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

From: jmerkey
Date: Fri Jan 27 2006 - 15:23:05 EST




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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