Re: [lwip-users] Debug code

[Marc Boucher]

On Sun, Mar 09, 2003 at 02:34:54AM +0100, Leon Woestenberg wrote:
> 
> ----- Original Message -----
> From: "Marc Boucher" <address@hidden>
> 
> > > DEBUGF(SOCKETS_DEBUG, (" port=%u)\n", ntohs(local_port)));
> > >#endif
> >
> > Btw such debug contructs are also very problematic on systems where
> multiple
> > tasks simultaneously generate debug output, since other messages can end
> up
> > being inserted between the multiple print calls resulting in mixed /
> > confusing lines.
> >
> > Better would be to print everything at once using a
> > "lwip_bind(%d, addr=%s port=%u)\n" format string with some
> inet_addr()-like
> > function (minus re-entrancy issues) or macro/token to handle IP address
> > formatting.
> >
> This is not generally true. If the OS can switch tasks pre-emptively, and
> printf does not
> lock the scheduler, the printf()ing task can simply be switched from the CPU
> and a new
> printf()ing task can be switched in.
> 
> I have solved this by having DEBUGF lock the scheduler, call printf(),
> unlock the scheduler.
> 
> Leon.

My point was that using multiple DEBUGF / ip_addr_debug_print / printf calls
to generate a single line of output is problematic on systems where
other tasks can generate output at the same time. Adding locking to
protect each call doesn't solve this problem.

Marc