On Tue, 2006-08-15 at 13:00 -0600, Eric W. Biederman wrote: > Dave Hansen <haveblue at us.ibm.com> writes: > > > On Tue, 2006-08-15 at 12:23 -0600, Eric W. Biederman wrote: > >> +static inline pid_t pid_nr(struct pid *pid) > >> +{ > >> + pid_t nr = 0; > >> + if (pid) > >> + nr = pid->nr; > >> + return nr; > >> +} > > > > When is it valid to be passing around a NULL 'struct pid *'? > > When you don't have one at all. Look at the fcntl case a few > patches later, or even the spawnpid case. Does the fcntl() one originate from anywhere other than find_pid() in f_setown()? It seems like, perhaps, the error checking is being done at the wrong level. > Then of course there is the later chaos when we get to pid spaces > where depending on the pid namespace you are in when you call this > on a given struct pid sometimes you will get a pid value and sometimes > you won't. OK, I think it is makes sense to me to say 'get_pid(tsk, pidspace)' and get back a NULL 'struct pid' if that task isn't visible in that namespace. However, I don't get how it is handy to be able to defer the fact that the pid wasn't found until you go do a pid_nr() on that NULL. -- Dave