Il 09/02/2013 17:44, Stefan Hajnoczi ha scritto:
> bdrv_co_io_em(), bdrv_co_flush(), and bdrv_co_discard() yield the
> coroutine when waiting for aio to complete. They do not check that the
> request has actually finished.
>
> In simple cases this works, but it returns early when we get spurious
> wake-ups due to qemu_coroutine_enter() being called from other sources.
> One such example is block-migration.c:process_incoming_migration().
>
> This patch fixes a segfault on incoming block migration.
>
> Reported-by: David Pravec <david.pra...@nethost.cz>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
I would prefer to have ret initialized to -EINPROGRESS, but since we're
close to release it's easier this way.
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> This patch is partially fixes block migration. There is another issue that
> causes block migration to fail with "Unknown flags" at 99%.
>
> block.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/block.c b/block.c
> index 50dab8e..f2f3b80 100644
> --- a/block.c
> +++ b/block.c
> @@ -3961,6 +3961,7 @@ void qemu_aio_release(void *p)
> typedef struct CoroutineIOCompletion {
> Coroutine *coroutine;
> int ret;
> + bool done;
> } CoroutineIOCompletion;
>
> static void bdrv_co_io_em_complete(void *opaque, int ret)
> @@ -3968,6 +3969,7 @@ static void bdrv_co_io_em_complete(void *opaque, int
> ret)
> CoroutineIOCompletion *co = opaque;
>
> co->ret = ret;
> + co->done = true;
> qemu_coroutine_enter(co->coroutine, NULL);
> }
>
> @@ -3992,7 +3994,9 @@ static int coroutine_fn bdrv_co_io_em(BlockDriverState
> *bs, int64_t sector_num,
> if (!acb) {
> return -EIO;
> }
> - qemu_coroutine_yield();
> + while (!co.done) {
> + qemu_coroutine_yield();
> + }
>
> return co.ret;
> }
> @@ -4051,7 +4055,9 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
> if (acb == NULL) {
> ret = -EIO;
> } else {
> - qemu_coroutine_yield();
> + while (!co.done) {
> + qemu_coroutine_yield();
> + }
> ret = co.ret;
> }
> } else {
> @@ -4161,7 +4167,9 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs,
> int64_t sector_num,
> if (acb == NULL) {
> return -EIO;
> } else {
> - qemu_coroutine_yield();
> + while (!co.done) {
> + qemu_coroutine_yield();
> + }
> return co.ret;
> }
> } else {
>
