Re: [Bug-wget] gnutls_handshake can return GNUTLS_E_INTERRUPTED

[Tim Ruehsen]

On Thursday 30 June 2016 17:18:36 Daniel Stenberg wrote:
> On Thu, 30 Jun 2016, Tim Ruehsen wrote:
> > I believe, we already handle that case. If GNUTLS_E_INTERRUPTED occurs, we
> > restart the loop and re-enter gnutls_handshake(). This happens for all
> > non-fatal errors.
> 
> Right, but then it won't wait for the socket and just busy-loop. The
> gnutls_record_get_direction man page[*] seems to suggest that waiting for
> the socket is the appropriate way:
> 
>   This function provides information about the internals of the record
> protocol and is only useful if a prior gnutls function call (e.g.
> gnutls_handshake()) was interrupted for some reason, that is, if a function
> returned GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN. In such a case, you might
> want to call select() or poll() before calling the interrupted gnutls
> function again
> 
> [*] = http://linux.die.net/man/3/gnutls_record_get_direction

GNUTLS_E_INTERRUPTED is returned if the process got a signal that interrupts 
blocking I/O (for wget this is SIGUSR1 and SIGHUP). If it is just *one* signal 
(very likely), a successive call to gnutls_handshake() would not return again 
with this value.
If the process gets 'hammered' by signals, we have a busy-loop. But with your 
change, the poll/wait would also immediate return with errno=EINTR - and we 
have a busy-loop as well.

So from what I can judge, your change adds 'complexity' without any gain.

Tim

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