[PATCH 5/8] ktest/config_bisect: Simplify bisect logic

[Scott Wood]

From: Scott Wood <oss@xxxxxxxxxxxx>

There's no need to diff the configs three different ways or to do things
like "first lets enable things in bad config that are enabled in good
config".  If "undefined" is treated as just another value that a config
can have, then all the cases reduce to "a problem with a difference in
values".

Plus, the old logic would fail with some inputs, as it confuses a symbol
not appearing in the .config file (and thus in the hash) with a symbol
not being selected (and thus being present in the hash with a value of "#
CONFIG_FOO is not set").  diff_configs checks for the former, but
assuming the input configs have been run through make oldconfig, any
symbols that are not present at all are not selectable and thus are side
effects of some other difference -- not relevant to the bisection.

If the bisection proceeds to the point where there are none of these
side effects left, len_b and len_g will both be zero.  If len_diff is
greater than one at this point, a new config to try will not be produced.

Since b_arr and g_arr are irrelevant to the bisection, remove them and
only calculate differences in symbols that are present in both hashes, and
proceed directly to the logic that deals with differences in value.

While we're at it, have diff_config_vals return an array of keys rather
than a hash, since the keys are the only thing ever looked at.

Signed-off-by: Scott Wood <swood@xxxxxxxxxx>
---
 tools/testing/ktest/config-bisect.pl | 108 ++++++++---------------------------
 1 file changed, 23 insertions(+), 85 deletions(-)

diff --git a/tools/testing/ktest/config-bisect.pl b/tools/testing/ktest/config-bisect.pl
index 1768d145ced8..63a3a940b5de 100755
--- a/tools/testing/ktest/config-bisect.pl
+++ b/tools/testing/ktest/config-bisect.pl
@@ -60,7 +60,6 @@ sub save_config {
 }
 
 # compare two config hashes, and return configs with different vals.
-# It returns B's config values, but you can use A to see what A was.
 sub diff_config_vals {
 	my ($pa, $pb) = @_;
 
@@ -68,34 +67,15 @@ sub diff_config_vals {
 	my %a = %{$pa};
 	my %b = %{$pb};
 
-	my %ret;
+	my @ret;
 
 	foreach my $item (keys %a) {
 		if (defined($b{$item}) && $b{$item} ne $a{$item}) {
-			$ret{$item} = $b{$item};
+			push @ret, $item;
 		}
 	}
 
-	return %ret;
-}
-
-# compare two config hashes and return the configs in B but not A
-sub diff_configs {
-	my ($pa, $pb) = @_;
-
-	my %ret;
-
-	# crappy Perl way to pass in hashes.
-	my %a = %{$pa};
-	my %b = %{$pb};
-
-	foreach my $item (keys %b) {
-		if (!defined($a{$item})) {
-			$ret{$item} = $b{$item};
-		}
-	}
-
-	return %ret;
+	return @ret;
 }
 
 # return if two configs are equal or not
@@ -170,89 +150,47 @@ sub run_config_bisect {
 	my %good_configs = %{$pgood};
 	my %bad_configs = %{$pbad};
 
-	my %diff_configs = diff_config_vals \%good_configs, \%bad_configs;
-	my %b_configs = diff_configs \%good_configs, \%bad_configs;
-	my %g_configs = diff_configs \%bad_configs, \%good_configs;
-
-	my @diff_arr = keys %diff_configs;
+	my @diff_arr = diff_config_vals \%good_configs, \%bad_configs;
 	my $len_diff = $#diff_arr + 1;
 
-	my @b_arr = keys %b_configs;
-	my $len_b = $#b_arr + 1;
-
-	my @g_arr = keys %g_configs;
-	my $len_g = $#g_arr + 1;
-
 	my $runtest = 1;
 	my %new_configs;
 	my $ret;
 
-	# First, lets get it down to a single subset.
-	# Is the problem with a difference in values?
-	# Is the problem with a missing config?
-	# Is the problem with a config that breaks things?
-
-	# Enable all of one set and see if we get a new bad
-	# or good config.
-
-	# first set the good config to the bad values.
-
-	print "d=$len_diff g=$len_g b=$len_b\n";
+	print "d=$len_diff\n";
 
-	# first lets enable things in bad config that are enabled in good config
+	if ($len_diff <= 1) {
+		print "$0: No more bisecting possible\n";
+		exit 2;
+	}
 
-	if ($len_diff > 0) {
-		if ($len_b > 0 || $len_g > 0) {
-			my %tmp_config = %bad_configs;
+	my %tmp_config = %bad_configs;
 
-			print "Set tmp config to be bad config with good config values\n";
-			foreach my $item (@diff_arr) {
-				$tmp_config{$item} = $good_configs{$item};
-			}
+	my $half = int($#diff_arr / 2);
+	my @tophalf = @diff_arr[0 .. $half];
 
-			$runtest = process_new_config \%tmp_config,
-				\%new_configs, \%good_configs,
-				\%bad_configs, $outfile;
-		}
+	print "Settings bisect with top half:\n";
+	foreach my $item (@tophalf) {
+		$tmp_config{$item} = $good_configs{$item};
 	}
 
-	if (!$runtest && $len_diff > 0) {
+	$runtest = process_new_config \%tmp_config, \%new_configs,
+		\%good_configs, \%bad_configs, $outfile;
 
-		if ($len_diff == 1) {
-			process_failed $diff_arr[0];
-			return 1;
-		}
+	if (!$runtest) {
 		my %tmp_config = %bad_configs;
 
-		my $half = int($#diff_arr / 2);
-		my @tophalf = @diff_arr[0 .. $half];
+		print "Try bottom half\n";
 
-		print "Settings bisect with top half:\n";
-		print "Set tmp config to be bad config with some good config values\n";
-		foreach my $item (@tophalf) {
+		my @bottomhalf = @diff_arr[$half+1 .. $#diff_arr];
+
+		foreach my $item (@bottomhalf) {
 			$tmp_config{$item} = $good_configs{$item};
 		}
 
 		$runtest = process_new_config \%tmp_config, \%new_configs,
-			\%good_configs, \%bad_configs, $outfile;
-
-		if (!$runtest) {
-			my %tmp_config = %bad_configs;
-
-			print "Try bottom half\n";
-
-			my @bottomhalf = @diff_arr[$half+1 .. $#diff_arr];
-
-			foreach my $item (@bottomhalf) {
-				$tmp_config{$item} = $good_configs{$item};
-			}
-
-			$runtest = process_new_config \%tmp_config,
-				\%new_configs, \%good_configs,
-				\%bad_configs, $outfile;
-		}
+				\%good_configs, \%bad_configs, $outfile;
 	}
-
 }
 
 sub cb_by_file {
-- 
2.9.4