On Thu, Apr 20, 2017 at 02:46:51PM -0700, Dan Williams wrote: > On Sat, Mar 18, 2017 at 2:52 AM, tip-bot for Kirill A. Shutemov > <tipbot@xxxxxxxxx> wrote: > > Commit-ID: 2947ba054a4dabbd82848728d765346886050029 > > Gitweb: http://git.kernel.org/tip/2947ba054a4dabbd82848728d765346886050029 > > Author: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > AuthorDate: Fri, 17 Mar 2017 00:39:06 +0300 > > Committer: Ingo Molnar <mingo@xxxxxxxxxx> > > CommitDate: Sat, 18 Mar 2017 09:48:03 +0100 > > > > x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation > > > > This patch provides all required callbacks required by the generic > > get_user_pages_fast() code and switches x86 over - and removes > > the platform specific implementation. > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Aneesh Kumar K . V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> > > Cc: Borislav Petkov <bp@xxxxxxxxx> > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > > Cc: Dann Frazier <dann.frazier@xxxxxxxxxxxxx> > > Cc: Dave Hansen <dave.hansen@xxxxxxxxx> > > Cc: H. Peter Anvin <hpa@xxxxxxxxx> > > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > Cc: Rik van Riel <riel@xxxxxxxxxx> > > Cc: Steve Capper <steve.capper@xxxxxxxxxx> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: linux-arch@xxxxxxxxxxxxxxx > > Cc: linux-mm@xxxxxxxxx > > Link: http://lkml.kernel.org/r/20170316213906.89528-1-kirill.shutemov@xxxxxxxxxxxxxxx > > [ Minor readability edits. ] > > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> > > I'm still trying to spot the bug, but bisect points to this patch as > the point at which my unit tests start failing with the following > signature: > > [ 35.423841] WARNING: CPU: 8 PID: 245 at lib/percpu-refcount.c:155 > percpu_ref_switch_to_atomic_rcu+0x1f5/0x200 Okay, I've tracked it down. The issue is triggered by replacment get_page() with page_cache_get_speculative(). page_cache_get_speculative() doesn't have get_zone_device_page(). :-| And I think it's your bug, Dan: it's wrong to have get_/put_zone_device_page() in get_/put_page(). I must be handled by page_ref_* machinery to catch all cases where we manipulate with page refcount. Back to the big picture: I hate that we need to have such additional code in page refcount primitives. I worked hard to remove compound page ugliness from there and now zone_device creeping in... Is it the only option? -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
