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| | From bfdb34f2f26933a831684c09cadc2b782f7fbd7a Mon Sep 17 00:00:00 2001
From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Sat, 21 Oct 2017 11:33:27 -0200
Subject: [PATCH 77/90] posix: Do not use WNOHANG in waitpid call for Linux
posix_spawn
As shown in some buildbot issues on aarch64 and powerpc, calling
clone (VFORK) and waitpid (WNOHANG) does not guarantee the child
is ready to be collected. This patch changes the call back to 0
as before fe05e1cb6d64 fix.
This change can lead to the scenario 4.3 described in the commit,
where the waitpid call can hang undefinitely on the call. However
this is also a very unlikely and also undefinied situation where
both the caller is trying to terminate a pid before posix_spawn
returns and the race pid reuse is triggered. I don't see how to
correct handle this specific situation within posix_spawn.
Checked on x86_64-linux-gnu, aarch64-linux-gnu and
powerpc64-linux-gnu.
* sysdeps/unix/sysv/linux/spawni.c (__spawnix): Use 0 instead of
WNOHANG in waitpid call.
(cherry picked from commit aa95a2414e4f664ca740ad5f4a72d9145abbd426)
diff --git a/ChangeLog b/ChangeLog
index 34709f792e..c3418c3277 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
2017-11-07 Adhemerval Zanella <adhemerval.zanella@linaro.org>
+ * sysdeps/unix/sysv/linux/spawni.c (__spawnix): Use 0 instead of
+ WNOHANG in waitpid call.
+
[BZ #22273]
* sysdeps/unix/sysv/linux/spawni.c (__spawnix): Handle the case where
the auxiliary process is terminated by a signal before calling _exit
diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
index 76001b6624..7d23df84d2 100644
--- a/sysdeps/unix/sysv/linux/spawni.c
+++ b/sysdeps/unix/sysv/linux/spawni.c
@@ -374,12 +374,12 @@ __spawnix (pid_t * pid, const char *file,
ec = args.err;
if (ec > 0)
/* There still an unlikely case where the child is cancelled after
- setting args.err, due to a positive error value. Also due a
+ setting args.err, due to a positive error value. Also there is
possible pid reuse race (where the kernel allocated the same pid
- to unrelated process) we need not to undefinitely hang expecting
- an invalid pid. In both cases an error is returned to the
- caller. */
- __waitpid (new_pid, NULL, WNOHANG);
+ to an unrelated process). Unfortunately due synchronization
+ issues where the kernel might not have the process collected
+ the waitpid below can not use WNOHANG. */
+ __waitpid (new_pid, NULL, 0);
}
else
ec = -new_pid;
|