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[PATCH] Module per-cpu alignment cannot always be met 

Fwd from Daniel Drake <dsd@gentoo.org>.

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>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Rusty Russell 2005-08-10 13:52:38 +01:00 committed by Chris Wright
parent a3692f99ef
commit 24eda4e69d
1 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
kernel/module.c
View File

@ -249,13 +249,18 @@ static inline unsigned int block_size(int val)
/* 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++) {
@ -347,7 +352,8 @@ static int percpu_modinit(void)
}
__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;
}
@ -1554,7 +1560,8 @@ static struct module *load_module(void __user *umod,
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;