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From: Nick Desaulniers <nick.desaulniers@gmail.com>
Cc: akpm@linux-foundation.org, hannes@cmpxchg.org,
	mgorman@techsingularity.net, mhocko@suse.com, vbabka@suse.cz,
	minchan@kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	Nick Desaulniers <nick.desaulniers@gmail.com>
Subject: [PATCH] mm/vmscan: fix unsequenced modification and access warning
Date: Tue,  9 May 2017 23:53:28 -0700	[thread overview]
Message-ID: <20170510065328.9215-1-nick.desaulniers@gmail.com> (raw)

Clang flags this file with the -Wunsequenced error that GCC does not
have.

unsequenced modification and access to 'gfp_mask'

It seems that gfp_mask is both read and written without a sequence point
in between, which is undefined behavior.

Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
---
 mm/vmscan.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4e7ed65842af..74785908822c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2958,7 +2958,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 	unsigned long nr_reclaimed;
 	struct scan_control sc = {
 		.nr_to_reclaim = SWAP_CLUSTER_MAX,
-		.gfp_mask = (gfp_mask = current_gfp_context(gfp_mask)),
+		.gfp_mask = current_gfp_context(gfp_mask),
 		.reclaim_idx = gfp_zone(gfp_mask),
 		.order = order,
 		.nodemask = nodemask,
@@ -2968,6 +2968,8 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 		.may_swap = 1,
 	};
 
+	gfp_mask = sc.gfp_mask;
+
 	/*
 	 * Do not enter reclaim if fatal signal was delivered while throttled.
 	 * 1 is returned so that the page allocator does not OOM kill at this
-- 
2.11.0

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             reply	other threads:[~2017-05-10  6:54 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-10  6:53 Nick Desaulniers [this message]
2017-05-10  7:15 ` [PATCH] mm/vmscan: fix unsequenced modification and access warning Michal Hocko
2017-05-10  8:27   ` [Patch v2] " Nick Desaulniers
2017-05-10  8:38     ` Michal Hocko
2017-05-16  8:27       ` Michal Hocko
2017-05-17  3:01         ` Nick Desaulniers
2017-05-26  4:43         ` Nick Desaulniers
2017-05-31 15:21           ` Michal Hocko
2017-05-10  8:46   ` [PATCH] " Nick Desaulniers
2017-05-10  9:25     ` Michal Hocko
2017-05-10 15:40       ` [Patch v3] " Nick Desaulniers
2018-03-21 21:37   ` [PATCH] " Nick Desaulniers
2018-03-22  9:50     ` Michal Hocko

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