From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935230AbdJJUOB (ORCPT ); Tue, 10 Oct 2017 16:14:01 -0400 Received: from mga06.intel.com ([134.134.136.31]:53569 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933881AbdJJUN7 (ORCPT ); Tue, 10 Oct 2017 16:13:59 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,359,1503385200"; d="scan'208";a="1180653689" From: Andi Kleen To: "Luck\, Tony" Cc: Borislav Petkov , Jeremy Cline , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org, Laura Abbott Subject: Re: x86/mce: suspicious RCU usage in 4.13.4 References: <9840bf0d-6756-75eb-1a2d-d3aace235244@redhat.com> <20171010194426.s7keveirclglx6vh@pd.tnic> <20171010200841.uhniuwc7pulqgmic@intel.com> Date: Tue, 10 Oct 2017 13:13:58 -0700 In-Reply-To: <20171010200841.uhniuwc7pulqgmic@intel.com> (Tony Luck's message of "Tue, 10 Oct 2017 13:08:41 -0700") Message-ID: <871smasqux.fsf@linux.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Luck, Tony" writes: >> for (;;) { >> entry = mce_log_get_idx_check(mcelog.next); > > Can't this get even simpler? Do we need the loop? The mutex > will now protect us while we check to see if there is a slot > to stash this new entry. Also just say: IMHO the warning is just bogus. There's nothing here that actually uses RCU. I would just remove it. >> if (entry >= MCE_LOG_LEN) { >> - set_bit(MCE_OVERFLOW, >> - (unsigned long *)&mcelog.flags); >> + set_bit(MCE_OVERFLOW, (unsigned long *)&mcelog.flags); > > Need to mutex_unlock(&mce_chrdev_read_mutex); here. And yes that too. -Andi From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: x86/mce: suspicious RCU usage in 4.13.4 From: Andi Kleen Message-Id: <871smasqux.fsf@linux.intel.com> Date: Tue, 10 Oct 2017 13:13:58 -0700 To: "Luck, Tony" Cc: Borislav Petkov , Jeremy Cline , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org, Laura Abbott List-ID: Ikx1Y2ssIFRvbnkiIDx0b255Lmx1Y2tAaW50ZWwuY29tPiB3cml0ZXM6Cgo+PiAgCWZvciAoOzsp IHsKPj4gIAkJZW50cnkgPSBtY2VfbG9nX2dldF9pZHhfY2hlY2sobWNlbG9nLm5leHQpOwo+Cj4g Q2FuJ3QgdGhpcyBnZXQgZXZlbiBzaW1wbGVyPyBEbyB3ZSBuZWVkIHRoZSBsb29wPyBUaGUgbXV0 ZXgKPiB3aWxsIG5vdyBwcm90ZWN0IHVzIHdoaWxlIHdlIGNoZWNrIHRvIHNlZSBpZiB0aGVyZSBp cyBhIHNsb3QKPiB0byBzdGFzaCB0aGlzIG5ldyBlbnRyeS4gQWxzbyBqdXN0IHNheToKCklNSE8g dGhlIHdhcm5pbmcgaXMganVzdCBib2d1cy4gVGhlcmUncyBub3RoaW5nIGhlcmUgdGhhdCBhY3R1 YWxseQp1c2VzIFJDVS4gSSB3b3VsZCBqdXN0IHJlbW92ZSBpdC4KCj4+ICAJCQlpZiAoZW50cnkg Pj0gTUNFX0xPR19MRU4pIHsKPj4gLQkJCQlzZXRfYml0KE1DRV9PVkVSRkxPVywKPj4gLQkJCQkJ KHVuc2lnbmVkIGxvbmcgKikmbWNlbG9nLmZsYWdzKTsKPj4gKwkJCQlzZXRfYml0KE1DRV9PVkVS RkxPVywgKHVuc2lnbmVkIGxvbmcgKikmbWNlbG9nLmZsYWdzKTsKPgo+IE5lZWQgdG8gbXV0ZXhf dW5sb2NrKCZtY2VfY2hyZGV2X3JlYWRfbXV0ZXgpOyBoZXJlLgoKQW5kIHllcyB0aGF0IHRvby4K Ci1BbmRpCi0tLQpUbyB1bnN1YnNjcmliZSBmcm9tIHRoaXMgbGlzdDogc2VuZCB0aGUgbGluZSAi dW5zdWJzY3JpYmUgbGludXgtZWRhYyIgaW4KdGhlIGJvZHkgb2YgYSBtZXNzYWdlIHRvIG1ham9y ZG9tb0B2Z2VyLmtlcm5lbC5vcmcKTW9yZSBtYWpvcmRvbW8gaW5mbyBhdCAgaHR0cDovL3ZnZXIu a2VybmVsLm9yZy9tYWpvcmRvbW8taW5mby5odG1sCg==