From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37609) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fImnH-0005yg-9d for qemu-devel@nongnu.org; Tue, 15 May 2018 23:08:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fImnE-0007WK-3w for qemu-devel@nongnu.org; Tue, 15 May 2018 23:07:59 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:49080 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fImnD-0007Vy-Vi for qemu-devel@nongnu.org; Tue, 15 May 2018 23:07:56 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 67D097C6B1 for ; Wed, 16 May 2018 03:07:55 +0000 (UTC) Date: Wed, 16 May 2018 11:07:50 +0800 From: Peter Xu Message-ID: <20180516030750.GC9089@xz-mi> References: <20180515091356.24106-1-peterx@redhat.com> <584bbd99-11dd-8da9-a5b4-de285cebc84d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <584bbd99-11dd-8da9-a5b4-de285cebc84d@redhat.com> Subject: Re: [Qemu-devel] [PATCH RFC] qemu-error: introduce error_report_once List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org, Markus Armbruster On Tue, May 15, 2018 at 10:29:39AM -0500, Eric Blake wrote: > On 05/15/2018 04:13 AM, Peter Xu wrote: > > I stole the printk_once() macro. > > > > I always wanted to be able to print some error directly if there is a > > buffer to dump, however we can't use error_report() really quite often > > when there can be any DDOS attack. To avoid that, we can introduce a > > print-once function for it. > > > > CC: Markus Armbruster > > Signed-off-by: Peter Xu > > --- > > We can for sure introduce similar functions for the rest of the > > error_*() functions, it's just an idea to see whether we'd like it > > in general. > > --- > > include/qemu/error-report.h | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h > > index e1c8ae1a52..efebb80e2c 100644 > > --- a/include/qemu/error-report.h > > +++ b/include/qemu/error-report.h > > @@ -44,6 +44,18 @@ void error_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); > > void warn_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); > > void info_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); > > +#define error_report_once(fmt, ...) \ > > + ({ \ > > + static bool __print_once; \ > > Double-underscore names are reserved for the compiler's use, not ours. > Better would be naming this: > > static bool print_once_; > > with a trailing underscore, or at most a single leading underscore. > > > + bool __ret_print_once = !__print_once; \ > > Same comment for this variable. Sure! (I am wondering why Linux is always using that way to name lots of variables, and I'm surprised that I got 385350 after I run this under the Linux repo: 'git grep "__[a-z][a-z]" | wc -l', even considering some false positives) Thanks, -- Peter Xu