On Mon, Sep 02, 2013 at 07:44:39AM +0000, Wangyufei (A) wrote:
> Hello,
> When I ran programme event-test compiled from event-test.c, I found a problem that, after virEventRegisterDefaultImpl I do virConnectOpenAuth and virConnectClose, there will be handlers of socket and pipe opened by virConnectOpenAuth leaked after virConnectClose. So I did some analysis, and I found the fact following:
>
> In the condition that we only have one connection here
>
> int virNetSocketAddIOCallback(virNetSocketPtr sock,
> int events,
> virNetSocketIOFunc func,
> void *opaque,
> virFreeCallback ff)
> {
> int ret = -1;
>
> virObjectRef(sock); //Here we add sock refers once, then we will get refers equal 2 after
> virObjectLock(sock);
> if (sock->watch > 0) {
> VIR_DEBUG("Watch already registered on socket %p", sock);
> goto cleanup;
> }
>
> if ((sock->watch = virEventAddHandle(sock->fd, //If we have called virEventRegisterDefaultImpl, then here we'll get a sock watch non negative and will not go to cleanup.
> events,
> virNetSocketEventHandle,
> sock,
> virNetSocketEventFree)) < 0) {
> VIR_DEBUG("Failed to register watch on socket %p", sock);
> goto cleanup;
> }
> sock->func = func;
> sock->opaque = opaque;
> sock->ff = ff;
>
> ret = 0;
>
> cleanup:
> virObjectUnlock(sock);
> if (ret != 0)
> virObjectUnref(sock); //If we haven't called virEventRegisterDefaultImpl, we'll be here after virEventAddHandle, and sock refers will decrease to 1
> return ret;
> }
>
> Condition with virEventRegisterDefaultImpl, we'll do unrefer action in two places:
>
> 1. virEventRunDefaultImpl ->virEventPollRunOnce ->virEventRunDefaultImpl ->virEventPollRunOnce ->virEventPollCleanupHandles -> virNetSocketEventFree -> virObjectUnref
>
> 2. virConnectClose ->virObjectUnref ->virConnectDispose ->remoteConnectClose ->doRemoteClose ->virNetClientClose ->virNetClientCloseInternal -> virNetClientIOEventLoopPassTheBuck -> virNetClientCloseLocked -> virObjectUnref
>
> When event dealing loop is alive, everything work fine, we'll get sock refers 2
> after virConnectOpenAuth and unrefer twice in two places above after virConnectClose.
> But If some accidents happened like we quit event dealing loop or virEventRunDefaultImpl
> suspended, then sock refers will never be zero, and handlers will never be freed.
Do not stop running the event loop. It is a requirement of the API that once you have
called virEventRegisterDefaultImpl, you *must* always execute the event loop forever
after until your application exits.
> I consider to add something like virEventDeregisterDefaultImpl to set addHandleImpl and his buddy NULL. Apparently it is far away from fixing it completely.
No, stopping or de-registering event loop impls is a non-goal.
> At last I have two questions here:
>
>
> 1. Is it a problem that after virEventRegisterDefaultImpl we have handlers leaked?
There are no handlers leaked if you run the event loop, which is a requirement
of the API.
Daniel
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