checkpatch: volatile with a comment or sig_atomic_t is okay

This assumes that the comment gives some justification;
"volatile sig_atomic_t" is also self-explanatory and usually
correct.

Discussed in:
'[Qemu-devel] [PATCH] dump-guest-memory.py: fix "You can't do that without a process to debug"'

Suggested-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20171215181810.4122-1-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 34df753..3dc27d9 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2475,8 +2475,11 @@ sub process {
 
 # no volatiles please
                my $asm_volatile = qr{\b(__asm__|asm)\s+(__volatile__|volatile)\b};
-               if ($line =~ /\bvolatile\b/ && $line !~ /$asm_volatile/) {
-                       ERROR("Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt\n" . $herecurr);
+               if ($line =~ /\bvolatile\b/ && $line !~ /$asm_volatile/ &&
+                    $line !~ /sig_atomic_t/ &&
+                    !ctx_has_comment($first_line, $linenr)) {
+                       my $msg = "Use of volatile is usually wrong, please add a comment\n" . $herecurr;
+                        ERROR($msg);
                }
 
 # warn about #if 0