Re: [libvirt] [PATCH v3 3/5] tools: console: add missing locks in callbacks

On 4/4/19 2:57 AM, Nikolay Shirokovskiy wrote: > > > On 03.04.2019 23:44, Cole Robinson wrote: >> On 3/18/19 5:08 AM, Nikolay Shirokovskiy wrote: >>> Stream/fd callbacks accessing console object are called from the >>> event loop thread and the console object is also accessed from >>> the main thread so we are better add locking to handlers. >>> >>> Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy(a)virtuozzo.com&gt; >>> --- >>> tools/virsh-console.c | 35 +++++++++++++++++++++++++---------- >>> 1 file changed, 25 insertions(+), 10 deletions(-) >>> >> >> The qemuAgentIO and qemuMonitorIO callbacks also add have matching >> Ref/Unref calls along side the lock calls, but after scratching my head >> over it for a while I don't think it's necessary here: even if >> virConsoleShutdown is called from one of the callbacks, the main thread >> will still hold a reference until the callback releases the object lock >> > > We don't need even to rely on main thread. Event loop itself has a reference > which will be unrefed only after callback returns. > Hmm interesting, where in the code is that exactly? I know we pass a Free callback to virEventAddHandle but that's only called when the handle is removed, not after the callback is invoked. Maybe I'm missing something