Messages in this thread Patch in this message | | | From | Yuyang Du <> | Subject | [PATCH v2 01/17] locking/lockdep: Add lock type enum to explicitly specify read or write locks | Date | Thu, 16 May 2019 15:59:59 +0800 |
| |
Add an enum to formalize lock types, as those type values now matter.
In order to make:
LOCK_TYPE_READ & LOCK_TYPE_RECURSIVE != 0
The recursive-read type is set to 3 as opposed to the current 2.
Signed-off-by: Yuyang Du <duyuyang@gmail.com> --- include/linux/lockdep.h | 45 +++++++++++++++++++++++++++++++++++++++------ include/linux/rcupdate.h | 2 +- kernel/locking/lockdep.c | 23 +++++++++++++---------- 3 files changed, 53 insertions(+), 17 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 7c2fefa..1009c47 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -339,10 +339,38 @@ static inline int lockdep_match_key(struct lockdep_map *lock, * * Values for "read": * - * 0: exclusive (write) acquire - * 1: read-acquire (no recursion allowed) - * 2: read-acquire with same-instance recursion allowed + * LOCK_TYPE_EXCLUSIVE (LOCK_TYPE_WRITE): exclusive (write) acquire + * LOCK_TYPE_READ: read-acquire (no recursion allowed) + * LOCK_TYPE_RECURSIVE: read-acquire with same-instance recursion allowed * + * The same lock between tasks have the following exclusiveness (the read + * type includes recursive read): + * + * read and read (no ) + * read and write (yes) + * write and write (yes) + * + * The enum values for the types are arranged such that: + * + * if type1 and type2 are exclusive then type1 & type2 == 0. + * + * We have a tricky situation concerning read vs. recursive-read. Since + * there can be lock classes that may ever be both read lock and + * recursive-read lock, for example: + * + * kernel/qrwlock.c:queued_read_lock_slowpath() + * + * The values of lock types are defined as follows: + */ +enum lock_type { + LOCK_TYPE_EXCLUSIVE = 0, + LOCK_TYPE_WRITE = 0, + LOCK_TYPE_READ, + LOCK_TYPE_UNUSED, + LOCK_TYPE_RECURSIVE, +}; + +/* * Values for check: * * 0: simple checks (freeing, held-at-exit-time, etc.) @@ -588,9 +616,14 @@ static inline void print_irqtrace_events(struct task_struct *curr) * on the per lock-class debug mode: */ -#define lock_acquire_exclusive(l, s, t, n, i) lock_acquire(l, s, t, 0, 1, n, i) -#define lock_acquire_shared(l, s, t, n, i) lock_acquire(l, s, t, 1, 1, n, i) -#define lock_acquire_shared_recursive(l, s, t, n, i) lock_acquire(l, s, t, 2, 1, n, i) +#define lock_acquire_exclusive(l, s, t, n, i) \ + lock_acquire(l, s, t, LOCK_TYPE_EXCLUSIVE, 1, n, i) + +#define lock_acquire_shared(l, s, t, n, i) \ + lock_acquire(l, s, t, LOCK_TYPE_READ, 1, n, i) + +#define lock_acquire_shared_recursive(l, s, t, n, i) \ + lock_acquire(l, s, t, LOCK_TYPE_RECURSIVE, 1, n, i) #define spin_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) #define spin_acquire_nest(l, s, t, n, i) lock_acquire_exclusive(l, s, t, n, i) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 922bb68..22b41b1 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -207,7 +207,7 @@ static inline void destroy_rcu_head_on_stack(struct rcu_head *head) { } static inline void rcu_lock_acquire(struct lockdep_map *map) { - lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); + lock_acquire(map, 0, 0, LOCK_TYPE_RECURSIVE, 0, NULL, _THIS_IP_); } static inline void rcu_lock_release(struct lockdep_map *map) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 7275d6c..fb6be63 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -2297,7 +2297,10 @@ static inline void inc_chains(void) * (Note that this has to be done separately, because the graph cannot * detect such classes of deadlocks.) * - * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read + * Returns: + * 0: on deadlock detected; + * 1: on OK; + * 3: LOCK_TYPE_RECURSIVE on recursive read */ static int check_deadlock(struct task_struct *curr, struct held_lock *next) @@ -2319,15 +2322,15 @@ static inline void inc_chains(void) * Allow read-after-read recursion of the same * lock class (i.e. read_lock(lock)+read_lock(lock)): */ - if ((next->read == 2) && prev->read) - return 2; + if ((next->read == LOCK_TYPE_RECURSIVE) && prev->read) + return LOCK_TYPE_RECURSIVE; /* * We're holding the nest_lock, which serializes this lock's * nesting behaviour. */ if (nest) - return 2; + return LOCK_TYPE_RECURSIVE; print_deadlock_bug(curr, prev, next); return 0; @@ -2407,7 +2410,7 @@ static inline void inc_chains(void) * write-lock never takes any other locks, then the reads are * equivalent to a NOP. */ - if (next->read == 2 || prev->read == 2) + if (next->read == LOCK_TYPE_RECURSIVE || prev->read == LOCK_TYPE_RECURSIVE) return 1; /* * Is the <prev> -> <next> dependency already present? @@ -2493,7 +2496,7 @@ static inline void inc_chains(void) * Only non-recursive-read entries get new dependencies * added: */ - if (hlock->read != 2 && hlock->check) { + if (hlock->read != LOCK_TYPE_RECURSIVE && hlock->check) { int ret = check_prev_add(curr, hlock, next, distance, &trace); if (!ret) @@ -2877,13 +2880,13 @@ static int validate_chain(struct task_struct *curr, * building dependencies (just like we jump over * trylock entries): */ - if (ret == 2) - hlock->read = 2; + if (ret == LOCK_TYPE_RECURSIVE) + hlock->read = LOCK_TYPE_RECURSIVE; /* * Add dependency only if this lock is not the head * of the chain, and if it's not a secondary read-lock: */ - if (!chain_head && ret != 2) { + if (!chain_head && ret != LOCK_TYPE_RECURSIVE) { if (!check_prevs_add(curr, hlock)) return 0; } @@ -4105,7 +4108,7 @@ static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip) curr->curr_chain_key = hlock->prev_chain_key; WARN(hlock->read, "downgrading a read lock"); - hlock->read = 1; + hlock->read = LOCK_TYPE_READ; hlock->acquire_ip = ip; if (reacquire_held_locks(curr, depth, i)) -- 1.8.3.1
| |