Messages in this thread | | | From | Andy Lutomirski <> | Subject | Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter | Date | Thu, 21 Nov 2019 13:01:08 -0800 |
| |
> On Nov 21, 2019, at 11:56 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, Nov 21, 2019 at 09:51:03AM -0800, Andy Lutomirski wrote: > >> Can we really not just change the lock asm to use 32-bit accesses for >> set_bit(), etc? Sure, it will fail if the bit index is greater than >> 2^32, but that seems nuts. > > There are 64bit architectures that do exactly that: Alpha, IA64. > > And because of the byte 'optimization' from x86 we already could not > rely on word atomicity (we actually play games with multi-bit atomicity > for PG_waiters and clear_bit_unlock_is_negative_byte).
I read a couple pages of the paper you linked and I didn’t spot what you’re talking about as it refers to x86. What are the relevant word properties of x86 bitops or the byte optimization?
| |