On Wed, Jul 18, 2012 at 10:08:53PM +1000, Alexey Kardashevskiy wrote: > QEMU uses IO handlers to run select() in the main loop. > The handlers list is managed by qemu_set_fd_handler() helper > which works fine when called from the main thread as it is > called not when select() is waiting.
when select() is not waiting? > > However IO handlers list can be changed in the thread other than > the main one doing os_host_main_loop_wait(), for example, as a result > of a hypercall which changes PCI config space (VFIO on POWER is the case) So the problem is only with VFIO? Can it affect vhost-net? > and enables/disabled MSI/MSIX which closes/creates eventfd handles. There doesn't seem to be a notification in case an fd is deleted. It's probably not at all urgent to remove an fd from select - why do you mention closing handles? > If the main loop is waiting on such eventfd, it has to be restarted. Do you really mean 'should be waiting on the newly created eventfd'? > The patch adds the qemu_notify_event() call to interrupt select() > and make main_loop() to restart select() s/and make main_loop() to restart/to make main_loop() restart/? > with the updated IO > handlers list. > > Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> > Reviewed-by: Paolo Bonzini <pbonz...@redhat.com> > --- > iohandler.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/iohandler.c b/iohandler.c > index 3c74de6..dea4355 100644 > --- a/iohandler.c > +++ b/iohandler.c > @@ -77,6 +77,7 @@ int qemu_set_fd_handler2(int fd, > ioh->fd_write = fd_write; > ioh->opaque = opaque; > ioh->deleted = 0; > + qemu_notify_event(); > } > return 0; > } > -- > 1.7.10.4
