From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751309AbdAWQwN (ORCPT ); Mon, 23 Jan 2017 11:52:13 -0500 Received: from mout.kundenserver.de ([212.227.126.134]:63796 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750713AbdAWQwK (ORCPT ); Mon, 23 Jan 2017 11:52:10 -0500 From: Arnd Bergmann To: Andrew Morton Cc: Arnd Bergmann , Dan Williams , Yasuaki Ishimatsu , Fabian Frederick , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] mm: fix maybe-uninitialized warning in section_deactivate() Date: Mon, 23 Jan 2017 17:51:17 +0100 Message-Id: <20170123165156.854464-1-arnd@arndb.de> X-Mailer: git-send-email 2.9.0 X-Provags-ID: V03:K0:/O8JCzYlUUVMX21NGwllpKwH8q98w6SaHix1rsW2VFWfT6Bvj5V Eps46Tdq26bKgHOhJ0smnqdZZTV2/zp8BKLpSWhsPCmXDKzCgogSFdF12gIKqMryyCsk74E vU9+AfStYg7rXYLfSwVu7g80jP9Ts2aDPFdze9A4QcNDEZggwhlnx0c5zXyPexnnEY2InB6 XZgYrNcf88s84YKHh+/VA== X-UI-Out-Filterresults: notjunk:1;V01:K0:s1EYFsO+4SU=:hxQtHJLlpMqFjHfrSM1IDE DrkMfFWD2f6rWElT+YLVWyLtVpmThsQxJUuzZyDFLambH3jVFYb+FI1/R4eBxk6XEK/GmM72W G9Hpfd7Olig/N7x54GKF7G60YU+CgxfZGb6DPjg861wEW+hKv+4y307Ec9t3+oKqbpmBe8h6q rbI7uDmV96yTQS/kMqq4n8+C6J0j11w4t5tZzdKqD14KNe1sQpCAhff+nOaWbgjtqJ2/wHd6C n5YqW1dBhDtwxgy23KR+Ko+bSNkJD5/lqPN0XcKrYFK735yv8sdWWjVfdLv+LZgjAwAKgHDkh yKGvx4S64pX1RjhKFqsX+cQt2R6Mf/o25lGPKv2rjyVOFoeRLrX466aahoBNd9NEDa7qUoaOY X219GeBirFddvLcDDmNrW2e55kHdFdy1x3Fn3S2gJCYK7VpkakzbajT+5EObTxVfEHmSy55jD C6dmTcuKoimt7llunjltfhmlkViN8SdZlK1zFWeGRDZrenoZ7DIl9wSlGY6l/LsqOZdJxDfnF IfXnACGYcDAJ8kFm9P3nnEHC+MRXj3FVtnEMs7mGHIjF93UFYC2NRAvRJalev6OP4slKlBnJl h1Y260yx66CYk5VC8HoJTe++CiWZA02H+R1Obvj5O8MV5qBq2hqTQl5JuDH2FscGnM5YIIJpu N7IX5tyZBGPwpRl7gzRGL8B/0lgI1SGFXgdEZMUcBUQaXOvz1NKF2yvKYgILt6qfYW+U= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org gcc cannot track the combined state of the 'mask' variable across the barrier in pgdat_resize_unlock() at compile time, so it warns that we can run into undefined behavior: mm/sparse.c: In function 'section_deactivate': mm/sparse.c:802:7: error: 'early_section' may be used uninitialized in this function [-Werror=maybe-uninitialized] We know that this can't happen because the spin_unlock() doesn't affect the mask variable, so this is a false-postive warning, but rearranging the code to bail out earlier here makes it obvious to the compiler as well. Fixes: mmotm ("mm: support section-unaligned ZONE_DEVICE memory ranges") Signed-off-by: Arnd Bergmann --- mm/sparse.c | 33 +++++++++++++++++---------------- 1 file changed, 17 insertions(+), 16 deletions(-) diff --git a/mm/sparse.c b/mm/sparse.c index 4267d09b656b..dd0c2dd08ee2 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -807,23 +807,24 @@ static void section_deactivate(struct pglist_data *pgdat, unsigned long pfn, unsigned long mask = section_active_mask(pfn, nr_pages), flags; pgdat_resize_lock(pgdat, &flags); - if (!ms->usage) { - mask = 0; - } else if ((ms->usage->map_active & mask) != mask) { - WARN(1, "section already deactivated active: %#lx mask: %#lx\n", - ms->usage->map_active, mask); - mask = 0; - } else { - early_section = is_early_section(ms); - ms->usage->map_active ^= mask; - if (ms->usage->map_active == 0) { - usage = ms->usage; - ms->usage = NULL; - memmap = sparse_decode_mem_map(ms->section_mem_map, - section_nr); - ms->section_mem_map = 0; - } + if (!ms->usage || + WARN((ms->usage->map_active & mask) != mask, + "section already deactivated active: %#lx mask: %#lx\n", + ms->usage->map_active, mask)) { + pgdat_resize_unlock(pgdat, &flags); + return; } + + early_section = is_early_section(ms); + ms->usage->map_active ^= mask; + if (ms->usage->map_active == 0) { + usage = ms->usage; + ms->usage = NULL; + memmap = sparse_decode_mem_map(ms->section_mem_map, + section_nr); + ms->section_mem_map = 0; + } + pgdat_resize_unlock(pgdat, &flags); /* -- 2.9.0