On Wed, 15 Sep 2010 11:16:24 pm Amit Shah wrote: > On (Wed) Sep 15 2010 [15:37:21], Hans de Goede wrote: > > >>--- linux-2.6.35.x86_64/drivers/char/virtio_console.c~ 2010-08-02 > > >>00:11:14.000000000 +0200 > > >>+++ linux-2.6.35.x86_64/drivers/char/virtio_console.c 2010-09-15 > > >>13:39:29.043505000 +0200 > > >>@@ -642,7 +642,7 @@ static unsigned int port_fops_poll(struc > > >> poll_wait(filp,&port->waitqueue, wait); > > >> > > >> ret = 0; > > >>- if (port->inbuf) > > >>+ if (!will_read_block(port)) > > > > > >Looks correct, but this should be > > > > > > if (port_has_data(port)) > > > > > >instead. > > > > That certainly works for me (as in will still fix the bug I'm hitting), but > > quoting from "man 2 select": > > > > Three independent sets of file descriptors are watched. Those > > listed > > in readfds will be watched to see if characters become available > > for > > reading (more precisely, to see if a read will not block; in > > particu‐ > > lar, a file descriptor is also ready on end-of-file) > > > > Notice the "a file descriptor is also ready on end-of-file", and > > port_fops_read treats the host not being connected as eof (it returns 0 > > in that case). So from an API pov I'm not sure what is correct. > > poll(2) says: > > POLLIN There is data to read. > > That makes it simple.
That's a documentation bug. On a pipe, POLLIN is set when the other end closes. read() then returns 0 immediately. poll() sets POLLIN when read() won't block, and people count on it. Let's do that, please. Rusty. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
