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Date:      Thu, 9 Jul 2015 12:04:46 +0000 (UTC)
From:      Ed Schouten <ed@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r285312 - head/sys/kern
Message-ID:  <201507091204.t69C4k41009664@repo.freebsd.org>
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Author: ed
Date: Thu Jul  9 12:04:45 2015
New Revision: 285312
URL: https://svnweb.freebsd.org/changeset/base/285312

Log:
  Don't clobber td->td_retval[0] in proc_reap().
  
  While writing tests for CloudABI, I noticed that close() on process
  descriptors returns the process ID of the child process. This is
  interesting, as close() is only allowed to return 0 or -1. It turns out
  that we clobber td->td_retval[0] in proc_reap(), so that wait*()
  properly returns the process ID.
  
  Change proc_reap() to leave td->td_retval[0] alone. Set the return value
  in kern_wait6() instead, by keeping track of the PID before we
  (potentially) reap the process.
  
  Differential Revision:	https://reviews.freebsd.org/D3032
  Reviewed by:	kib

Modified:
  head/sys/kern/kern_exit.c

Modified: head/sys/kern/kern_exit.c
==============================================================================
--- head/sys/kern/kern_exit.c	Thu Jul  9 11:32:29 2015	(r285311)
+++ head/sys/kern/kern_exit.c	Thu Jul  9 12:04:45 2015	(r285312)
@@ -839,7 +839,6 @@ proc_reap(struct thread *td, struct proc
 	q = td->td_proc;
 
 	PROC_SUNLOCK(p);
-	td->td_retval[0] = p->p_pid;
 	if (status)
 		*status = p->p_xstat;	/* convert to int */
 	if (options & WNOWAIT) {
@@ -1153,6 +1152,7 @@ kern_wait6(struct thread *td, idtype_t i
     int options, struct __wrusage *wrusage, siginfo_t *siginfo)
 {
 	struct proc *p, *q;
+	pid_t pid;
 	int error, nfound, ret;
 
 	AUDIT_ARG_VALUE((int)idtype);	/* XXX - This is likely wrong! */
@@ -1191,14 +1191,17 @@ loop:
 	nfound = 0;
 	sx_xlock(&proctree_lock);
 	LIST_FOREACH(p, &q->p_children, p_sibling) {
+		pid = p->p_pid;
 		ret = proc_to_reap(td, p, idtype, id, status, options,
 		    wrusage, siginfo, 0);
 		if (ret == 0)
 			continue;
 		else if (ret == 1)
 			nfound++;
-		else
+		else {
+			td->td_retval[0] = pid;
 			return (0);
+		}
 
 		PROC_LOCK(p);
 		PROC_SLOCK(p);
@@ -1212,7 +1215,6 @@ loop:
 			if ((options & WNOWAIT) == 0)
 				p->p_flag |= P_WAITED;
 			sx_xunlock(&proctree_lock);
-			td->td_retval[0] = p->p_pid;
 
 			if (status != NULL)
 				*status = W_STOPCODE(p->p_xstat);
@@ -1231,6 +1233,7 @@ loop:
 			    p->p_pid, W_STOPCODE(p->p_xstat), p->p_xstat,
 			    p->p_xthread != NULL ? p->p_xthread->td_tid : -1);
 			PROC_UNLOCK(p);
+			td->td_retval[0] = pid;
 			return (0);
 		}
 		if ((options & WUNTRACED) != 0 &&
@@ -1241,7 +1244,6 @@ loop:
 			if ((options & WNOWAIT) == 0)
 				p->p_flag |= P_WAITED;
 			sx_xunlock(&proctree_lock);
-			td->td_retval[0] = p->p_pid;
 
 			if (status != NULL)
 				*status = W_STOPCODE(p->p_xstat);
@@ -1256,13 +1258,13 @@ loop:
 			}
 
 			PROC_UNLOCK(p);
+			td->td_retval[0] = pid;
 			return (0);
 		}
 		PROC_SUNLOCK(p);
 		if ((options & WCONTINUED) != 0 &&
 		    (p->p_flag & P_CONTINUED) != 0) {
 			sx_xunlock(&proctree_lock);
-			td->td_retval[0] = p->p_pid;
 			if ((options & WNOWAIT) == 0) {
 				p->p_flag &= ~P_CONTINUED;
 				PROC_LOCK(q);
@@ -1277,6 +1279,7 @@ loop:
 				siginfo->si_status = SIGCONT;
 				siginfo->si_code = CLD_CONTINUED;
 			}
+			td->td_retval[0] = pid;
 			return (0);
 		}
 		PROC_UNLOCK(p);

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