On Wed, 2017-07-12 at 07:37 -0400, Ilia Mirkin wrote: > On Wed, Jul 12, 2017 at 7:25 AM, Mike Galbraith <efa...@gmx.de> wrote: > > On Wed, 2017-07-12 at 11:55 +0200, Mike Galbraith wrote: > >> On Tue, 2017-07-11 at 14:22 -0400, Ilia Mirkin wrote: > >> > > >> > Some display stuff did change for 4.13 for GM20x+ boards. If it's not > >> > too much trouble, a bisect would be pretty useful. > >> > >> Bisection seemingly went fine, but the result is odd. > >> > >> e98c58e55f68f8785aebfab1f8c9a03d8de0afe1 is the first bad commit > > > > But it really really is bad. Looking at gitk fork in the road leading > > to it... > > > > 52d9d38c183b drm/sti:fix spelling mistake: "compoment" -> "component" - good > > e4e818cc2d7c drm: make drm_panel.h self-contained - good > > 9cf8f5802f39 drm: add missing declaration to drm_blend.h - good > > > > Before the git highway splits, all is well. The lane with commits > > works fine at both ends, but e98c58e55f68 is busted. Merge arfifact? > > Hmmm... that tree does not appear to have gotten a v4.12 backmerge at > any point. The last backmerge from Linus as far as I can tell was > v4.11-rc7. Could be an interaction with some out-of-tree change.
Ok, a network outage gave me time to go hunting. Indeed it is a bad interaction with the tree DRM merged into. All DRM did was to slip a WARN_ON_ONCE() that nouveau triggers into a kernel module where such things no longer warn, they blow the box out of the water. I made a dinky testcase module (attached), and bisected to the real root.... 19d436268dde95389c616bb3819da73f0a8b28a8 is the first bad commit commit 19d436268dde95389c616bb3819da73f0a8b28a8 Author: Peter Zijlstra <pet...@infradead.org> Date: Sat Feb 25 08:56:53 2017 +0100 debug: Add _ONCE() logic to report_bug() Josh suggested moving the _ONCE logic inside the trap handler, using a bit in the bug_entry::flags field, avoiding the need for the extra variable. Sadly this only works for WARN_ON_ONCE(), since the others have printk() statements prior to triggering the trap. Still, this saves a fair amount of text and some data: text data filename 10682460 4530992 defconfig-build/vmlinux.orig 10665111 4530096 defconfig-build/vmlinux.patched Suggested-by: Josh Poimboeuf <jpoim...@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Arnd Bergmann <a...@arndb.de> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Ingo Molnar <mi...@kernel.org> :040000 040000 9f47f66ec4c234f6ee8e2a09e991c95fe47cf2c1 3e92aa9e77b39ed075ae2c3bdf041d92ef898f62 M arch :040000 040000 34f70b73d40c82533dd7df9b289106be69e2fa8d dd5d7248694a36b3e170f2dca5d9c4121535a990 M include :040000 040000 f6e627b0d378f0a00d2987fdd0c7b215306e6e3c b360d4ee2579744cce530184d7dab13493f73ee0 M lib
--- kernel/Makefile | 2 ++ kernel/foo.c | 15 +++++++++++++++ 2 files changed, 17 insertions(+) --- a/kernel/Makefile +++ b/kernel/Makefile @@ -111,6 +111,8 @@ obj-$(CONFIG_MEMBARRIER) += membarrier.o obj-$(CONFIG_HAS_IOMEM) += memremap.o +obj-m += foo.o + $(obj)/configs.o: $(obj)/config_data.h targets += config_data.gz --- /dev/null +++ b/kernel/foo.c @@ -0,0 +1,15 @@ +#include <linux/module.h> +#include <linux/bug.h> + +static int __init foo_init(void) +{ + printk(KERN_INFO "foo: module loaded\n"); + WARN_ON_ONCE(1); + return 0; +} + +static void __exit foo_exit(void) { } + +module_init(foo_init); +module_exit(foo_exit); +MODULE_LICENSE("GPL");
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