Re: [PATCH] bug in 2.4 bh_kmap_irq() breaks IDE under preempt patch

From: Jens Axboe (axboe@suse.de)
Date: Thu Mar 13 2003 - 05:28:54 EST

On Thu, Mar 13 2003, Marc-Christian Petersen wrote:
> On Thursday 13 March 2003 10:26, Jens Axboe wrote:
>
> Hi Jens,
>
> > There's a tiny bit missing from your patch:
> > > - * it's a highmem page
> > > - */
> > > - __cli();
> > > + local_irq_save(*flags);
> >
> > local_irq_disable();
> >
> > > addr = (unsigned long) kmap_atomic(bh->b_page, KM_BH_IRQ);
> > >
> > > - if (addr & ~PAGE_MASK)
> > > - BUG();
> > > + BUG_ON (addr & ~PAGE_MASK);
> > >
> > > return (char *) addr + bh_offset(bh);
> > > }
> > > @@ -58,7 +46,7 @@
> > > unsigned long ptr = (unsigned long) buffer & PAGE_MASK;
> > >
> > > kunmap_atomic((void *) ptr, KM_BH_IRQ);
> > > - __restore_flags(*flags);
> > > + local_irq_restore(*flags);
> local_irq_enable();
>
> ^ isn't this missing too with your suggested one-liner?

no, the local_irq_restore() brings back the irq flags from before we did
the irq disable. if interrupts were disabled before bh_kmap_irq() was
called, we must not enable them. basically, maintain the same flags. 

-- 
Jens Axboe

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

This archive was generated by hypermail 2b29 : Sat Mar 15 2003 - 22:00:34 EST