Re: [libvirt] PATCH: Prevent libvirtd 100% CPU usage when --timeout is used

On Wed, Feb 04, 2009 at 02:46:58PM +0000, Daniel P. Berrange wrote: > A couple of bugs conspired to make libvirtd use 100% CPU usage when the > --timeout option is used. This is the default for qemu:///session instance > which are auto-spawned, so quite annoying! > > eg libvirt --timeout=30 > > > - The qemudRunLoop() method was registering a timeout on every > iteration of the loop, when it considered itself inactive, > even if already registered > - virEventInteruptLocked() was looking at eventLoop.leader > and comparing to pthread_self() before anyone used the > event loop. 'leader' was 0 at this point so it thought it > had to wake someone up even though no one was waiting in > the event loop. > > The latter bug conspired with the former, so the act of registering > the timeout, caused it to immediately see a wakeup signal on the > following poll. So it did another loop iteration, adding another > timer, getting woken up again, etc 100% cpu follows. > > Another minor problem was that when completing an event loop > iteration, we reset eventloop.leader to '0'. It is not safe to > assume that pthread_t is an integer like this. The solution is > to track when something is using the event loop explicitly, and > not rely on the 'leader' variable, unless we know a thread is > active. > > Finally we never de-registered the shutdown timeout if a new > client turned up while we were counting down. > > This patch addresses all these flaws Opps, forgot to remove one chunk of redundant code that'd totally unregister the timer, when we only want to deactivate it now.