于 2011年01月04日 23:51, Eric Blake 写道:
On 01/04/2011 08:30 AM, Daniel P. Berrange wrote:
virDomainGetConnect (virDomainPtr dom) { - DEBUG("dom=%p", dom); + const char *name = virDomainGetName(dom); + + DEBUG("dom=%p, (VM: %s)", dom, NULLSTR(name));
Calling virDomainGetName() which is also a public API will pollute the logs with messages about virDomainGetName being invoked, every time.
So my fear about potential deadlock from invoking one public API from within another was not quite right, but I was on the right track of being worried about the use of a public API for debug purposes, because it does introduce log pollution. If this is the only problem, then a possible solution would be to use a private API for getting the name for logging purposes.
Logging the name alone is also potentially misleading, since most of the API impls use the UUID and ignore the name.
Then maybe the patch should be altered to output both name and UUID (probably by introducing a helper function, which when given a virDomainPtr outputs all three pieces of debug information rather than the current %p). I like the idea behind the patch, but only if we can come up with the correct way of getting the extra information when debugging is enabled, and without adding extra time when debugging is off. I'm not even sure what the right internal APIs for the job would be, or if they even exist yet.
Hi, Eric, I implemented a helper function like so in src/libvirt.c: static const char * virDomainNameUUID(virDomainPtr domain) { char *entry = NULL; const char *name = NULL; char uuidstr[VIR_UUID_STRING_BUFLEN]; if (!VIR_IS_DOMAIN(domain)) { entry = strdup("(VM: invalid domain)"); return entry; } name = domain->name; virUUIDFormat(domain->uuid, uuidstr); if(virAsprintf(&entry, "(VM: name=%s, uuid=%s)", name, uuidstr) < 0) virReportOOMError(); return NULLSTR(entry); } But how to avoid extra time when debugging is off? Following is not correct way definitely, as malloc'ed "entry" need to be freed. virConnectPtr virDomainGetConnect (virDomainPtr dom) { DEBUG("dom=%p, %s", dom, virDomainNameUUID(dom)); virResetLastError(); ...... } If do it like following: virConnectPtr virDomainGetConnect (virDomainPtr dom) { const char *name_uuid = virDomainUUID(dom); DEBUG("dom=%p, %s", dom, name_uuid); VIR_FREE(name_uuid); virResetLastError(); ...... } Then the extra time is introduced when debugging is off, do you have any good idea? Thanks Osier