From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751179AbdCNIXH (ORCPT <rfc822;w@1wt.eu>);
        Tue, 14 Mar 2017 04:23:07 -0400
Received: from LGEAMRELO12.lge.com ([156.147.23.52]:33121 "EHLO
        lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751152AbdCNIXF (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 14 Mar 2017 04:23:05 -0400
X-Original-SENDERIP: 156.147.1.125
X-Original-MAILFROM: byungchul.park@lge.com
X-Original-SENDERIP: 165.244.249.26
X-Original-MAILFROM: byungchul.park@lge.com
X-Original-SENDERIP: 10.177.222.33
X-Original-MAILFROM: byungchul.park@lge.com
From: Byungchul Park <byungchul.park@lge.com>
To: <peterz@infradead.org>, <mingo@kernel.org>
CC: <tglx@linutronix.de>, <walken@google.com>, <boqun.feng@gmail.com>,
        <kirill@shutemov.name>, <linux-kernel@vger.kernel.org>,
        <linux-mm@kvack.org>, <iamjoonsoo.kim@lge.com>,
        <akpm@linux-foundation.org>, <willy@infradead.org>,
        <npiggin@gmail.com>, <kernel-team@lge.com>
Subject: [PATCH v6 04/15] lockdep: Make check_prev_add() able to handle external stack_trace
Date: Tue, 14 Mar 2017 17:18:51 +0900
Message-ID: <1489479542-27030-5-git-send-email-byungchul.park@lge.com>
X-Mailer: git-send-email 1.9.1
In-Reply-To: <1489479542-27030-1-git-send-email-byungchul.park@lge.com>
References: <1489479542-27030-1-git-send-email-byungchul.park@lge.com>
X-MIMETrack: Itemize by SMTP Server on LGEKRMHUB07/LGE/LG Group(Release 8.5.3FP6|November
 21, 2013) at 2017/03/14 17:19:43,
        Serialize by Router on LGEKRMHUB07/LGE/LG Group(Release 8.5.3FP6|November
 21, 2013) at 2017/03/14 17:19:43,
        Serialize complete at 2017/03/14 17:19:43
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Currently, a space for stack_trace is pinned in check_prev_add(), that
makes us not able to use external stack_trace. The simplest way to
achieve it is to pass an external stack_trace as an argument.

A more suitable solution is to pass a callback additionally along with
a stack_trace so that callers can decide the way to save or whether to
save. Actually crossrelease needs to do other than saving a stack_trace.
So pass a stack_trace and callback to handle it, to check_prev_add().

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
 kernel/locking/lockdep.c | 40 +++++++++++++++++++---------------------
 1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 4709110..2847356 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1797,20 +1797,13 @@ static inline void inc_chains(void)
  */
 static int
 check_prev_add(struct task_struct *curr, struct held_lock *prev,
-	       struct held_lock *next, int distance, int *stack_saved)
+	       struct held_lock *next, int distance, struct stack_trace *trace,
+	       int (*save)(struct stack_trace *trace))
 {
 	struct lock_list *entry;
 	int ret;
 	struct lock_list this;
 	struct lock_list *uninitialized_var(target_entry);
-	/*
-	 * Static variable, serialized by the graph_lock().
-	 *
-	 * We use this static variable to save the stack trace in case
-	 * we call into this function multiple times due to encountering
-	 * trylocks in the held lock stack.
-	 */
-	static struct stack_trace trace;
 
 	/*
 	 * Prove that the new <prev> -> <next> dependency would not
@@ -1858,11 +1851,8 @@ static inline void inc_chains(void)
 		}
 	}
 
-	if (!*stack_saved) {
-		if (!save_trace(&trace))
-			return 0;
-		*stack_saved = 1;
-	}
+	if (save && !save(trace))
+		return 0;
 
 	/*
 	 * Ok, all validations passed, add the new lock
@@ -1870,14 +1860,14 @@ static inline void inc_chains(void)
 	 */
 	ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
 			       &hlock_class(prev)->locks_after,
-			       next->acquire_ip, distance, &trace);
+			       next->acquire_ip, distance, trace);
 
 	if (!ret)
 		return 0;
 
 	ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
 			       &hlock_class(next)->locks_before,
-			       next->acquire_ip, distance, &trace);
+			       next->acquire_ip, distance, trace);
 	if (!ret)
 		return 0;
 
@@ -1885,8 +1875,6 @@ static inline void inc_chains(void)
 	 * Debugging printouts:
 	 */
 	if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
-		/* We drop graph lock, so another thread can overwrite trace. */
-		*stack_saved = 0;
 		graph_unlock();
 		printk("\n new dependency: ");
 		print_lock_name(hlock_class(prev));
@@ -1910,8 +1898,9 @@ static inline void inc_chains(void)
 check_prevs_add(struct task_struct *curr, struct held_lock *next)
 {
 	int depth = curr->lockdep_depth;
-	int stack_saved = 0;
 	struct held_lock *hlock;
+	struct stack_trace trace;
+	int (*save)(struct stack_trace *trace) = save_trace;
 
 	/*
 	 * Debugging checks.
@@ -1936,9 +1925,18 @@ static inline void inc_chains(void)
 		 * added:
 		 */
 		if (hlock->read != 2 && hlock->check) {
-			if (!check_prev_add(curr, hlock, next,
-						distance, &stack_saved))
+			int ret = check_prev_add(curr, hlock, next,
+						distance, &trace, save);
+			if (!ret)
 				return 0;
+
+			/*
+			 * Stop saving stack_trace if save_trace() was
+			 * called at least once:
+			 */
+			if (save && ret == 2)
+				save = NULL;
+
 			/*
 			 * Stop after the first non-trylock entry,
 			 * as non-trylock entries have added their
-- 
1.9.1