Commit ebfdc409 authored Aug 06, 2014 by Joe Perches Committed by Linus Torvalds Aug 06, 2014

checkpatch: attempt to find unnecessary 'out of memory' messages



Logging messages that show some type of "out of memory" error are
generally unnecessary as there is a generic message and a stack dump
done by the memory subsystem.

These messages generally increase kernel size without much added value.

Emit a warning on these types of messages.

This test looks for any inserted message function, then looks at the
previous line for an "if (!foo)" or "if (foo == NULL)" test and then
looks at the preceding statement for an allocation function like "foo =
kmalloc()"

ie: this code matches:

	foo = kmalloc();
	if (foo == NULL) {
		printk("Out of memory\n");
		return -ENOMEM;
	}

This test is very crude and incomplete.

This test can miss quite a lot of of OOM messages that do not have this
specific form.

ie: this code does not match:

	foo = kmalloc();
	if (!foo) {
		rtn = -ENOMEM;
		printk("Out of memory!\n");
		goto out;
	}

This test could also be a false positive when the logging message itself
does not specify anything about memory, but I did not find any false
positives in my limited testing.

spatch could be a better solution but correctness seems non-trivial for
that tool too.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 74e76531

scripts/checkpatch.pl

+17 −0

Original line number	Diff line number	Diff line
		@@ -4014,6 +4014,23 @@ sub process {
		}
		}

		# check for unnecessary "Out of Memory" messages
		if ($line =~ /^\+.\b$logFunctions\s\(/ &&
		$prevline =~ /^[ \+]\sif\s$\s(\!\s\|NULL\s==\s)?($Lval)(\s==\sNULL\s)?\s$/ &&
		(defined $1 \|\| defined $3) &&
		$linenr > 3) {
		my $testval = $2;
		my $testline = $lines[$linenr - 3];

		my ($s, $c) = ctx_statement_block($linenr - 3, $realcnt, 0);
		# print("line: <$line>\nprevline: <$prevline>\ns: <$s>\nc: <$c>\n\n\n");

		if ($c =~ /(?:^\|\n)[ \+]\s(?:$Type\s)?\Q$testval\E\s=\s(?:$[^$]\)\s)?\s*(?:devm_)?(?:[kv][czm]alloc(?:_node\|_array)?\b\|kstrdup\|(?:dev_)?alloc_skb)/) {
		WARN("OOM_MESSAGE",
		"Possible unnecessary 'out of memory' message\n" . $hereprev);
		}
		}

		# check for bad placement of section $InitAttribute (e.g.: __initdata)
		if ($line =~ /(\b$InitAttribute\b)/) {
		my $attr = $1;

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