On 2025-09-08, Marcos Paulo de Souza <mpdeso...@suse.com> wrote:
>> > --- a/kernel/debug/kdb/kdb_io.c
>> > +++ b/kernel/debug/kdb/kdb_io.c
>> > @@ -589,24 +589,40 @@ static void kdb_msg_write(const char *msg,
>> > int msg_len)
>> > */
>> > cookie = console_srcu_read_lock();
>> > for_each_console_srcu(c) {
>> > - if (!(console_srcu_read_flags(c) & CON_ENABLED))
>> > + struct nbcon_write_context wctxt = { };
>> > + short flags = console_srcu_read_flags(c);
>> > +
>> > + if (!console_is_usable(c, flags, true))
>> > continue;
>> > if (c == dbg_io_ops->cons)
>> > continue;
>> > - if (!c->write)
>> > - continue;
>> > - /*
>> > - * Set oops_in_progress to encourage the console
>> > drivers to
>> > - * disregard their internal spin locks: in the
>> > current calling
>> > - * context the risk of deadlock is a bigger
>> > problem than risks
>> > - * due to re-entering the console driver. We
>> > operate directly on
>> > - * oops_in_progress rather than using
>> > bust_spinlocks() because
>> > - * the calls bust_spinlocks() makes on exit are
>> > not appropriate
>> > - * for this calling context.
>> > - */
>> > - ++oops_in_progress;
>> > - c->write(c, msg, msg_len);
>> > - --oops_in_progress;
>> > +
>> > + if (flags & CON_NBCON) {
>> > + /*
>> > + * Do not continue if the console is NBCON
>> > and the context
>> > + * can't be acquired.
>> > + */
>> > + if (!nbcon_kdb_try_acquire(c, &wctxt))
>> > + continue;
>> > +
>> > + wctxt.outbuf = (char *)msg;
>> > + wctxt.len = msg_len;
>>
>> I double checked whether we initialized all members of the structure
>> correctly. And I found that we didn't. We should call here:
>>
>> nbcon_write_context_set_buf(&wctxt,
>> &pmsg.pbufs-
>> >outbuf[0],
>>
>> pmsg.outbuf_len);
Nice catch.
>> Sigh, this is easy to miss. I remember that I was not super happy
>> about this design. But the original code initialized the structure
>> on a single place...
>
> Ok, so I'll need to also export nbcon_write_context_set_buf, since it's
> currently static inside kernel/printk/nbcon.c. I'll do it for the next
> version.
How about modifying nbcon_kdb_try_acquire() to also take @msg and
@msg_len. Then, on success, @wctxt is already prepared. I do not like
the idea of external code fiddling with the fields.
John
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