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From: Yuyang Du <duyuyang@gmail.com>
To: peterz@infradead.org, will.deacon@arm.com, mingo@kernel.org
Cc: bvanassche@acm.org, ming.lei@redhat.com, frederic@kernel.org,
	tglx@linutronix.de, boqun.feng@gmail.com,
	linux-kernel@vger.kernel.org, Yuyang Du <duyuyang@gmail.com>
Subject: [PATCH 01/17] locking/lockdep: Add lock type enum to explicitly specify read or write locks
Date: Mon, 13 May 2019 17:11:47 +0800	[thread overview]
Message-ID: <20190513091203.7299-2-duyuyang@gmail.com> (raw)
In-Reply-To: <20190513091203.7299-1-duyuyang@gmail.com>

Add an enum to formalize lock types, as those type values now matter. No
functional change.

Signed-off-by: Yuyang Du <duyuyang@gmail.com>
---
 include/linux/lockdep.h  | 28 ++++++++++++++++++++++------
 kernel/locking/lockdep.c | 23 +++++++++++++----------
 2 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 7c2fefa..441288c 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -339,10 +339,21 @@ 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
  *
+ * Note that we have an assumption that a lock class cannot ever be both
+ * read and recursive-read.
+ */
+enum lock_type {
+	LOCK_TYPE_EXCLUSIVE	= 0,
+	LOCK_TYPE_WRITE		= 0,
+	LOCK_TYPE_READ,
+	LOCK_TYPE_RECURSIVE,
+};
+
+/*
  * Values for check:
  *
  *   0: simple checks (freeing, held-at-exit-time, etc.)
@@ -588,9 +599,14 @@ 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/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 7275d6c..e9eafcf 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;
+ *  2: 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


  reply	other threads:[~2019-05-13  9:13 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-13  9:11 [PATCH 00/17] Support for read-write lock deadlock detection Yuyang Du
2019-05-13  9:11 ` Yuyang Du [this message]
2019-05-13 11:45   ` [PATCH 01/17] locking/lockdep: Add lock type enum to explicitly specify read or write locks Peter Zijlstra
2019-05-14  1:31     ` Yuyang Du
2019-05-14 12:04       ` Peter Zijlstra
2019-05-13  9:11 ` [PATCH 02/17] locking/lockdep: Add read-write type for dependency Yuyang Du
2019-05-13  9:11 ` [PATCH 03/17] locking/lockdep: Add helper functions to operate on the searched path Yuyang Du
2019-05-13  9:11 ` [PATCH 04/17] locking/lockdep: Update direct dependency's read-write type if it exists Yuyang Du
2019-05-13  9:11 ` [PATCH 05/17] locking/lockdep: Rename deadlock check functions Yuyang Du
2019-05-13  9:11 ` [PATCH 06/17] locking/lockdep: Adjust BFS algorithm to support multiple matches Yuyang Du
2019-05-13  9:11 ` [PATCH 07/17] locking/lockdep: Introduce mark_lock_unaccessed() Yuyang Du
2019-05-13  9:11 ` [PATCH 08/17] locking/lockdep: Introduce chain_hlocks_type for held lock's read-write type Yuyang Du
2019-05-13  9:11 ` [PATCH 09/17] locking/lockdep: Hash held lock's read-write type into chain key Yuyang Du
2019-05-13  9:11 ` [PATCH 10/17] locking/lockdep: Support read-write lock's deadlock detection Yuyang Du
2019-05-13  9:11 ` [PATCH 11/17] locking/lockdep: Adjust lockdep selftest cases Yuyang Du
2019-05-13  9:11 ` [PATCH 12/17] locking/lockdep: Remove useless lock type assignment Yuyang Du
2019-05-13  9:11 ` [PATCH 13/17] locking/lockdep: Add nest lock type Yuyang Du
2019-05-13  9:12 ` [PATCH 14/17] locking/lockdep: Support recursive read locks Yuyang Du
2019-05-13  9:12 ` [PATCH 15/17] locking/lockdep: Adjust selftest case for recursive read lock Yuyang Du
2019-05-13  9:12 ` [PATCH 16/17] locking/lockdep: Add more lockdep selftest cases Yuyang Du
2019-05-13  9:12 ` [PATCH 17/17] locking/lockdep: Remove irq-safe to irq-unsafe read check Yuyang Du
2019-05-13  9:17 ` [PATCH 00/17] Support for read-write lock deadlock detection Yuyang Du

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