On Thu, 2015-04-02 at 16:04 +0100, Ian Jackson wrote: > The bootloader code is relying on detecting POLLHUP, and 7e9ec50b > breaks that. 7e9ec50b, when handling a pty master, violates the > specification of the datacopier interface (as defined). > > When the bootloader exits, several things change, all at once: > (a) The master pty fd (held by libxl) starts to signal POLLHUP > and maybe also POLLIN. > (b) The child exits (so that the SIGCHLD self-pipe signals POLLIN, > which will be handled by the libxl child process code. > (c) reads on the master pty fd start to return EOF > > From the point of view of the datacopier these might happen in any > order. I think there is a latent bug with (c), which I will discuss > later in this email.
later in another mail maybe? > In a recent bug report from a FreeBSD installation, the datacopier > gets told about (a) before (b). But 7e9ec50b filters the POLLHUP out, > so that the dc signals eof rather than hup. As a result in > bootloader_copyfail we take the error path. > > This reverts commit 7e9ec50b0535bf2630da9d279a060775817d136d. > > Signed-off-by: Ian Jackson <ian.jack...@eu.citrix.com> > CC: Andrew Cooper <andrew.coop...@citrix.com> > CC: Roger Pau Monné <roger....@citrix.com> Acked-by: Ian Campbell <ian.campb...@citrix.com> > CC: Ross Lagerwall <ross.lagerw...@citrix.com> > CC: Wei Liu <wei.l...@citrix.com> > --- > tools/libxl/libxl_aoutils.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c > index da102a0..3942634 100644 > --- a/tools/libxl/libxl_aoutils.c > +++ b/tools/libxl/libxl_aoutils.c > @@ -205,9 +205,6 @@ static void datacopier_readable(libxl__egc *egc, > libxl__ev_fd *ev, > libxl__datacopier_state *dc = CONTAINER_OF(ev, *dc, toread); > STATE_AO_GC(dc->ao); > > - if ((revents & (POLLHUP|POLLIN)) == (POLLHUP|POLLIN)) > - revents &= ~POLLHUP; > - > if (datacopier_pollhup_handled(egc, dc, revents, 0)) > return; > _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
