Re: [PATCH 3/6] 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.

[Paul Durrant <xadimgnik@xxxxxxxxx>]

On 20/07/2021 14:29, Martin Harvey wrote:
> Signed-off-by: Martin Harvey <martin.harvey@xxxxxxxxxx>
> ---
>   src/xenvif/frontend.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/src/xenvif/frontend.c b/src/xenvif/frontend.c
> index 5940e16..c27b2cd 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             TimeoutDelta = 120000;
NIT: I don't think you really need 'Delta' in the name, just 'Timeout' 
would suffice (and I think it would be more consistent with other code).
>   
>       Trace("%s: ====> %s\n",
>             __FrontendGetBackendPath(Frontend),
> @@ -1369,7 +1370,7 @@ FrontendWaitForBackendXenbusStateChange(
>   
>       Timeout.QuadPart = 0;
>   
> -    while (*State == Old && TimeDelta < 120000) {
> +    while (*State == Old && TimeDelta < TimeoutDelta) {
>           PCHAR           Buffer;
>           LARGE_INTEGER   Now;
>   
> @@ -1417,6 +1418,10 @@ FrontendWaitForBackendXenbusStateChange(
>           TimeDelta = (Now.QuadPart - Start.QuadPart) / 10000ull;
>       }
>   
> +    if (TimeDelta >= TimeoutDelta) {
> +        Error("%s timed out.\n", __FrontendGetBackendPath(Frontend));
> +    }
No need for braces on single-line ifs and no full stop needed in the log 
message. Since it's not in context and I can't remember... does the path 
include the actual 'state' key name? It's a lack of change in that 
particular key we're triggering on here.
  Paul

> +
>       if (Watch != NULL)
>           (VOID) XENBUS_STORE(WatchRemove,
>                               &Frontend->StoreInterface,