On Mon, 01 Sep 2014 01:15:12 +0300 Marko Rauhamaa firstname.lastname@example.org wrote:
If a signal is received when read() or write() has completed its task partially (> 0 bytes), no EINTR is returned but the partial count. Obviously, Python should take that possibility into account so that raising an exception in the signal handler (as mandated by the PEP) doesn't cause the partial result to be lost on os.read() or os.write().
If the signal handler is called, the exception *will* be raised. There's no guarantee at which point in the Python code it will be raised (it's implementation-dependent), but it's near impossible to protect regular Python code against such asynchronous exceptions.
Which is why you should switch to a wakeup fd scheme as mentioned by Victor, if you want to rely on signals at all.