* Juergen Gross <jgr...@suse.com> wrote:
> Some gcc versions seem to have problems with the constraints in > __cmpxchg_double() as they suddenly issue a build error when random > parts of sources calling __cmpxchg_double() are modified, like e.g. > slub.c. This has been observed on Debian systems only so far. > > Using "0" instead of "a" in the input constraints has the same > semantics while avoiding that build error. > > Signed-off-by: Juergen Gross <jgr...@suse.com> > --- > I should note that I have observed gcc hangs instead sometimes. Not > taking any patches modifying users of __cmpxchg_double() due to a gcc > bug which seems to be distro-specific is a bad move IMO. > > I'd rather make it clear from build behavior that this is a bug in gcc > by letting the build hang instead of throwing error warnings not in any > way related to changes in the code. > > The gcc bug is filed under: > > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=908154 > --- > arch/x86/include/asm/cmpxchg.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h > index a55d79b233d3..b3b4d61a8969 100644 > --- a/arch/x86/include/asm/cmpxchg.h > +++ b/arch/x86/include/asm/cmpxchg.h > @@ -245,7 +245,7 @@ extern void __add_wrong_size(void) > asm volatile(pfx "cmpxchg%c4b %2; sete %0" \ > : "=a" (__ret), "+d" (__old2), \ > "+m" (*(p1)), "+m" (*(p2)) \ > - : "i" (2 * sizeof(long)), "a" (__old1), \ > + : "i" (2 * sizeof(long)), "0" (__old1), \ > "b" (__new1), "c" (__new2)); \ This got changed to +a in -tip: c808c09b527c: x86/asm: Use CC_SET()/CC_OUT() in __cmpxchg_double() Mind sending a patch on top of -tip? Thanks, Ingo
