Re: [libvirt] [PATCHv2] util: ensure safe{read, write, zero} return is checked
On 03/09/2010 02:09 PM, Eric Blake wrote:
>> remoteDriverLock(priv);
>>
>> if (fds[1].revents) {
>> DEBUG0("Woken up from poll by other thread");
>> - saferead(priv->wakeupReadFD, &ignore, sizeof(ignore));
>> + ignore_value (saferead(priv->wakeupReadFD, &ignore,
>> + sizeof(ignore)));
>
> Hm. Are we sure we want to ignore the return value here? On the
> one hand, the fact that we failed to read this byte is irrelevant;
> it has done it's job to wake us out of poll. On the other hand,
> if we can't read this one byte, that probably means something more
> serious is wrong and we might (probably will?) have problems later.
> Should we goto error here?
Not the first instance of this; see, for example, daemon/event.c,
virEventHandleWakeup(). If we change how wakeups are handled, it should
be a separate patch, applied to all instances.
Yes and no. Yes, virEventHandleWakeup() does have a similar problem.
However, the callback function is an exported prototype, so we can't change it
to have a return value now (and though we might be able to play tricks with
the opaque pointer, we can't guarantee all callback users will follow
the tricks). Personally I would fix this one now and we could think about
the wakeup problem with virEventHandleWakeup() later, but I won't block
the patch for the (pretty minor) point.
--
Chris Lalancette