Hello David,
> Might be useful, for example, with ps ... parse_pid => strtonum might
> use pid_max as legit upper limit, ... top ... etc etc ...
Using pid_max to validate if a given number is a valid pid would yield
false negatives; there might be a process with a higher pid still
running _after_ pid_max has been set to a lower value via sysctl.
> diff --git a/sys/sys/proc.h b/sys/sys/proc.h
> index 335bc14..7192dad 100644
> --- a/sys/sys/proc.h
> +++ b/sys/sys/proc.h
> @@ -407,6 +407,12 @@ struct uidinfo *uid_find(uid_t);
> #define PID_MAX 32766
> #define NO_PID (PID_MAX+1)
>
> +/*
> + * Boundaries of sysctl possible values for pid_max
> + */
> +#define PID_SYSCTL_LW 1024
I think this value is far to low. Even with just a bunch of processes
you will have pid collisions in allocpid(), causing forking to take
longer. Also with the pid space getting smaller you make the pids
essentialy guessable, which counteracts the idea of pid randomization.
> +#define PID_SYSCTL_UP 102400
Why choose this particular value? If i remember correctly the underlying
type of pid_t is int32_t. What is the reason to not use 2^31 (-2) as the
upper bound?
> +
> #define SESS_LEADER(pr) ((pr)->ps_session->s_leader == (pr))
> #define SESSHOLD(s) ((s)->s_count++)
> #define SESSRELE(s) do {
> \
I agree with Owain, that changing PID_MAX, if it is necessary, should be
done globally and not with a sysctl. Do you have any evidence showing
that the pid space is too small?
cheers,
natano
