From d44ae88199ebf44fe721c06621a7ffc442fa34be Mon Sep 17 00:00:00 2001
From: Bernhard Voelker <mail@bernhard-voelker.de>
Date: Sun, 10 Jan 2016 01:44:04 +0100
Subject: [PATCH] tests: fix races wrt output files of background processes

At least the false positive in tail-2/follow-stdin.sh could be seen
on a 4-core i5 system with -j8.  Fix similar cases. too.

* tests/tail-2/follow-stdin.sh: Empty the 'out' file in each iteration.
Otherwise, under heavy system load, 'check_tail_output' would see the
expected output from the previous round before tail would have the
chance to come up in the background.
While at it, move the creation of the 'exp' file out of the loop.
* tests/dd/stats.sh: Empty the output file of the background process
here, too.
* tests/misc/cat-buf.sh: Likewise.
* tests/misc/stdbuf.sh: Likewise.
* tests/tail-2/wait.sh: Likewise.
---
 tests/dd/stats.sh            | 2 ++
 tests/misc/cat-buf.sh        | 1 +
 tests/misc/stdbuf.sh         | 2 ++
 tests/tail-2/follow-stdin.sh | 3 ++-
 tests/tail-2/wait.sh         | 2 +-
 5 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/tests/dd/stats.sh b/tests/dd/stats.sh
index e8bb5fa27a..182d5e7e73 100755
--- a/tests/dd/stats.sh
+++ b/tests/dd/stats.sh
@@ -38,6 +38,8 @@ cleanup_()
 }
 
 for open in '' '1'; do
+  > err || framework_failure_
+
   # Run dd with the fullblock iflag to avoid short reads
   # which can be triggered by reception of signals
   dd iflag=fullblock if=/dev/zero of=fifo count=50 bs=5000000 2>err & pid=$!
diff --git a/tests/misc/cat-buf.sh b/tests/misc/cat-buf.sh
index f12bb5bc11..a6960b566b 100755
--- a/tests/misc/cat-buf.sh
+++ b/tests/misc/cat-buf.sh
@@ -35,6 +35,7 @@ cat_buf_1()
 {
   local delay="$1"
 
+  > out || framework_failure_
   dd count=1 if=fifo > out & pid=$!
   (echo 1; sleep $delay; echo 2) | cat -v > fifo
   wait $pid
diff --git a/tests/misc/stdbuf.sh b/tests/misc/stdbuf.sh
index a5331deff8..7b9aed5036 100755
--- a/tests/misc/stdbuf.sh
+++ b/tests/misc/stdbuf.sh
@@ -66,6 +66,7 @@ stdbuf_linebuffer()
   local delay="$1"
 
   printf '1\n' > exp
+  > out || framework_failure_
   dd count=1 if=fifo > out 2> err & pid=$!
   (printf '1\n'; sleep $delay; printf '2\n') | stdbuf -oL uniq > fifo
   wait $pid
@@ -80,6 +81,7 @@ stdbuf_unbuffer()
 
   # Ensure un buffering stdout takes effect
   printf '1\n' > exp
+  > out || framework_failure_
   dd count=1 if=fifo > out 2> err & pid=$!
   (printf '1\n'; sleep $delay; printf '2\n') | stdbuf -o0 uniq > fifo
   wait $pid
diff --git a/tests/tail-2/follow-stdin.sh b/tests/tail-2/follow-stdin.sh
index 120cc3bbbc..a2f180428e 100755
--- a/tests/tail-2/follow-stdin.sh
+++ b/tests/tail-2/follow-stdin.sh
@@ -33,9 +33,10 @@ cleanup_() { kill $pid 2>/dev/null && wait $pid; }
 fastpoll='-s.1 --max-unchanged-stats=1'
 
 echo line > in || framework_failure_
+echo line > exp || framework_failure_
 
 for mode in '' '---disable-inotify'; do
-  echo line > exp || framework_failure_
+  > out || framework_failure_
 
   tail $mode -f $fastpoll < in > out 2> err & pid=$!
 
diff --git a/tests/tail-2/wait.sh b/tests/tail-2/wait.sh
index bcb04858a8..008f9f55e9 100755
--- a/tests/tail-2/wait.sh
+++ b/tests/tail-2/wait.sh
@@ -72,7 +72,7 @@ if test "$HAVE_INOTIFY"; then
   {
     local delay="$1"
 
-    touch k || framework_failure_
+    > k && > tail.out && > tail.err || framework_failure_
     tail $fastpoll -F $mode k >tail.out 2>tail.err & pid=$!
     sleep $delay
     mv k l
-- 
2.47.2