[PATCH] Module per-cpu alignment cannot always be met
The module code assumes noone will ever ask for a per-cpu area more than
SMP_CACHE_BYTES aligned. However, as these cases show, gcc asks sometimes
asks for 32-byte alignment for the per-cpu section on a module, and if
CONFIG_X86_L1_CACHE_SHIFT is 4, we hit that BUG_ON(). This is obviously an
unusual combination, as there have been few reports, but better to warn
than die.
See:
http://www.ussg.iu.edu/hypermail/linux/kernel/0409.0/0768.html
And more recently:
http://bugs.gentoo.org/show_bug.cgi?id=97006
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/module.c b/kernel/module.c
index 068e271..c32995f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -250,13 +250,18 @@
/* Created by linker magic */
extern char __per_cpu_start[], __per_cpu_end[];
-static void *percpu_modalloc(unsigned long size, unsigned long align)
+static void *percpu_modalloc(unsigned long size, unsigned long align,
+ const char *name)
{
unsigned long extra;
unsigned int i;
void *ptr;
- BUG_ON(align > SMP_CACHE_BYTES);
+ if (align > SMP_CACHE_BYTES) {
+ printk(KERN_WARNING "%s: per-cpu alignment %li > %i\n",
+ name, align, SMP_CACHE_BYTES);
+ align = SMP_CACHE_BYTES;
+ }
ptr = __per_cpu_start;
for (i = 0; i < pcpu_num_used; ptr += block_size(pcpu_size[i]), i++) {
@@ -348,7 +353,8 @@
}
__initcall(percpu_modinit);
#else /* ... !CONFIG_SMP */
-static inline void *percpu_modalloc(unsigned long size, unsigned long align)
+static inline void *percpu_modalloc(unsigned long size, unsigned long align,
+ const char *name)
{
return NULL;
}
@@ -1644,7 +1650,8 @@
if (pcpuindex) {
/* We have a special allocation for this section. */
percpu = percpu_modalloc(sechdrs[pcpuindex].sh_size,
- sechdrs[pcpuindex].sh_addralign);
+ sechdrs[pcpuindex].sh_addralign,
+ mod->name);
if (!percpu) {
err = -ENOMEM;
goto free_mod;
