RE: pfind() and the proc structure

Ok, I should have caught that :-( Another question -=20
Now that the PROC_LOCK on p is obtained the all_proc lock is released
and the function returns, at this point can't the proc get deallocated ?

Nikhil

242 struct proc *
243 pfind(pid)
244         register pid_t pid;
245 {
246         register struct proc *p;
247=20
248         sx_slock(&allproc_lock);
249         LIST_FOREACH(p, PIDHASH(pid), p_hash)
250                 if (p->p_pid =3D=3D pid) {
251                         if (p->p_state =3D=3D PRS_NEW) {
252                                 p =3D NULL;
253                                 break;
254                         }
255                         PROC_LOCK(p);
256                         break;
257                 }
258         sx_sunlock(&allproc_lock);
259         return (p);
260 }

-----Original Message-----
From: Roman Divacky [mailto:[e-mail]]=20
Sent: Tuesday, April 01, 2008 12:56 AM
To: Rao, Nikhil
Cc: [e-mail]
Subject: Re: pfind() and the proc structure

On Mon, Mar 31, 2008 at 11:03:31PM -0700, Rao, Nikhil wrote:
> Hi List,
>=20
> The pfind(..) (in kern_proc.c) function below returns the proc
structure
> for the PID passed in
>=20
> Say the thread that calls pfind() gets blocked at PROC_LOCK(p) (line
255
> below), in the meantime what prevents the process from exiting and
> deallocating the proc structure ? Maybe I am missing something simple
or
> the answer requires knowledge of the mutex implementation.

thats what the allproc_lock is there for
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