Messages in this thread Patch in this message | | | Subject | Re: percpu_modalloc oops when loading netfilter modules | From | Rusty Russell <> | Date | Mon, 01 Aug 2005 15:27:17 +1000 |
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On Sat, 2005-07-30 at 00:48 +0100, Daniel Drake wrote: > Pete, Rusty, > > I found a snippet of a previous discussion of yours here: > > http://www.ussg.iu.edu/hypermail/linux/kernel/0408.3/2901.html > http://www.ussg.iu.edu/hypermail/linux/kernel/0409.0/0768.html > > Did anything become of this issue? > > A Gentoo user has reported what appears to be the same problem on 2.6.12: > http://bugs.gentoo.org/show_bug.cgi?id=97006
Name: Module per-cpu alignment cannot always be met. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (authored)
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
Index: linux-2.6.13-rc4-git3-Netfilter/kernel/module.c =================================================================== --- linux-2.6.13-rc4-git3-Netfilter.orig/kernel/module.c 2005-08-01 14:58:44.000000000 +1000 +++ linux-2.6.13-rc4-git3-Netfilter/kernel/module.c 2005-08-01 15:21:30.000000000 +1000 @@ -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; -- A bad analogy is like a leaky screwdriver -- Richard Braakman
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