Re: [RFC tip/locking/lockdep v5 04/17] lockdep: Introduce lock_list::dep

Boqun Feng
2018-02-24T07:27:36Z

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On Sat, Feb 24, 2018 at 01:32:50PM +0800, Boqun Feng wrote:
[...]
>
> I also reorder bit number for each kind of dependency, so that we have a
> simple __calc_dep_bit(), see the following:
>
> /*
> * DEP_*_BIT in lock_list::dep
> *
> * For dependency @prev -> @next:
> *
> * RR: both @prev and @next are recursive read locks, i.e. ->read == 2.
> * RN: @prev is recursive and @next is non-recursive.
> * NR: @prev is a not recursive and @next is recursive.
> * NN: both @prev and @next are non-recursive.
> *
> * Note that we define the value of DEP_*_BITs so that:
> * bit0 is prev->read != 2
> * bit1 is next->read != 2
> */
> #define DEP_RR_BIT 0
> #define DEP_RN_BIT 1
> #define DEP_NR_BIT 2

Oops, to make the following __cal_dep_bit() works, we should have:

#define DEP_NR_BIT 1
#define DEP_RN_BIT 2

instead.

Regards,
Boqun

> #define DEP_NN_BIT 3
>
> #define DEP_RR_MASK (1U << (DEP_RR_BIT))
> #define DEP_RN_MASK (1U << (DEP_RN_BIT))
> #define DEP_NR_MASK (1U << (DEP_NR_BIT))
> #define DEP_NN_MASK (1U << (DEP_NN_BIT))
>
> static inline unsigned int
> __calc_dep_bit(struct held_lock *prev, struct held_lock *next)
> {
> return (prev->read != 2) + ((next->read != 2) << 1)
> }
>
> static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
> {
> return 1U << __calc_dep_bit(prev, next);
> }
>

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