[tip:locking/core] locking/lockdep: Introduce CONFIG_BOOTPARAM_LOCKDEP_CROSSRELEASE_FULLSTACK=y

[tip-bot for Byungchul Park]

Commit-ID:  e121d64e16484d4a5eba94cd2fa9eb3848b7c9c2
Gitweb:     https://git.kernel.org/tip/e121d64e16484d4a5eba94cd2fa9eb3848b7c9c2
Author:     Byungchul Park <byungchul.park@xxxxxxx>
AuthorDate: Wed, 25 Oct 2017 17:56:02 +0900
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 25 Oct 2017 12:19:02 +0200

locking/lockdep: Introduce CONFIG_BOOTPARAM_LOCKDEP_CROSSRELEASE_FULLSTACK=y

Add a Kconfig knob that enables the lockdep "crossrelease_fullstack" boot parameter.

Suggested-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: amir73il@xxxxxxxxx
Cc: axboe@xxxxxxxxx
Cc: darrick.wong@xxxxxxxxxx
Cc: david@xxxxxxxxxxxxx
Cc: hch@xxxxxxxxxxxxx
Cc: idryomov@xxxxxxxxx
Cc: johan@xxxxxxxxxx
Cc: johannes.berg@xxxxxxxxx
Cc: kernel-team@xxxxxxx
Cc: linux-block@xxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-xfs@xxxxxxxxxxxxxxx
Cc: oleg@xxxxxxxxxx
Cc: tj@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1508921765-15396-7-git-send-email-byungchul.park@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/locking/lockdep.c |  4 ++++
 lib/Kconfig.debug        | 15 +++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 160b5d6..db933d0 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -76,7 +76,11 @@ module_param(lock_stat, int, 0644);
 #define lock_stat 0
 #endif
 
+#ifdef CONFIG_BOOTPARAM_LOCKDEP_CROSSRELEASE_FULLSTACK
+static int crossrelease_fullstack = 1;
+#else
 static int crossrelease_fullstack;
+#endif
 static int __init allow_crossrelease_fullstack(char *str)
 {
 	crossrelease_fullstack = 1;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c1e720a..2b439a5 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1179,6 +1179,21 @@ config LOCKDEP_COMPLETIONS
 	 A deadlock caused by wait_for_completion() and complete() can be
 	 detected by lockdep using crossrelease feature.
 
+config BOOTPARAM_LOCKDEP_CROSSRELEASE_FULLSTACK
+	bool "Enable the boot parameter, crossrelease_fullstack"
+	depends on LOCKDEP_CROSSRELEASE
+	default n
+	help
+	 The lockdep "cross-release" feature needs to record stack traces
+	 (of calling functions) for all acquisitions, for eventual later
+	 use during analysis. By default only a single caller is recorded,
+	 because the unwind operation can be very expensive with deeper
+	 stack chains.
+
+	 However a boot parameter, crossrelease_fullstack, was
+	 introduced since sometimes deeper traces are required for full
+	 analysis. This option turns on the boot parameter.
+
 config DEBUG_LOCKDEP
 	bool "Lock dependency engine debugging"
 	depends on DEBUG_KERNEL && LOCKDEP