[PATCH v3 01/30] locking/lockdep: Rename deadlock check functions

Yuyang Du
2019-06-28T09:15:50Z

Deadlock checks are performed at two places:

- Within current's held lock stack, check for lock recursion deadlock.
- Within dependency graph, check for lock inversion deadlock.

Rename the two relevant functions for later use. Plus, with
recursive-read locks, only a dependency circle in graph is not a
sufficient condition for lock inversion deadlocks anymore, so
check_noncircular() is not entirely accurate.

No functional change.

Signed-off-by: Yuyang Du <duyuyang@gmail.com>
---
kernel/locking/lockdep.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 341f521..e30e9e4 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1714,8 +1714,8 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class)
* Print an error and return 0 if it does.
*/
static noinline int
-check_noncircular(struct held_lock *src, struct held_lock *target,
- struct lock_trace *trace)
+check_deadlock_graph(struct held_lock *src, struct held_lock *target,
+ struct lock_trace *trace)
{
int ret;
struct lock_list *uninitialized_var(target_entry);
@@ -2302,7 +2302,8 @@ static inline void inc_chains(void)
}

/*
- * Check whether we are holding such a class already.
+ * Check whether we are holding such a class already in the current
+ * held lock stack.
*
* (Note that this has to be done separately, because the graph cannot
* detect such classes of deadlocks.)
@@ -2310,7 +2311,7 @@ static inline void inc_chains(void)
* Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
*/
static int
-check_deadlock(struct task_struct *curr, struct held_lock *next)
+check_deadlock_current(struct task_struct *curr, struct held_lock *next)
{
struct held_lock *prev;
struct held_lock *nest = NULL;
@@ -2394,7 +2395,7 @@ static inline void inc_chains(void)

/*
* Prove that the new <prev> -> <next> dependency would not
- * create a circular dependency in the graph. (We do this by
+ * create a deadlock scenario in the graph. (We do this by
* a breadth-first search into the graph starting at <next>,
* and check whether we can reach <prev>.)
*
@@ -2402,7 +2403,7 @@ static inline void inc_chains(void)
* MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
* in the graph whose neighbours are to be checked.
*/
- ret = check_noncircular(next, prev, trace);
+ ret = check_deadlock_graph(next, prev, trace);
if (unlikely(ret <= 0))
return 0;

@@ -2878,7 +2879,7 @@ static int validate_chain(struct task_struct *curr,
* The simple case: does the current hold the same lock
* already?
*/
- int ret = check_deadlock(curr, hlock);
+ int ret = check_deadlock_current(curr, hlock);

if (!ret)
return 0;
--
1.8.3.1