To add recursive read locks into the dependency graph, we need to store the types of dependencies for the BFS later. There are four kinds of dependencies:
* Non-recursive -> Non-recursive dependencies(NN) e.g. write_lock(prev) -> write_lock(next) * Recursive -> Non-recursive dependencies(RN) e.g. read_lock(prev) -> write_lock(next); * Non-recursive -> recursive dependencies(NR) e.g. write_lock(prev) -> read_lock(next); * Recursive -> recursive dependencies(RR) e.g. read_lock(prev) -> read_lock(next); Given a pair of two locks, four kinds of dependencies could all exist between them, so we use 4 bit for the presence of each kind(stored in lock_list::dep). Signed-off-by: Boqun Feng <boqun.f...@gmail.com> --- include/linux/lockdep.h | 2 ++ kernel/locking/lockdep.c | 46 ++++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 46 insertions(+), 2 deletions(-) diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index bfa8e0b0d6f1..35b3fc0d6793 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -192,6 +192,8 @@ struct lock_list { struct lock_class *class; struct stack_trace trace; int distance; + /* bitmap of different dependencies from head to this */ + u16 dep; /* * The parent field is used to implement breadth-first search, and the diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 86ef7ea9f79f..1220dab7a506 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -884,6 +884,7 @@ static int add_lock_to_list(struct lock_class *this, struct list_head *head, return 0; entry->class = this; + entry->dep = dep; entry->distance = distance; entry->trace = *trace; /* @@ -1024,6 +1025,33 @@ static inline bool bfs_error(enum bfs_result res) return res < 0; } +#define DEP_NN_BIT 0 +#define DEP_RN_BIT 1 +#define DEP_NR_BIT 2 +#define DEP_RR_BIT 3 + +#define DEP_NN_MASK (1U << (DEP_NN_BIT)) +#define DEP_RN_MASK (1U << (DEP_RN_BIT)) +#define DEP_NR_MASK (1U << (DEP_NR_BIT)) +#define DEP_RR_MASK (1U << (DEP_RR_BIT)) + +static inline unsigned int __calc_dep_bit(int prev, int next) +{ + if (prev == 2 && next != 2) + return DEP_RN_BIT; + if (prev != 2 && next == 2) + return DEP_NR_BIT; + if (prev == 2 && next == 2) + return DEP_RR_BIT; + else + return DEP_NN_BIT; +} + +static inline unsigned int calc_dep(int prev, int next) +{ + return 1U << __calc_dep_bit(prev, next); +} + static enum bfs_result __bfs(struct lock_list *source_entry, void *data, int (*match)(struct lock_list *entry, void *data), @@ -1951,6 +1979,16 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, if (entry->class == hlock_class(next)) { if (distance == 1) entry->distance = 1; + entry->dep |= calc_dep(prev->read, next->read); + } + } + + /* Also, update the reverse dependency in @next's ->locks_before list */ + list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) { + if (entry->class == hlock_class(prev)) { + if (distance == 1) + entry->distance = 1; + entry->dep |= calc_dep(next->read, prev->read); return 1; } } @@ -1978,14 +2016,18 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, */ ret = add_lock_to_list(hlock_class(next), &hlock_class(prev)->locks_after, - next->acquire_ip, distance, trace); + next->acquire_ip, distance, + calc_dep(prev->read, next->read), + trace); if (!ret) return 0; ret = add_lock_to_list(hlock_class(prev), &hlock_class(next)->locks_before, - next->acquire_ip, distance, trace); + next->acquire_ip, distance, + calc_dep(next->read, prev->read), + trace); if (!ret) return 0; -- 2.14.1