Amos Kong <ak...@redhat.com> reported that file descriptors numbered higher than 1024 could crash QEMU. This is due to the fixed size of the fd_set type used for select(2) event polling.
This series converts the main-loop.c and aio-posix.c select(2) calls to g_poll(3). This eliminates the fd_set type and allows QEMU to scale to high numbers of file descriptors. The g_poll(3) interface is a portable version of the poll(2) system call. The difference to select(2) is that fine-grained events (G_IO_IN, G_IO_OUT, G_IO_HUP, G_IO_ERR, G_IO_PRI) can be monitored instead of just read/write/exception. Also, there is no limit to the file descriptor numbers that may be used, allowing applications to scale to many file descriptors. See the documentation for details: http://developer.gnome.org/glib/2.28/glib-The-Main-Event-Loop.html#g-poll The QEMU main loop works as follows today: 1. Call out to slirp, iohandlers, and glib sources to fill rfds/wfds/xfds with the file descriptors to select(2). 2. Perform the select(2) call. 3. Call out to slirp, iohandlers, and glib sources to handle events polled in rfds/wfds/xfds. The plan of attack is as follows: 1. Replace select(2) with g_poll(3). Use glue that converts between rfds/wfds/xfds and GPollFD so that the unconverted QEMU components still work. 2. Convert slirp, iohandlers, and glib source fill/poll functions to use GPollFD directly instead of rfds/wfds/xfds. 3. Drop the glue since all components now natively use GPollFD. 4. Convert aio-posix.c to g_poll(3) by reusing GPollFD. I have tested that the series builds and is bisectable on Linux and Windows hosts. But I have not done extensive testing on other host platforms or with long-term guests to check for performance regressions. v2: * Replace custom Poller type with GArray [aliguori] Stefan Hajnoczi (9): main-loop: fix select_ret uninitialized variable warning main-loop: switch to g_poll() on POSIX hosts main-loop: switch POSIX glib integration to GPollFD slirp: switch to GPollFD iohandler: switch to GPollFD main-loop: drop rfds/wfds/xfds for good aio: extract aio_dispatch() from aio_poll() aio: convert aio_poll() to g_poll(3) aio: support G_IO_HUP and G_IO_ERR aio-posix.c | 130 ++++++++++++++++++--------------------- async.c | 2 + include/block/aio.h | 3 + include/qemu/main-loop.h | 4 +- iohandler.c | 40 +++++++++--- main-loop.c | 156 ++++++++++++++++++++++++++--------------------- slirp/libslirp.h | 6 +- slirp/main.h | 1 - slirp/slirp.c | 136 ++++++++++++++++++++++++----------------- slirp/socket.c | 9 --- slirp/socket.h | 2 + stubs/slirp.c | 6 +- 12 files changed, 270 insertions(+), 225 deletions(-) -- 1.8.1
