On 05/08/2015 01:23, ronnie sahlberg wrote:
>
> You only get >0 from this call if there are actual bytes available to read.
>
> For context, the problem was that
>
>
> 75 static void nfs_process_read(void *arg)
> 76 {
> 77 NFSClient *client = arg;
> 78 nfs_service(client->context, POLLIN);
> 79 nfs_set_events(client);
> 80 }
>
> sometimes trigger and call nfs_service(POLLIN) eventhough the socket is
> not readable.
Does read() return -1/EAGAIN or 0?
If it returns 0, then this is expected: it means that the other side has
shutdown the socket's write-side. libnfs should either reconnect, or
disable POLLIN, treat all pending operations as aborted and stop
submitting more.
Paolo
> I verified this by adding an extra call to poll() at around line 78
> to check whether POLLIN was actually set on the fd or not. Sometimes it
> would not be but I got lost in the sources and could not find if or
> where this happens or even if qemu even guarantees "only call the POLLIN
> callbacks if the filedescriptor is actually readable".
>
