When kernel oops happens, lock debugging is turned off by debug_locks_off()
in oops_enter() via calling __debug_locks_off() which set debug_locks to 0
via xchg(). But, calling to __debug_locks_off() to check lock debugging state
in add_taint() called by oops_end() will always return false since xchg()
returns the old value of debug_locks which is cleared in oops_enter() already.
This prevents add_taint() from printing out lock debugging disable information
although LOCKDEP_NOW_UNRELIABLE is passed to it.
Check lock debugging state via !debug_locks to fix this. Although
!__debug_locks_off() could do the same thing, it may look confusing.
Before the fix, oops output looks like:
RIP [<ffffffff8119d2f8>] release_freepages+0x18/0xa0
RSP <ffff88036173fcf8>
CR2: 0000000000000000
[ end trace 2e96d09e0ba6342f ]
Aftere the fix, it looks like:
RIP [<ffffffff8119d2f8>] release_freepages+0x18/0xa0
RSP <ffff88036173fcf8>
CR2: 0000000000000000
Disabling lock debugging due to kernel taint
[ end trace 2e96d09e0ba6342f ]
And, fix a trivial typo in the comment of add_taint().
Signed-off-by: Yang Shi <yang....@linaro.org>
---
kernel/panic.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/panic.c b/kernel/panic.c
index 535c965..859499d 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -346,11 +346,11 @@ unsigned long get_taint(void)
* @lockdep_ok: whether lock debugging is still OK.
*
* If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
- * some notewortht-but-not-corrupting cases, it can be set to true.
+ * some noteworthy-but-not-corrupting cases, it can be set to true.
*/
void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
{
- if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
+ if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && !debug_locks)
pr_warn("Disabling lock debugging due to kernel taint\n");
set_bit(flag, &tainted_mask);
--
2.0.2
