On Wed, 14 Nov 2012 11:41:49 -0800 Randy Dunlap rdunlap@infradead.org wrote:

On 11/13/2012 09:30 PM, Stephen Rothwell wrote:

...

Hi all,

News: next-20121115 (i.e. tomorrow) will be the last release until next-20121126 (which should be just be after -rc7, I guess - assuming that Linus does not release v3.7 before then), so if you want something in linux-next for a reasonable amount of testing, it should probably be committed tomorrow.

Changes since 20121113:

on i386:

ERROR: "__build_bug_on_failed" [drivers/gpu/drm/i915/i915.ko] undefined!

Reference to that symbol is found in i915_gem_execbuffer.o. Reference to BUILD_BUG_ON() is found in i915_gem_execbuffer.c:

static struct eb_objects * eb_create(int size) { struct eb_objects *eb; int count = PAGE_SIZE / sizeof(struct hlist_head) / 2; BUILD_BUG_ON(!is_power_of_2(PAGE_SIZE / sizeof(struct hlist_head)));

Where to start.

- eb_create() has no business assuming that the hlist_head has any particular size. We could easily add some conditionally-compiled debug fields in there, and drm blows up.

- The assertion is obviously true at present, so I assume that gcc screwed up and failed to reduce all that to a compile-time constant.

- We have a BUILD_BUG_ON_NOT_POWER_OF_2(). Use it?

- This code is using PAGE_SIZE to scale a kernel data structure. PAGE_SIZE can vary by a factor of 16, depending on Kconfig. This can result in 64k PAGE_SIZE machines exhibiting different beahviour from that which the testers saw.

Don't do it. It's better to hard-wire 4096.