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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