From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: Re: linux-next: manual merge of the xen-tip tree with the tip tree Date: Wed, 12 Aug 2015 11:26:09 -0700 Message-ID: References: <20150812150954.36bc605c@canb.auug.org.au> <55CB49CA.8050305@oracle.com> <20150812172105.GW16853@twins.programming.kicks-ass.net> <20150812174625.GH18673@twins.programming.kicks-ass.net> <55CB8DAD.6090508@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <55CB8DAD.6090508@oracle.com> Sender: linux-next-owner@vger.kernel.org To: Boris Ostrovsky Cc: Peter Zijlstra , Stephen Rothwell , Jeremy Fitzhardinge , Konrad Rzeszutek Wilk , Stefano Stabellini , Xen Devel , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "linux-next@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Andy Lutomirski , David Vrabel List-Id: xen-devel@lists.xenproject.org On Wed, Aug 12, 2015 at 11:17 AM, Boris Ostrovsky wrote: > On 08/12/2015 01:46 PM, Peter Zijlstra wrote: >> >> On Wed, Aug 12, 2015 at 07:21:05PM +0200, Peter Zijlstra wrote: >>> >>> On Wed, Aug 12, 2015 at 09:27:38AM -0400, Boris Ostrovsky wrote: >>> >>>> Incidentally, 11276d53 ("locking/static_keys: Add a new static_key >>>> interface") breaks old-ish compilers (gcc version 4.4.4 20100503 (= Red >>>> Hat >>>> 4.4.4-2) (GCC)): >>>> >>>> >>>> >>>> CC arch/x86/kernel/nmi.o >>>> In file included from >>>> /home/build/linux-boris/include/linux/jump_label.h:109, >>>> from >>>> /home/build/linux-boris/arch/x86/include/asm/spinlock.h:5, >>>> from >>>> /home/build/linux-boris/include/linux/spinlock.h:88, >>>> from /home/build/linux-boris/arch/x86/kernel/nmi= =2Ec:14: >>>> /home/build/linux-boris/arch/x86/include/asm/jump_label.h: In func= tion >>>> =E2=80=98nmi_handle=E2=80=99: >>>> /home/build/linux-boris/arch/x86/include/asm/jump_label.h:21: warn= ing: >>>> asm >>>> operand 0 probably doesn=E2=80=99t match constraints >>>> /home/build/linux-boris/arch/x86/include/asm/jump_label.h:21: erro= r: >>>> impossible constraint in =E2=80=98asm=E2=80=99 >>>> make[3]: *** [arch/x86/kernel/nmi.o] Error 1 >>>> make[2]: *** [arch/x86/kernel] Error 2 >>>> make[1]: *** [arch/x86] Error 2 >>> >>> Ugh bugger. >>> >>> I bet its that: &((char *)key)[branch] business, an earlier variant >>> thereof tripped up more recent GCCs too. >>> >>> So its an __always_inline function, and both argument are always co= mpile >>> time constants, @key is the address of an object in static storage = (a >>> global) and @branch is a simple 0/1 at the call site. >>> >>> Now we wish to compute (unsigned long)key + branch at compile/link = time >>> to feed to the assembler as an immediate, which should be possible, >>> given its all 'constants'. >>> >>> It just appears GCC is having a hard time with this. >>> >>> Let me see if I have a sufficiently old GCC around to play with. >> >> Could you feed the below to your compiler? Its a bit cumbersome, but >> its the next best I could come up with... > > > No, it produces the same error. This is Fedora 13, btw, uses gcc 4.4.= 4. Is the problem just that it's being misdetected as supporting asm goto? What does gcc -E say? --Andy