ktest: Add BISECT_TRIES to bisect test

For those cases that it takes several tries to hit a bug, it would be
useful for ktest.pl to try a test multiple times before it considers
the test as a pass. To accomplish this, BISECT_TRIES ktest config
option has been added. It is default to one, as most of the time a
bisect only needs to try a test once. But the user can now up this
to make ktest run a given test multiple times. The first failure
that is detected will set a bisect bad. It only repeats on success.

Note, as with all race bugs, there's no guarantee that if it succeeds,
it is really a good bisect. But it helps in case the bug is somewhat
reliable.

You can set BISECT_TRIES to zero, and all tests will be considered
good, unless you also set BISECT_MANUAL.

Suggested-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/tools/testing/ktest/sample.conf b/tools/testing/ktest/sample.conf
index 2eb4bd2f6ab4..172eec4517fb 100644
--- a/tools/testing/ktest/sample.conf
+++ b/tools/testing/ktest/sample.conf
@@ -1028,6 +1028,20 @@
 #   BISECT_BAD with BISECT_CHECK = good or
 #   BISECT_CHECK = bad, respectively.
 #
+# BISECT_TRIES = 5 (optional, default 1)
+#
+#   For those cases that it takes several tries to hit a bug,
+#   the BISECT_TRIES is useful. It is the number of times the
+#   test is ran before it says the kernel is good. The first failure
+#   will stop trying and mark the current SHA1 as bad.
+#
+#   Note, as with all race bugs, there's no guarantee that if
+#   it succeeds, it is really a good bisect. But it helps in case
+#   the bug is some what reliable.
+#
+#   You can set BISECT_TRIES to zero, and all tests will be considered
+#   good, unless you also set BISECT_MANUAL.
+#
 # BISECT_RET_GOOD = 0 (optional, default undefined)
 #
 #   In case the specificed test returns something other than just