Re: [libvirt] [PATCH v5] Add functions for handling exponential backoff loops.

On Fri, Apr 15, 2016 at 16:45:07 +0200, Michal Privoznik wrote: > On 15.04.2016 13:53, Richard W.M. Jones wrote: > > In a few places in libvirt we busy-wait for events, for example qemu > > creating a monitor socket. This is problematic because: > > > > - We need to choose a sufficiently small polling period so that > > libvirt doesn't add unnecessary delays. > > > > - We need to choose a sufficiently large polling period so that > > the effect of busy-waiting doesn't affect the system. > > > > The solution to this conflict is to use an exponential backoff. > > > > This patch adds two functions to hide the details, and modifies a few > > places where we currently busy-wait. > > --- > > src/fdstream.c | 10 +++--- > > src/libvirt_private.syms | 2 ++ > > src/qemu/qemu_agent.c | 9 +++--- > > src/qemu/qemu_monitor.c | 10 +++--- > > src/util/virtime.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++ > > src/util/virtime.h | 11 +++++++ > > 6 files changed, 111 insertions(+), 12 deletions(-) > > ACK. Sorry for making you send v5 to such simple patch. GCC 5.3.0 doesn't like this very much: qemu/qemu_agent.c:238:8: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized] if (ret != 0) { qemu/qemu_monitor.c:369:8: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized] if (ret != 0) { The static analyzer considers the possibility that the while loop will never execute, which would be possible in a very strange lockup of the host.

Please initialize ret to -1 before pushing in those two functions.