From aa95a2414e4f664ca740ad5f4a72d9145abbd426 Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Sat, 21 Oct 2017 11:33:27 -0200 Subject: 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. --- ChangeLog | 5 +++++ sysdeps/unix/sysv/linux/spawni.c | 10 +++++----- 2 files changed, 10 insertions(+), 5 deletions(-) diff --git a/ChangeLog b/ChangeLog index b756f97aa4..4448c3d791 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +2017-10-23 Adhemerval Zanella + + * sysdeps/unix/sysv/linux/spawni.c (__spawnix): Use 0 instead of + WNOHANG in waitpid call. + 2017-10-23 Siddhesh Poyarekar * manual/conf.texi (_SC_LEVEL1_DCACHE_LINESIZE, diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c index d15fbb1eca..fb83c2ed53 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; -- cgit 1.4.1