Re: Fwd: I would like to cancel archive creation

Johnathan Burchill wrote:
> On June 19, 2004 09:59 am, Johnathan Burchill wrote:
> 
>>Hi Denis,

Hello Johnathan,

>>
>>I received this from a kdar user who asks whether it is possible to
>>cancel a libdar operation. My first attempt will be to add the "dry-run"
>>feature to the creation process. However, this is not a "quick" test of
>>the backup, I think it takes a time comparable to the actual backup. Is
>>this right?

I think this is faster, but I have not made real comparison ;-)

>>
>>As far as interrupting the creation process, now that libdar is
>>thread-safe, would there be a way to send it a "kill" signal, to get it
>>to stop what it is doing? A couple of people have asked for this
>>feature.

does a SIGTERM handler would help ? There is a mutex to release, file 
descriptors to close, and memory to release. I suspect Linux closes file 
descriptors let openned by the thread, but it cannot obviously be done 
the same for mutex (which are shared by all threads). For other system I 
don't know what's the behavior about file descriptors.

> 
> 
> QT has a method for terminating a thread, but this warning comes with the 
> documentation:
> 
> Warning: This function is dangerous, and its use is discouraged. The thread 
> can be terminate at any point in its code path. Threads can be terminated 
> while modifying data. There is no chance for the thread to cleanup after 
> itself, unlock any held mutexes, etc. In short, use this function only if 
> absolutely necessary. (from http://doc.trolltech.com/3.3/qthread.html)
> 
> For the command line dar, a <Ctrl>-C will interrupt the libdar operation. 
> I'm guessing that the terminate method is the equivalent for the QT GUI 
> version. In dar-2.1.3, the library is not thread safe, so I only run one 
> operation at a time, and killing the operation shouldn't be problematic as 
> there are no locked mutexes. This should be like hitting <Ctrl>-C.
> But the new threadsafe library may have issues with this technique.

yes.

> 
> Any comments?

What standard mechanism over signal handlers can preempt a thread and 
let it do some arbitrary action ? I don't like polling. :-/

> 
> Cheers,
> JB

Cheers,
Denis.



-------------------------------------------------------
This SF.Net email is sponsored by The 2004 JavaOne(SM) Conference
Learn from the experts at JavaOne(SM), Sun's Worldwide Java Developer
Conference, June 28 - July 1 at the Moscone Center in San Francisco, CA
REGISTER AND SAVE! http://java.sun.com/javaone/sf Priority Code NWMGYKND