Messages in this thread | | | Date | Thu, 21 Jun 2018 22:37:53 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH 04/16] x86/split_lock: Use non locked bit set instruction in set_cpu_cap |
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On Thu, 21 Jun 2018, Peter Zijlstra wrote:
> On Sun, May 27, 2018 at 08:45:53AM -0700, Fenghua Yu wrote: > > set_bit() called by set_cpu_cap() is a locked bit set instruction for > > atomic operation. > > > > Since the c->x86_capability can span two cache lines depending on kernel > > configuration and building evnironment, the locked bit set instruction may > > cause #AC exception when #AC exception for split lock is enabled. > > That doesn't make sense. Sure the bitmap may be longer, but depending on > if the argument is an immediate or not we either use a byte instruction > (which can never cross a cacheline boundary) or a 'word' aligned BTS. > And the bitmap really _should_ be 'unsigned long' aligned. > > If it is not aligned, fix that too. > > /me looks at cpuinfo_x86 and finds x86_capability is in fact a __u32 > array.. see that's broken and needs fixing first.
Ditto for the next patch. ...
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