Commit-ID: 154f185e9c0f6c50ac8e901630e14aa5b36f9414 Gitweb: https://git.kernel.org/tip/154f185e9c0f6c50ac8e901630e14aa5b36f9414 Author: Yuyang Du <[email protected]> AuthorDate: Mon, 6 May 2019 16:19:31 +0800 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 3 Jun 2019 11:55:47 +0200
locking/lockdep: Update comments on dependency search The breadth-first search is implemented as flat-out non-recursive now, but the comments are still describing it as recursive, update the comments in that regard. Signed-off-by: Yuyang Du <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/locking/lockdep.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 2e8ef6082f72..b2ca20aa69aa 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1381,6 +1381,10 @@ static inline struct list_head *get_dep_list(struct lock_list *lock, int offset) return lock_class + offset; } +/* + * Forward- or backward-dependency search, used for both circular dependency + * checking and hardirq-unsafe/softirq-unsafe checking. + */ static int __bfs(struct lock_list *source_entry, void *data, int (*match)(struct lock_list *entry, void *data), @@ -1461,12 +1465,6 @@ static inline int __bfs_backwards(struct lock_list *src_entry, } -/* - * Recursive, forwards-direction lock-dependency checking, used for - * both noncyclic checking and for hardirq-unsafe/softirq-unsafe - * checking. - */ - static void print_lock_trace(struct lock_trace *trace, unsigned int spaces) { unsigned long *entries = stack_trace + trace->offset; @@ -2285,7 +2283,7 @@ check_deadlock(struct task_struct *curr, struct held_lock *next, int read) /* * There was a chain-cache miss, and we are about to add a new dependency - * to a previous lock. We recursively validate the following rules: + * to a previous lock. We validate the following rules: * * - would the adding of the <prev> -> <next> dependency create a * circular dependency in the graph? [== circular deadlock] @@ -2335,11 +2333,12 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, /* * Prove that the new <prev> -> <next> dependency would not * create a circular dependency in the graph. (We do this by - * forward-recursing into the graph starting at <next>, and - * checking whether we can reach <prev>.) + * a breadth-first search into the graph starting at <next>, + * and check whether we can reach <prev>.) * - * We are using global variables to control the recursion, to - * keep the stackframe size of the recursive functions low: + * The search is limited by the size of the circular queue (i.e., + * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes + * in the graph whose neighbours are to be checked. */ this.class = hlock_class(next); this.parent = NULL;
