Messages in this thread | | | Date | Thu, 30 Jun 2016 14:59:19 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/5] lockdep: Implement bitlock map allocator |
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On Mon, Jun 20, 2016 at 01:55:11PM +0900, Byungchul Park wrote:
> +struct bitlock_map { > + struct hlist_node hash_entry; > + unsigned long bitaddr; /* ID */ > + struct lockdep_map map; > + int ref; /* reference count */ > +};
So this is effectively bigger than just adding a struct lockdep_map into whatever structure holds the bit spinlock to begin with.
What is the gain?
> +static inline unsigned long get_bitaddr(int bitnum, unsigned long *addr) > +{ > + return (unsigned long)((char *)addr + bitnum); > +}
And given you keep these lockdep_map thingies out-of-line, the original structure remains dense and thus the above munging can easily result in collisions.
Now, I suppose its rather unlikely, but given its entirely silent if it happens, this is bad.
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