On Tue Nov 21, 2023 at 5:18 AM AEST, John Snow wrote: > On Wed, Nov 15, 2023 at 12:23 PM Daniel P. Berrangé <berra...@redhat.com> > wrote: > > > > On Wed, Nov 15, 2023 at 01:14:53PM +0000, Daniel P. Berrangé wrote: > > > On Wed, Nov 15, 2023 at 07:23:01AM +0100, Thomas Huth wrote: > > > > On 15/11/2023 02.15, Nicholas Piggin wrote: > > > > > On Wed Nov 15, 2023 at 4:29 AM AEST, Thomas Huth wrote: > > > > > > On 14/11/2023 17.37, Philippe Mathieu-Daudé wrote: > > > > > > > On 14/11/23 17:31, Thomas Huth wrote: > > > > > > > > The tests seem currently to be broken. Disable them by default > > > > > > > > until someone fixes them. > > > > > > > > > > > > > > > > Signed-off-by: Thomas Huth <th...@redhat.com> > > > > > > > > --- > > > > > > > > tests/avocado/reverse_debugging.py | 7 ++++--- > > > > > > > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > > > > > > > > > > > Similarly, I suspect > > > > > > > https://gitlab.com/qemu-project/qemu/-/issues/1961 > > > > > > > which has a fix ready: > > > > > > > https://lore.kernel.org/qemu-devel/20231110170831.185001-1-richard.hender...@linaro.org/ > > > > > > > > > > > > > > Maybe wait the fix gets in first? > > > > > > > > > > > > No, I applied Richard's patch, but the problem persists. Does this > > > > > > test > > > > > > still work for you? > > > > > > > > > > I bisected it to 1d4796cd008373 ("python/machine: use socketpair() for > > > > > console connections"), > > > > > > > > Maybe John (who wrote that commit) can help? > > > > > > I find it hard to believe this commit is a direct root cause of the > > > problem since all it does is change the QEMU startup sequence so that > > > instead of QEMU listening for a monitor connection, it is given a > > > pre-opened monitor connection. > > > > > > At the very most that should affect the startup timing a little. > > > > > > I notice all the reverse debugging tests have a skip on gitlab > > > with a comment: > > > > > > # unidentified gitlab timeout problem > > > > > > this makes be suspicious that John's patch has merely made this > > > (henceforth undiagnosed) timeout more likely to ocurr. > > > > After an absolutely horrendous hours long debugging session I think > > I figured out the problem. The QEMU process is blocking in > > > > qemu_chr_write_buffer > > > > spinning in the loop on EAGAIN. > > > > The Python Machine() class has passed one of a pre-created socketpair > > FDs for the serial port chardev. The guest is trying to write to this > > and blocking. Nothing in the Machine() class is reading from the > > other end of the serial port console. > > > > > > Before John's change, the serial port uses a chardev in server mode > > and crucially 'wait=off', and the Machine() class never opened the > > console socket unless the test case wanted to read from it. > > > > IOW, QEMU had a background job setting there waiting for a connection > > that would never come. > > > > As a result when QEMU started executing the guest, all the serial port > > writes get sent into to the void. > > > > > > So John's patch has had a semantic change in behaviour, because the > > console socket is permanently open, and thus socket buffers are liable > > to fill up. > > > > As a demo I increased the socket buffers to 1MB and everything then > > succeeded. > > > > @@ -357,6 +360,10 @@ def _pre_launch(self) -> None: > > > > if self._console_set: > > self._cons_sock_pair = socket.socketpair() > > + self._cons_sock_pair[0].setsockopt(socket.SOL_SOCKET, > > socket.SO_SNDBUF, 1024*1024); > > + self._cons_sock_pair[0].setsockopt(socket.SOL_SOCKET, > > socket.SO_RCVBUF, 1024*1024); > > + self._cons_sock_pair[1].setsockopt(socket.SOL_SOCKET, > > socket.SO_SNDBUF, 1024*1024); > > + self._cons_sock_pair[1].setsockopt(socket.SOL_SOCKET, > > socket.SO_RCVBUF, 1024*1024); > > os.set_inheritable(self._cons_sock_pair[0].fileno(), True) > > > > # NOTE: Make sure any opened resources are *definitely* freed in > > > > > > The Machine class doesn't know if anything will ever use the console, > > so as is the change is unsafe. > > > > The original goal of John's change was to guarantee we capture early > > boot messages as some test need that. > > > > I think we need to be able to have a flag to say whether the caller needs > > an "early console" facility, and only use the pre-opened FD passing for > > that case. Tests we need early console will have to ask for that guarantee > > explicitly. > > Tch. I see. Thank you for diagnosing this. > > From the machine.py perspective, you have to *opt in* to having a > console, so I hadn't considered that a caller would enable the console > and then ... not read from it. Surely that's a bug in the caller? > > If you don't intend to read from the console, you shouldn't call > set_console().
Agree, hence the fix patch for the test case. Although most tests wait for console, ones like this that control the machine with gdb/qmp are rarer, so less examples to copy paste from. > > (The async rewrite I have been toying with on and off has a built-in > drainer that writes to a log file that would probably remedy this, but > the client tests should still be fixed, I think. Otherwise, do you This sounds good because no matter the test, you rarely don't want to log console output. Separating that from what the test does with console would be nice. > have any suggestions for how I might make this failure state more > obvious/friendly? I wonder if on close of the machine.py object I > could detect that the pipe is full and emit a warning about that.) That's an idea. It wouldn't be foolproof (test could be waiting for something else or failed for some other reason), but at least it could give a suggestion (similar to my warning in the chardev code). How would you do it? Maybe the simplest/portable way would be keep a pipe write fd open in the harness and try write something to it with O_NONBLOCK? Thanks, Nick
