Date: Mon, 31 Mar 2008 23:03:31 -0700 From: "Rao, Nikhil" <nikhil.rao@intel.com> To: <freebsd-hackers@freebsd.org> Subject: pfind() and the proc structure Message-ID: <12A5C15467D5B94F8E0FF265D9498ADD02CBF8FF@orsmsx419.amr.corp.intel.com> In-Reply-To: <20080329120018.0A8F5106567F@hub.freebsd.org> References: <20080329120018.0A8F5106567F@hub.freebsd.org>
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Hi List, The pfind(..) (in kern_proc.c) function below returns the proc structure for the PID passed in 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. Thanks, 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 }
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