On Tue, 12 Nov 2019, Daniel Wagner wrote:
> [cc: linux-user-rt, Thomas and Sebastian]
>
> On Mon, Nov 11, 2019 at 08:59:44AM -0500, Mikulas Patocka wrote:
> > list_bl.h would crash with BUG() if we used it without locking.
> > dm-snapshot uses its own locking on readltime kernels, so to avoid this
> > BUG, we must set LIST_BL_LOCKMASK = 0.
> >
> > Signed-off-by: Mikulas Patocka <[email protected]>
> >
> > Index: linux-rt-devel/include/linux/list_bl.h
> > ===================================================================
> > --- linux-rt-devel.orig/include/linux/list_bl.h 2019-11-07
> > 14:01:51.000000000 +0100
> > +++ linux-rt-devel/include/linux/list_bl.h 2019-11-08 10:12:49.000000000
> > +0100
> > @@ -19,7 +19,7 @@
> > * some fast and compact auxiliary data.
> > */
> >
> > -#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
> > +#if (defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)) &&
> > !defined(CONFIG_PREEMPT_RT_BASE)
>
> CONFIG_PREEMPT_RT_BASE is only available in the out of tree -rt patch
> set, therefore I assume it's not for mainline, right?
Yes - this is intended to be applied to the realtime patchset.
Mikulas
> > #define LIST_BL_LOCKMASK 1UL
> > #else
> > #define LIST_BL_LOCKMASK 0UL
> > @@ -161,9 +161,6 @@ static inline void hlist_bl_lock(struct
> > bit_spin_lock(0, (unsigned long *)b);
> > #else
> > raw_spin_lock(&b->lock);
> > -#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
> > - __set_bit(0, (unsigned long *)b);
> > -#endif
> > #endif
> > }
> >
> > @@ -172,9 +169,6 @@ static inline void hlist_bl_unlock(struc
> > #ifndef CONFIG_PREEMPT_RT_BASE
> > __bit_spin_unlock(0, (unsigned long *)b);
> > #else
> > -#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
> > - __clear_bit(0, (unsigned long *)b);
> > -#endif
> > raw_spin_unlock(&b->lock);
> > #endif
> > }
> >
> > --
> > dm-devel mailing list
> > [email protected]
> > https://www.redhat.com/mailman/listinfo/dm-devel
> >
>
> Thanks,
> Daniel
>
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