I think we may also need an _atomic_unlock() to add a DMB during unlock as well.
On Wed, Jul 31, 2013 at 8:37 AM, Artturi Alm <artturi....@gmail.com> wrote: > On 07/31/13 08:57, Richard Allen wrote: >> >> Hi, >> >> I just wanted to let you know that _atomic_lock(), from _atomic_lock.c, >> as used by librthread should probably have a barrier instruction added >> to prevent the processor from reordering loads/stores around the >> atomic_lock. >> >> For more information about barriers on ARM, see: >> >> http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0489c/CIHGHHIE.html >> >> For some examples, see sections 7.2.1 and 7.2.2 >> >> http://infocenter.arm.com/help/topic/com.arm.doc.genc007826/Barrier_Litmus_Tests_and_Cookbook_A08.pdf >> >> -Richard >> > > Hi, > > I'm not sure what the diff against _atomic_lock.c would look like, > since i'm guessing it might not be supported, and i don't like > inline asm so i'll leave it to someone else, however, diff for > using it in cpufunc_asm_armv7.S would be something like below > > > -Artturi > > > > Index: cpufunc_asm_armv7.S > =================================================================== > RCS file: /cvs/src/sys/arch/arm/arm/cpufunc_asm_armv7.S,v > retrieving revision 1.6 > diff -u -p -r1.6 cpufunc_asm_armv7.S > --- cpufunc_asm_armv7.S 30 Mar 2013 01:30:30 -0000 1.6 > +++ cpufunc_asm_armv7.S 31 Jul 2013 13:26:18 -0000 > @@ -19,6 +19,7 @@ > #include <machine/asm.h> > > #define DSB .long 0xf57ff040 > +#define DMB .long 0xf57ff050 > #define ISB .long 0xf57ff060 > #define WFI .long 0xe320f003
