means that .io_flush() returned true. The 'busy' concept no longer exists so just progress is returned. Due to this change we need to update tests/test-aio.c which asserts aio_poll() return values. Note that QEMU doesn't actually rely on these return values so only tests/test-aio.c cares. Note that ctx->notifier, the EventNotifier fd used for aio_notify(), is now handled as a special case. This is a little ugly but maintains aio_poll() semantics, i.e. aio_notify() does not count as 'progress' and aio_poll() avoids blocking when the user has not set any fd handlers yet. Patches after this remove .io_flush() handler code until we can finally drop the io_flush arguments to aio_set_fd_handler() and friends. Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'aio-posix.c')
-rw-r--r--aio-posix.c29
1 files changed, 9 insertions, 20 deletions
diff --git a/aio-posix.c b/aio-posix.c
index b68eccd40c..7d66048b01 100644
--- a/aio-posix.c
+++ b/aio-posix.c
@@ -23,7 +23,6 @@ struct AioHandler
GPollFD pfd;
IOHandler *io_read;
IOHandler *io_write;
- AioFlushHandler *io_flush;
int deleted;
int pollfds_idx;
void *opaque;
@@ -84,7 +83,6 @@ void aio_set_fd_handler(AioContext *ctx,
/* Update handler with latest information */
node->io_read = io_read;
node->io_write = io_write;
- node->io_flush = io_flush;
node->opaque = opaque;
node->pollfds_idx = -1;
@@ -147,7 +145,11 @@ static bool aio_dispatch(AioContext *ctx)
(revents & (G_IO_IN | G_IO_HUP | G_IO_ERR)) &&
node->io_read) {
node->io_read(node->opaque);
- progress = true;
+
+ /* aio_notify() does not count as progress */
+ if (node->opaque != &ctx->notifier) {
+ progress = true;
+ }
}
if (!node->deleted &&
(revents & (G_IO_OUT | G_IO_ERR)) &&
@@ -173,7 +175,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
{
AioHandler *node;
int ret;
- bool busy, progress;
+ bool progress;
progress = false;
@@ -200,20 +202,8 @@ bool aio_poll(AioContext *ctx, bool blocking)
g_array_set_size(ctx->pollfds, 0);
/* fill pollfds */
- busy = false;
QLIST_FOREACH(node, &ctx->aio_handlers, node) {
node->pollfds_idx = -1;
-
- /* If there aren't pending AIO operations, don't invoke callbacks.
- * Otherwise, if there are no AIO requests, qemu_aio_wait() would
- * wait indefinitely.
- */
- if (!node->deleted && node->io_flush) {
- if (node->io_flush(node->opaque) == 0) {
- continue;
- }
- busy = true;
- }
if (!node->deleted && node->pfd.events) {
GPollFD pfd = {
.fd = node->pfd.fd,
@@ -226,8 +216,8 @@ bool aio_poll(AioContext *ctx, bool blocking)
ctx->walking_handlers--;
- /* No AIO operations? Get us out of here */
- if (!busy) {
+ /* early return if we only have the aio_notify() fd */
+ if (ctx->pollfds->len == 1) {
return progress;
}
@@ -250,6 +240,5 @@ bool aio_poll(AioContext *ctx, bool blocking)
}
}
- assert(progress || busy);
- return true;
+ return progress;
}