Re: 2.6.14 kernels and above copy_to_user stupidity with IRQ disabled check

[jmerkey@ns1.utah-nac.org]

OK.  Got it.  I guess I need to restructure.  And BTW, This was a code fragment
only, the spinlock gets released when -EFAULT is called -- was just an example.

Jeff

On Fri, Jan 27, 2006 at 03:18:06PM -0500, linux-os (Dick Johnson) wrote:
> 
> On Fri, 27 Jan 2006, Jeff V. Merkey wrote:
> 
> >
> > Is there a good reason someone set a disabled_irq() check on 2.6.14 and
> > above for copy_to_user to barf out
> > tons of bogus stack dump messages if the function is called from within
> > a spinlock:
> >
> 
> This is a joke, right????
> 
> > i.e.
> >
> > spin_lock_irqsave(&regen_lock, regen_flags);
> >    v = regen_head;
> >    while (v)
> >    {
> >       if (i >= count)
> >          return -EFAULT;
> 
> ** BUG **  return with spin-lock held!
> 
> >
> >
> >       err = copy_to_user(&s[i++], v, sizeof(VIRTUAL_SETUP));
> 
> ** BUG ** copy to user with spinlock held!
> 
> >       if (err)
> >          return err;
> >
> 
> ** BUG ** Return with spin-lock held!
> >
> >       v = v->next;
> >    }
> >    spin_unlock_irqrestore(&regen_lock, regen_flags);
> >
> > is now busted and worked in kernels up to this point.  The error message
> > is annoying but non-fatal.
> >
> > Jeff
> 
> It was NEVER supposed to work! The only reason it worked is because
> your page(s) copied to, were not swapped out. If they were swapped
> out, you are stuck, the page-fault won't occur.
> 
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.6.13.4 on an i686 machine (5589.66 BogoMips).
> Warning : 98.36% of all statistics are fiction.
> .
> 
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