[launchd-dev] launchd and system sleep

[Thomas Clement]

On Jun 1, 2009, at 11:17 PM, Damien Sorresso wrote:

> On Jun 1, 2009, at 1:55 PM, Thomas Clement wrote:
>> Hello,
>>
>> The manual page for the "StartInterval" key mentions that "if the  
>> system is asleep, the job will be started the next time the  
>> computer wakes up".
>> However I'm receiving bug reports from users which seem to indicate  
>> this is not always the case (the job is not launched for a long  
>> period of time).
>> The problem does not seem to occur with the "StartCalendarInterval"  
>> key.
>
> There is a bug in the kernel which prevents timers from coalescing  
> after a wake from sleep (rdar://problem/4058640). launchd worked  
> around it for Leopard, but the workaround was only applied to  
> StartCalendarInterval, not StartInterval, apparently.

That bug number is low. I hope it will be fixed in 10.6.

>> I've also noticed the "com.apple.backupd-wake.plist" Time Machine  
>> job which is apparently triggered at wake time although it  
>> advertises no way to be launched. Why the need for this additional  
>> job since "com.apple.backupd-auto.plist" uses the "StartInterval"  
>> key? Is it a workaround for a launchd issue?
>
> That job is for when you turn on Time Machine backups from System  
> Preferences.

My understanding is that the "com.apple.backupd-auto.plist" job uses  
the StartInterval key and the "com.apple.backupd-wake.plist" job was  
added to work around bug 4058640. Since apparently Time Machine is not  
affected by the bug, I suspected this "backupd-wake" job was the  
workaround (else I don't see the point of this job).

>> Is this a known issue or am I missing something?
>> Can something be done about this?
>
> If it's feasible for you to switch to StartCalendarInterval, that  
> could be a temporary solution.

Thanks for your quick answer!


Regards,
Thomas