[klibc] [klibc:update-dash] dash: jobs - Do not block when waiting on SIGCHLD

[klibc-bot for Herbert Xu]

Commit-ID:  dfe960aa216a4495cf926fac099caacabc5684e3
Gitweb:     http://git.kernel.org/?p=libs/klibc/klibc.git;a=commit;h=dfe960aa216a4495cf926fac099caacabc5684e3
Author:     Herbert Xu <herbert at gondor.apana.org.au>
AuthorDate: Mon, 7 May 2018 00:40:34 +0800
Committer:  Ben Hutchings <ben at decadent.org.uk>
CommitDate: Sat, 28 Mar 2020 21:42:55 +0000

[klibc] dash: jobs - Do not block when waiting on SIGCHLD

[ dash commit 9e5cd41d9605e4caaac3aacdc0482f6ee220a298 ]

Because of the nature of SIGCHLD, the process may have already been
waited on and therefore we must be prepared for the case that wait
may block.  So ensure that it doesn't by using WNOHANG.

Furthermore, multiple jobs may have exited when gotsigchld is set.
Therefore we need to wait until there are no zombies left.

Lastly, waitforjob needs to be called with interrupts off and
the original patch broke that.

Fixes: 03876c0743a5 ("eval: Reap zombies after built-in...")
Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>
Signed-off-by: Ben Hutchings <ben at decadent.org.uk>

---
 usr/dash/eval.c | 12 ++++--------
 usr/dash/jobs.c | 13 ++++++++++---
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/usr/dash/eval.c b/usr/dash/eval.c
index 722066e5..13e690e7 100644
--- a/usr/dash/eval.c
+++ b/usr/dash/eval.c
@@ -859,10 +859,8 @@ bail:
 		if (!(flags & EV_EXIT) || have_traps()) {
 			INTOFF;
 			jp = makejob(cmd, 1);
-			if (forkshell(jp, cmd, FORK_FG) != 0) {
-				INTON;
+			if (forkshell(jp, cmd, FORK_FG) != 0)
 				break;
-			}
 			FORCEINTON;
 		}
 		listsetvar(varlist.list, VEXPORT|VSTACK);
@@ -875,11 +873,8 @@ bail:
 			if (execcmd && argc > 1)
 				listsetvar(varlist.list, VEXPORT);
 		}
-		if (evalbltin(cmdentry.u.cmd, argc, argv, flags)) {
-			if (exception == EXERROR && spclbltin <= 0) {
-				FORCEINTON;
-				break;
-			}
+		if (evalbltin(cmdentry.u.cmd, argc, argv, flags) &&
+		    !(exception == EXERROR && spclbltin <= 0)) {
 raise:
 			longjmp(handler->loc, 1);
 		}
@@ -892,6 +887,7 @@ raise:
 	}
 
 	status = waitforjob(jp);
+	FORCEINTON;
 
 out:
 	if (cmd->ncmd.redirect)
diff --git a/usr/dash/jobs.c b/usr/dash/jobs.c
index 3ea7e122..400628ff 100644
--- a/usr/dash/jobs.c
+++ b/usr/dash/jobs.c
@@ -974,10 +974,17 @@ waitforjob(struct job *jp)
 	int st;
 
 	TRACE(("waitforjob(%%%d) called\n", jp ? jobno(jp) : 0));
-	while ((jp && jp->state == JOBRUNNING) || gotsigchld)
-		dowait(DOWAIT_BLOCK, jp);
-	if (!jp)
+	if (!jp) {
+		int pid = gotsigchld;
+
+		while (pid > 0)
+			pid = dowait(DOWAIT_NORMAL, NULL);
+
 		return exitstatus;
+	}
+
+	while (jp->state == JOBRUNNING)
+		dowait(DOWAIT_BLOCK, jp);
 	st = getstatus(jp);
 #if JOBS
 	if (jp->jobctl) {