From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757836AbcJXQoa (ORCPT ); Mon, 24 Oct 2016 12:44:30 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:45640 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753766AbcJXQo3 (ORCPT ); Mon, 24 Oct 2016 12:44:29 -0400 Date: Mon, 24 Oct 2016 18:44:24 +0200 From: Peter Zijlstra To: Arnd Bergmann Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Thomas Gleixner , "H. Peter Anvin" , x86@kernel.org, Josh Poimboeuf , Borislav Petkov , Andi Kleen , linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf/x86: always warn about broken BIOS Message-ID: <20161024164424.GU3102@twins.programming.kicks-ass.net> References: <20161024152736.2635492-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20161024152736.2635492-1-arnd@arndb.de> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 24, 2016 at 05:26:37PM +0200, Arnd Bergmann wrote: > The intialization function checks for various failure scenarios, but > unfortunately the compiler gets a little confused about the possible > combinations, leading to a false-positive build warning when > -Wmaybe-uninitialized is set: > > arch/x86/events/core.c: In function ‘init_hw_perf_events’: > arch/x86/events/core.c:264:3: warning: ‘reg_fail’ may be used uninitialized in this function [-Wmaybe-uninitialized] > arch/x86/events/core.c:264:3: warning: ‘val_fail’ may be used uninitialized in this function [-Wmaybe-uninitialized] > pr_err(FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is %Lx)\n", > > It seems reasonable to move the check for the broken BIOS a little > higher in the function, which will lead to the kernel warning about > both the BIOS and and broken hardware if both are faulty, but it > has no effect otherwise at runtime. > > Moving it ahead of the check for broken hardware however gets rid > of the compile-time warning. > > Signed-off-by: Arnd Bergmann Wouldn't something simple like this not be, well, simpler? --- arch/x86/events/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index d31735f37ed7..3bc4d76ce0bb 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -190,8 +190,8 @@ static void release_pmc_hardware(void) {} static bool check_hw_exists(void) { - u64 val, val_fail, val_new= ~0; - int i, reg, reg_fail, ret = 0; + u64 val, val_fail = 0, val_new= ~0; + int i, reg, reg_fail = 0, ret = 0; int bios_fail = 0; int reg_safe = -1;