Re: [PATCH 3/5] Log waits for backend state changes.

[Paul Durrant <xadimgnik@xxxxxxxxx>]

On 28/07/2021 15:02, Martin Harvey wrote:
> In addition to preceding changes to ring disconnects, and
> associated logging, we also add some logging to check
> whether state change notifications are being sent in a timely
> manner between frontend and backend. Also a great assistance
> to customer debugging.
>
> Signed-off-by: Martin Harvey <martin.harvey@xxxxxxxxxx>
Acked-by: Paul Durrant <paul@xxxxxxx>

> ---
>   src/xenvif/frontend.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/src/xenvif/frontend.c b/src/xenvif/frontend.c
> index 5940e16..72f448d 100644
> --- a/src/xenvif/frontend.c
> +++ b/src/xenvif/frontend.c
> @@ -1346,6 +1346,7 @@ FrontendWaitForBackendXenbusStateChange(
>       LARGE_INTEGER               Timeout;
>       XenbusState                 Old = *State;
>       NTSTATUS                    status;
> +    const ULONGLONG             TotalTimeout = 120000;
>   
>       Trace("%s: ====> %s\n",
>             __FrontendGetBackendPath(Frontend),
> @@ -1369,7 +1370,7 @@ FrontendWaitForBackendXenbusStateChange(
>   
>       Timeout.QuadPart = 0;
>   
> -    while (*State == Old && TimeDelta < 120000) {
> +    while (*State == Old && TimeDelta < TotalTimeout) {
>           PCHAR           Buffer;
>           LARGE_INTEGER   Now;
>   
> @@ -1417,6 +1418,9 @@ FrontendWaitForBackendXenbusStateChange(
>           TimeDelta = (Now.QuadPart - Start.QuadPart) / 10000ull;
>       }
>   
> +    if (TimeDelta >= TotalTimeout)
> +        Error("%s timed out waiting for backend state change\n", 
> __FrontendGetBackendPath(Frontend));
> +
>       if (Watch != NULL)
>           (VOID) XENBUS_STORE(WatchRemove,
>                               &Frontend->StoreInterface,