From 16bc83afa8de707e4119b178758437415857518e Mon Sep 17 00:00:00 2001 From: Amitay Isaacs Date: Tue, 9 Apr 2019 14:44:04 +1000 Subject: [PATCH] ctdb-common: Avoid race between fd and signal events BUG: https://bugzilla.samba.org/show_bug.cgi?id=13895 In run_proc, there was an implicit assumption that when a process exits, fd event (pipe between parent and child) would be processed first and signal event (SIGCHLD for the child) would be processed later. However, that is not the case. SIGCHLD can be received asynchronously any time even when the pipe data has not fully been read. This causes run_proc to miss some of the output from child process in tests. When SIGCHLD is being processed, if the pipe between parent and child is still open, then do an explict read from the pipe to ensure we read any data still in the pipe before closing the pipe. Signed-off-by: Amitay Isaacs Reviewed-by: Martin Schwenke Autobuild-User(master): Amitay Isaacs Autobuild-Date(master): Fri Apr 12 08:19:29 UTC 2019 on sn-devel-144 (cherry picked from commit 289201277cd983b27cdfd5376c607eab112b4082) --- ctdb/common/run_proc.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/ctdb/common/run_proc.c b/ctdb/common/run_proc.c index 97895b383b9..037b6d9651d 100644 --- a/ctdb/common/run_proc.c +++ b/ctdb/common/run_proc.c @@ -295,6 +295,13 @@ again: proc->result.sig = WTERMSIG(status); } + /* Confirm that all data has been read from the pipe */ + if (proc->fd != -1) { + proc_read_handler(ev, proc->fde, 0, proc); + TALLOC_FREE(proc->fde); + proc->fd = -1; + } + /* Active run_proc request */ if (proc->req != NULL) { run_proc_done(proc->req); -- 2.20.1