Re: PATCH: cdrecord: avoiding scsi device numbering for ide devices

[Con Kolivas]

Albert Cahalan writes:

> On Mon, 2004-08-09 at 18:59, Con Kolivas wrote:
> > Albert Cahalan writes:
> >
> >
> > > Joerg:
> > >    "WARNING: Cannot do mlockall(2).\n"
> > >    "WARNING: This causes a high risk for buffer underruns.\n"
> > > Fixed:
> > >    "Warning: You don't have permission to lock memory.\n"
> > >    "         If the computer is not idle, the CD may be ruined.\n"
> > > 
> > > Joerg:
> > >    "WARNING: Cannot set priority class parameters priocntl(PC_SETPARMS)\n"
> > >    "WARNING: This causes a high risk for buffer underruns.\n"
> > > Fixed:
> > >    "Warning: You don't have permission to hog the CPU.\n"
> > >    "         If the computer is not idle, the CD may be ruined.\n"
> >
> > Huh? That can't be right. Every cd burner this side of the 21st century has 
> > buffer underrun protection.
>
> I'm pretty sure my FireWire CD-RW/CD-R is from
> another century. Not that it's unusual in 2004.
>
> > I've burnt cds _while_ capturing and encoding 
> > video using truckloads of cpu and I/O without superuser privileges, had all 
> > the cdrecord warnings and didn't have a buffer underrun.
>
> That's cool. My hardware won't come close to that.
> Burning a coaster costs money.
>
> Let me put it this way: $$ $ $$$ $$ $ $$$ $$ $
>
> The warning, if re-worded, will save people from
> frustration and wasted money.

Sounds good; how about something less terrifying? That warning sounds like a 
ruined cd is likely.

> > Last time I gave 
> > superuser privilege to cdrecord it locked my machine - clearly it wasn't 
> > rt_task safe.
>
> So, you've been working on the scheduler anyway...
> An option to reserve some portion of CPU time for
> emergency use (say, 5% after 1 second has passed)
> would let somebody get out of this situation.

This breaks the real time policy entirely. That's why I run it SCHED_ISO ... 
but of course this isn't available in mainline linux.

> Reporting and/or fixing the cdrecord bug is nice too.

It was a hard lockup and randomly happened during a cd write, creating my 
first coaster in a long time... in rt mode ironically which is how it is 
recommended to be run. So I removed the foolish superuser bit and have had 
no problem since. Yes it was unaltered cdrecord source and it was the 
so-called alpha branch and... Not much else I can say about it really?

Cheers,
Con

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