On 16.01.2013 19:40, Daniel P. Berrange wrote: > On Wed, Jan 16, 2013 at 07:39:53PM +0100, Michal Privoznik wrote: >> On 16.01.2013 19:31, Daniel P. Berrange wrote: >>> On Wed, Jan 16, 2013 at 07:27:46PM +0100, Michal Privoznik wrote: >>>> Currently, whenever somebody calls saferead() on nonblocking FD >>>> (safewrite() is totally interchangeable for purpose of this >>>> message) he might get wrong return value. For instance, in the >>>> first iteration some data is read. The number of bytes read is >>>> stored into local variable 'nread'. However, in next iterations >>>> we can get -1 from read() with errno == EAGAIN, in which case the >>>> -1 is returned despite fact some data has already been read. So >>>> the caller gets confused. >>>> >>>> Moreover, the comment just above the functions says, they act >>>> like regular read() with nicer handling of EINTR. Well, they >>>> don't now. >>> >>> I think that it is correct that these APIs return -1 on EAGAIN. >>> These APIs should *not* be used on non-blocking FDs. >>> >> In that case I think we have to note it explicitly in the comments. > > BTW, what code did you encounter that was using this with non-blocking > fds ? > > Daniel > My new code which I am working on. Basically, from the event loop I was trying to read from a FD (hence a nonblocking FD) and I used saferead(fd, ...) instead of read(fd, ...). It took me a while to find out why am I not getting anything else than -1/EAGAIN. Michal -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list