From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 5D52C1A026E for ; Tue, 13 Oct 2015 14:47:15 +1100 (AEDT) In-Reply-To: <1444262666-6942-1-git-send-email-cyrilbur@gmail.com> To: Cyril Bur , linuxppc-dev@ozlabs.org From: Michael Ellerman Subject: Re: [v2] powerpc: Fix checkstop in native_hpte_clear() with lockdep Message-Id: <20151013034715.43765140FDB@ozlabs.org> Date: Tue, 13 Oct 2015 14:47:15 +1100 (AEDT) List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2015-08-10 at 00:04:26 UTC, Cyril Bur wrote: > native_hpte_clear() is called in real mode from two places: > - Early in boot during htab initialisation if firmware assisted dump is > active. > - Late in the kexec path. > > In both contexts there is no need to disable interrupts are they are > already disabled. Furthermore, locking around the tlbie() is only required > for pre POWER5 hardware. > > On POWER5 or newer hardware concurrent tlbie()s work as expected and on pre > POWER5 hardware concurrent tlbie()s could result in deadlock. This code > would only be executed at crashdump time, during which all bets are off, > concurrent tlbie()s are unlikely and taking locks is unsafe therefore the > best course of action is to simply do nothing. Concurrent tlbie()s are not > possible in the first case as secondary CPUs have not come up yet. > > Signed-off-by: Cyril Bur Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/fdf880a60835cd1dec256346 cheers