Re: [RFC PATCH 3/3] block: Assert we're running in the right thread

[Stefan Reiter <s.reiter@proxmox.com>]

On 5/12/20 4:43 PM, Kevin Wolf wrote:
> tracked_request_begin() is called for most I/O operations, so it's a
> good place to assert that we're indeed running in the home thread of the
> node's AioContext.
> 

Is this patch supposed to be always correct or only together with nr. 2?

I changed our code to call bdrv_flush_all from the main AIO context and 
it certainly works just fine (even without this series, so I suppose 
that would be the 'correct' way to fix it you mention on the cover), 
though of course it trips this assert without patch 2.

> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block/io.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/block/io.c b/block/io.c
> index 7808e8bdc0..924bf5ba46 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -695,14 +695,17 @@ static void tracked_request_begin(BdrvTrackedRequest *req,
>                                     uint64_t bytes,
>                                     enum BdrvTrackedRequestType type)
>   {
> +    Coroutine *self = qemu_coroutine_self();
> +
>       assert(bytes <= INT64_MAX && offset <= INT64_MAX - bytes);
> +    assert(bs->aio_context == qemu_coroutine_get_aio_context(self));
>   
>       *req = (BdrvTrackedRequest){
>           .bs = bs,
>           .offset         = offset,
>           .bytes          = bytes,
>           .type           = type,
> -        .co             = qemu_coroutine_self(),
> +        .co             = self,
>           .serialising    = false,
>           .overlap_offset = offset,
>           .overlap_bytes  = bytes,
>