On 8 Oct 2013, at 20:10, Hans de Goede wrote: > I noticed today that current qemu master would hang as soon as Xorg starts in > the guest when using qxl + a Linux guest. This message would be printed: > main-loop: WARNING: I/O thread spun for 1000 iterations > > And from then on the guest hangs and qemu consumes 100% cpu, bisecting pointed > out commit 7b595f35d89d73bc69c35bf3980a89c420e8a44b: > "aio / timers: Convert mainloop to use timeout" > > After looking at that commit I had a hunch the problem might be blocking > main_loop_wait calls being turned into non-blocking ones (and thus never > releasing the io-lock), a debug printf confirmed this was happening at > the moment of the hang, so I wrote this patch which fixes the hang for me > and seems like a good idea in general. > > Signed-off-by: Hans de Goede <hdego...@redhat.com> > --- > main-loop.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/main-loop.c b/main-loop.c > index c3c9c28..921c939 100644 > --- a/main-loop.c > +++ b/main-loop.c > @@ -480,6 +480,11 @@ int main_loop_wait(int nonblocking) > timerlistgroup_deadline_ns( > &main_loop_tlg)); > > + /* When not non-blocking always allow io-threads to acquire the lock */ > + if (timeout != 0 && timeout_ns == 0) { > + timeout_ns = 1; > + } > + > ret = os_host_main_loop_wait(timeout_ns); > qemu_iohandler_poll(gpollfds, ret); > #ifdef CONFIG_SLIRP
I /think/ you might mean "if (!blocking && timeout_ns == 0)" as timeout can be zero on a blocking call at this stage (i.e. when there is a timer which has already expired. I'm not entirely sure I understand the problem from your description - I'll answer this in your subseqent message. -- Alex Bligh