On Tue, May 19, 2020 at 05:41:47AM -0700, Joe Perches wrote:
> Except for some ancient code in drivers/scsi, this code
> may be the only kernel use of the printk return value.
Is using the printk() return value a problem?
> Code that uses the printk return value in
> kernel/locking/lockdep.c is odd because the printk
> return length includes both the length of a KERN_<LEVEL>
> prefix and the newline. depth also seems double counted.
Yeah, it seems dodgy. OTOH printk() really ought to discard the
KERN_<level> crud from the return size.
> Perhaps there's a better way to calculate this?
>
> Maybe:
> ---
> kernel/locking/lockdep.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 2fadc2635946..265227edc550 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -1960,11 +1960,9 @@ static void print_lock_class_header(struct lock_class
> *class, int depth)
>
> for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
> if (class->usage_mask & (1 << bit)) {
> - int len = depth;
> -
> - len += printk("%*s %s", depth, "", usage_str[bit]);
> - len += printk(KERN_CONT " at:\n");
> - print_lock_trace(class->usage_traces[bit], len);
> + printk("%*s %s at:\n", depth, "", usage_str[bit]);
> + print_lock_trace(class->usage_traces[bit],
> + depth + 3 + strlen(usage_str[bit]);
> }
> }
> printk("%*s }\n", depth, "");
Doesn't seem crazy...
