linux-kernel - [PATCH 05/17] locking/lockdep: Rename deadlock check functions

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Date:   Mon, 13 May 2019 17:11:51 +0800
From:   Yuyang Du <duyuyang@...il.com>
To:     peterz@...radead.org, will.deacon@....com, mingo@...nel.org
Cc:     bvanassche@....org, ming.lei@...hat.com, frederic@...nel.org,
        tglx@...utronix.de, boqun.feng@...il.com,
        linux-kernel@...r.kernel.org, Yuyang Du <duyuyang@...il.com>
Subject: [PATCH 05/17] locking/lockdep: Rename deadlock check functions

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 read locks,
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@...il.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 27ca55f..4adaf27 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1771,8 +1771,8 @@ static inline void set_lock_type2(struct lock_list *lock, int read)
  * 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);
@@ -2385,7 +2385,8 @@ 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 current
+ * context's held lock stack.
  *
  * (Note that this has to be done separately, because the graph cannot
  * detect such classes of deadlocks.)
@@ -2396,7 +2397,7 @@ static inline void inc_chains(void)
  *  2: LOCK_TYPE_RECURSIVE 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;
@@ -2480,7 +2481,7 @@ 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>.)
 	 *
@@ -2488,7 +2489,7 @@ 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;
 
@@ -2983,7 +2984,7 @@ 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