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.shi@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);