On Tue, 2020-05-19 at 16:45 +0200, Peter Zijlstra wrote: > 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?
Maybe. The printk code isn't obviously correct. https://lore.kernel.org/lkml/[email protected]/ > > 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. Or change it to the actual output of '<' level '>' instead of the internal KERN_SOH level. > > 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...
