[PATCH v3 4/8] lockdep: Add a kernel parameter, crossrelease_fullstack

Byungchul Park
2017-10-24T09:41:53Z

Make whether to allow recording full stack, in cross-release feature,
switchable at boot time via a kernel parameter, 'crossrelease_fullstack'.
In case of a splat with no stack trace, one could just reboot and set
the kernel parameter to get the full data without having to recompile
the kernel.

Change CONFIG_CROSSRELEASE_STACK_TRACE default from N to Y, and
introduce the new kernel parameter.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
Documentation/admin-guide/kernel-parameters.txt | 3 +++
kernel/locking/lockdep.c | 18 ++++++++++++++++--
lib/Kconfig.debug | 5 +++--
3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ead7f40..4107b01 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -709,6 +709,9 @@
It will be ignored when crashkernel=X,high is not used
or memory reserved is below 4G.

+ crossrelease_fullstack
+ [KNL] Allow to record full stack trace in cross-release
+
cryptomgr.notests
[KNL] Disable crypto self-tests

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 5c2ddf2..feba887 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -76,6 +76,15 @@
#define lock_stat 0
#endif

+static int crossrelease_fullstack;
+static int __init allow_crossrelease_fullstack(char *str)
+{
+ crossrelease_fullstack = 1;
+ return 0;
+}
+
+early_param("crossrelease_fullstack", allow_crossrelease_fullstack);
+
/*
* lockdep_lock: protects the lockdep graph, the hashes and the
* class/list/hash allocators.
@@ -4864,8 +4873,13 @@ static void add_xhlock(struct held_lock *hlock)
xhlock->trace.max_entries = MAX_XHLOCK_TRACE_ENTRIES;
xhlock->trace.entries = xhlock->trace_entries;
#ifdef CONFIG_CROSSRELEASE_STACK_TRACE
- xhlock->trace.skip = 3;
- save_stack_trace(&xhlock->trace);
+ if (crossrelease_fullstack) {
+ xhlock->trace.skip = 3;
+ save_stack_trace(&xhlock->trace);
+ } else {
+ xhlock->trace.nr_entries = 1;
+ xhlock->trace.entries[0] = hlock->acquire_ip;
+ }
#else
xhlock->trace.nr_entries = 1;
xhlock->trace.entries[0] = hlock->acquire_ip;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index fe8fceb..132536d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1228,7 +1228,7 @@ config LOCKDEP_COMPLETIONS
config CROSSRELEASE_STACK_TRACE
bool "Record more than one entity of stack trace in crossrelease"
depends on LOCKDEP_CROSSRELEASE
- default n
+ default y
help
The lockdep "cross-release" feature needs to record stack traces
(of calling functions) for all acquisitions, for eventual later
@@ -1238,7 +1238,8 @@ config CROSSRELEASE_STACK_TRACE
full analysis. This option turns on the saving of the full stack
trace entries.

- If unsure, say N.
+ To make the feature actually on, set "crossrelease_fullstack"
+ kernel parameter, too.

config DEBUG_LOCKDEP
bool "Lock dependency engine debugging"
--
1.9.1