list_bl would crash with BUG() if we used it without locking. dm-snapshot uses its own locking on realtime kernels (it can't use list_bl because list_bl uses raw spinlock and dm-snapshot takes other non-raw spinlocks while holding bl_lock).
To avoid this BUG, we must set LIST_BL_LOCKMASK = 0. This patch is intended only for the realtime kernel patchset, not for the upstream kernel. Signed-off-by: Mikulas Patocka <[email protected]> --- include/linux/list_bl.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-rt-devel/include/linux/list_bl.h =================================================================== --- linux-rt-devel.orig/include/linux/list_bl.h 2019-11-13 12:15:50.000000000 +0100 +++ linux-rt-devel/include/linux/list_bl.h 2019-11-13 12:15:50.000000000 +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) #define LIST_BL_LOCKMASK 1UL #else #define LIST_BL_LOCKMASK 0UL -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
