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[PATCH v2] 089: fix error caused by weird stdout buffer handling

To: xfs@xxxxxxxxxxx
Subject: [PATCH v2] 089: fix error caused by weird stdout buffer handling
From: Lukas Czerner <lczerner@xxxxxxxxxx>
Date: Wed, 2 Feb 2011 16:52:59 +0100
Cc: esandeen@xxxxxxxxxx, hch@xxxxxxxxxxxxx, lczerner@xxxxxxxxxx
In-reply-to: <1296660966-691-1-git-send-email-lczerner@xxxxxxxxxx>
References: <1296660966-691-1-git-send-email-lczerner@xxxxxxxxxx>
(v2: Get rid of the diff mambo-jambo in the commit description)

We have hit the error while running 089.

FSTYP         -- ext3
PLATFORM      -- Linux/x86_64 localhost 2.6.32-109.el6.x86_64

...
...
 completed 50 iterations
 completed 50 iterations
 completed 50 iterations
-completed 50 iterations
 completed 10000 iterations
 directory entries:
 t_mtab
Ran: 089
Failures: 089
Failed 1 of 1 tests

This is not very easily reproducible, however one can hit it
eventually when running 089 in the loop. The problem is apparently, that
the output might get lost, probably due to some stdio buffer weirdness.

This commit workaround the issue by adding an optional argument to the
t_mtab to specify output file. The t_mtab output is then appended to a
file which content is then printed to the stdout as it would if no
output file is used.

With this commit applied the problem is no longer reproducible.

Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
---
 089          |    9 ++++++---
 src/t_mtab.c |    8 +++++++-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/089 b/089
index e28e099..1714bec 100755
--- a/089
+++ b/089
@@ -28,6 +28,7 @@ owner=nathans@xxxxxxx
 seq=`basename $0`
 echo "QA output created by $seq"
 
+mtab_output=$TEST_DIR/mtab_output
 here=`pwd`
 tmp=/tmp/$$
 status=1       # failure is the default!
@@ -62,10 +63,12 @@ mount > t_mtab
 
 mtab()
 {
-       $here/src/t_mtab 50 &
-       $here/src/t_mtab 50 &
-       $here/src/t_mtab 50 &
+       rm -f $mtab_output
+       $here/src/t_mtab 50 $mtab_output &
+       $here/src/t_mtab 50 $mtab_output &
+       $here/src/t_mtab 50 $mtab_output &
        wait
+       cat $mtab_output
 
        $here/src/t_mtab 10000
 
diff --git a/src/t_mtab.c b/src/t_mtab.c
index 2931887..9bca954 100644
--- a/src/t_mtab.c
+++ b/src/t_mtab.c
@@ -263,6 +263,7 @@ update_mtab (void)
 int main(int argc, char **argv)
 {
        int i, stop = 100000;
+       FILE *fout = NULL;
 
        if (argc > 1)
                stop = atoi(argv[1]);
@@ -270,6 +271,11 @@ int main(int argc, char **argv)
        for (i = 0; i < stop; i++) {
                update_mtab();
        }
-       printf("completed %d iterations\n", stop);
+
+       if (argc > 2)
+               fout = fopen(argv[2],"a");
+       if (!fout)
+               fout = stdout;
+       fprintf(fout, "completed %d iterations\n", stop);
        return 0;
 }
-- 
1.7.2.3

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