[tip:locking/core] locking/lockdep: Make print_circular_bug() aware of crossrelease

[tip-bot for Byungchul Park]

Commit-ID:  383a4bc88849b804385162e81bf704f8f9690a87
Gitweb:     http://git.kernel.org/tip/383a4bc88849b804385162e81bf704f8f9690a87
Author:     Byungchul Park <byungchul.park@xxxxxxx>
AuthorDate: Mon, 7 Aug 2017 16:12:55 +0900
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 10 Aug 2017 12:29:09 +0200

locking/lockdep: Make print_circular_bug() aware of crossrelease

print_circular_bug() reporting circular bug assumes that target hlock is
owned by the current. However, in crossrelease, target hlock can be
owned by other than the current. So the report format needs to be
changed to reflect the change.

Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: akpm@xxxxxxxxxxxxxxxxxxxx
Cc: boqun.feng@xxxxxxxxx
Cc: kernel-team@xxxxxxx
Cc: kirill@xxxxxxxxxxxxx
Cc: npiggin@xxxxxxxxx
Cc: walken@xxxxxxxxxx
Cc: willy@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1502089981-21272-9-git-send-email-byungchul.park@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/locking/lockdep.c | 67 +++++++++++++++++++++++++++++++++---------------
 1 file changed, 47 insertions(+), 20 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 7f97871..1114dc4 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1139,22 +1139,41 @@ print_circular_lock_scenario(struct held_lock *src,
 		printk(KERN_CONT "\n\n");
 	}
 
-	printk(" Possible unsafe locking scenario:\n\n");
-	printk("       CPU0                    CPU1\n");
-	printk("       ----                    ----\n");
-	printk("  lock(");
-	__print_lock_name(target);
-	printk(KERN_CONT ");\n");
-	printk("                               lock(");
-	__print_lock_name(parent);
-	printk(KERN_CONT ");\n");
-	printk("                               lock(");
-	__print_lock_name(target);
-	printk(KERN_CONT ");\n");
-	printk("  lock(");
-	__print_lock_name(source);
-	printk(KERN_CONT ");\n");
-	printk("\n *** DEADLOCK ***\n\n");
+	if (cross_lock(tgt->instance)) {
+		printk(" Possible unsafe locking scenario by crosslock:\n\n");
+		printk("       CPU0                    CPU1\n");
+		printk("       ----                    ----\n");
+		printk("  lock(");
+		__print_lock_name(parent);
+		printk(KERN_CONT ");\n");
+		printk("  lock(");
+		__print_lock_name(target);
+		printk(KERN_CONT ");\n");
+		printk("                               lock(");
+		__print_lock_name(source);
+		printk(KERN_CONT ");\n");
+		printk("                               unlock(");
+		__print_lock_name(target);
+		printk(KERN_CONT ");\n");
+		printk("\n *** DEADLOCK ***\n\n");
+	} else {
+		printk(" Possible unsafe locking scenario:\n\n");
+		printk("       CPU0                    CPU1\n");
+		printk("       ----                    ----\n");
+		printk("  lock(");
+		__print_lock_name(target);
+		printk(KERN_CONT ");\n");
+		printk("                               lock(");
+		__print_lock_name(parent);
+		printk(KERN_CONT ");\n");
+		printk("                               lock(");
+		__print_lock_name(target);
+		printk(KERN_CONT ");\n");
+		printk("  lock(");
+		__print_lock_name(source);
+		printk(KERN_CONT ");\n");
+		printk("\n *** DEADLOCK ***\n\n");
+	}
 }
 
 /*
@@ -1179,7 +1198,12 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth,
 	pr_warn("%s/%d is trying to acquire lock:\n",
 		curr->comm, task_pid_nr(curr));
 	print_lock(check_src);
-	pr_warn("\nbut task is already holding lock:\n");
+
+	if (cross_lock(check_tgt->instance))
+		pr_warn("\nbut now in release context of a crosslock acquired at the following:\n");
+	else
+		pr_warn("\nbut task is already holding lock:\n");
+
 	print_lock(check_tgt);
 	pr_warn("\nwhich lock already depends on the new lock.\n\n");
 	pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
@@ -1197,7 +1221,8 @@ static inline int class_equal(struct lock_list *entry, void *data)
 static noinline int print_circular_bug(struct lock_list *this,
 				struct lock_list *target,
 				struct held_lock *check_src,
-				struct held_lock *check_tgt)
+				struct held_lock *check_tgt,
+				struct stack_trace *trace)
 {
 	struct task_struct *curr = current;
 	struct lock_list *parent;
@@ -1207,7 +1232,9 @@ static noinline int print_circular_bug(struct lock_list *this,
 	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
 		return 0;
 
-	if (!save_trace(&this->trace))
+	if (cross_lock(check_tgt->instance))
+		this->trace = *trace;
+	else if (!save_trace(&this->trace))
 		return 0;
 
 	depth = get_lock_depth(target);
@@ -1864,7 +1891,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
 	this.parent = NULL;
 	ret = check_noncircular(&this, hlock_class(prev), &target_entry);
 	if (unlikely(!ret))
-		return print_circular_bug(&this, target_entry, next, prev);
+		return print_circular_bug(&this, target_entry, next, prev, trace);
 	else if (unlikely(ret < 0))
 		return print_bfs_bug(ret);