Re: Very early load and usage of higher level APIs
Re: Very early load and usage of higher level APIs
- Subject: Re: Very early load and usage of higher level APIs
- From: Shaun Wexler <email@hidden>
- Date: Fri, 9 Jun 2006 05:02:39 -0700
On Jun 8, 2006, at 10:56 PM, Ryan McGann wrote:
Now that the launchd discussion has died down, I guess it's time to
kick up the ashes with an honest question. We are using launchd in
Tiger to startup our daemon. It is currently not load-on-demand, so
it gets launched very early. It's usually process ID 18-25.
We seem to be experiencing some problems in Tiger related to how
early we get started. In particular, the following APIs seem to
rely on daemons to perform their dirty work, but those daemons are
not ready when we use them:
- The Carbon Alias Manager which is used to determine the location
of some files saved in the preferences accessed by our daemon.
Sometimes the Alias Manager fails to resolve the aliases, even
though they point to files that have not changed. We are using
FSResolveAliasNoUI to resolve the alias in our daemon.
Carbon is not daemon-safe, so you're SOL there. Tech Note 2083:
<http://developer.apple.com/technotes/tn2005/tn2083.html>
- The cdsa wrapper libCdsa, which fails sometimes in cdsaCspAttach
Both of these issues are reliably unreliable, in that they happen
every 1 out of 5 reboots or so. It took quite a bit of time to
narrow things down, but by adding a LOT of syslog statements, we
found that these two APIs randomly fail. Looking at the syslog and
process list in ps, I see that coreservicesd is launched very soon
after our daemon, so I am guessing that the Carbon File Manager
uses coreservicesd. I am *guessing* that the Security framework
uses securityd.
Since launchd has no dependancy list, how can I tell launchd that
we need these daemons launched *and ready* when our daemon loads?
Of course this won't work for services that are on-demand/inactive,
but how about something like this (untested, written in Mail):
#include <mach/mach_time.h>
#include <servers/bootstrap.h>
char *servicename[] = {
"com.apple.CoreServices.coreservicesd",
"com.apple.windowserver.active"
};
bootstrap_status_t serviceactive;
mach_timebase_info_data_t info;
(void)mach_timebase_info(&info);
uint64_t poll_interval = 1000000000ULL * info.denom / info.numer; //
1 second
uint32_t i = 0;
do {
while (bootstrap_status(bootstrap_port, servicename[i],
&serviceactive) == BOOTSTRAP_UNKNOWN_SERVICE && ! serviceactive) {
mach_wait_until(poll_interval + mach_absolute_time());
}
} while (++i < sizeof(servicename) / sizeof(servicename[0]));
HTH~
--
Shaun Wexler
MacFOH
http://www.macfoh.com
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