On 24.09.24 01:56, Guenter Roeck wrote:
SPLIT_PTE_PTLOCKS depends on "NR_CPUS >= 4". Unfortunately, that evaluates
to true if there is no NR_CPUS configuration option. This results in
CONFIG_SPLIT_PTE_PTLOCKS=y for mac_defconfig. This in turn causes the m68k
"q800" and "virt" machines to crash in qemu if debugging options are
enabled.
Making CONFIG_SPLIT_PTE_PTLOCKS dependent on the existence of NR_CPUS
does not work since a dependency on the existence of a numeric Kconfig
entry always evaluates to false. Example:
config HAVE_NO_NR_CPUS
def_bool y
depends on !NR_CPUS
After adding this to a Kconfig file, "make defconfig" includes:
$ grep NR_CPUS .config
CONFIG_NR_CPUS=64
CONFIG_HAVE_NO_NR_CPUS=y
Define NR_CPUS for m68k instead to solve the problem.
Fixes: 394290cba966 ("mm: turn USE_SPLIT_PTE_PTLOCKS / USE_SPLIT_PTE_PTLOCKS into Kconfig options")
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
v2: Instead of trying to make SPLIT_PTE_PTLOCKS depend on the
existence of NR_CPUS, define NR_CPUS for m68k.
Okay, looks like we're cleaning up CONFIG_NR_CPUS for good.
I'm back from conference travel tomorrow; I'll then throw in the following
into cross compilers and fixup any other arch that needs attention:
diff --git a/include/linux/threads.h b/include/linux/threads.h
index 1674a471b0b4..e31715e6746b 100644
--- a/include/linux/threads.h
+++ b/include/linux/threads.h
@@ -13,8 +13,7 @@
* bit of memory. Use nr_cpu_ids instead of this except for static bitmaps.
*/
#ifndef CONFIG_NR_CPUS
-/* FIXME: This should be fixed in the arch's Kconfig */
-#define CONFIG_NR_CPUS 1
+#error "CONFIG_NR_CPUS not defined"
#endif
/* Places which use this should consider cpumask_var_t. */
--
Cheers,
David / dhildenb
