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mm/slub: mark racy accesses on slab->slabs

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The reads of slab->slabs are racy because it may be changed by
put_cpu_partial concurrently. In slabs_cpu_partial_show() and
show_slab_objects(), slab->slabs is only used for showing information.

Data-racy reads from shared variables that are used only for diagnostic
purposes should typically use data_race(), since it is normally not a
problem if the values are off by a little.

This patch is aimed at reducing the number of benign races reported by
KCSAN in order to focus future debugging effort on harmful races.

Signed-off-by: linke li <lilinke99@qq.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
linke li 2024-03-21 11:48:15 +08:00 committed by Vlastimil Babka
parent ad7c5ebead
commit 87654cf7a9
1 changed files with 3 additions and 3 deletions
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6
mm/slub.c
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@ -6036,7 +6036,7 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
else if (flags & SO_OBJECTS)
WARN_ON_ONCE(1);
else
x = slab->slabs;
x = data_race(slab->slabs);
total += x;
nodes[node] += x;
}
@ -6241,7 +6241,7 @@ static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf)
slab = slub_percpu_partial(per_cpu_ptr(s->cpu_slab, cpu));
if (slab)
slabs += slab->slabs;
slabs += data_race(slab->slabs);
}
#endif
@ -6255,7 +6255,7 @@ static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf)
slab = slub_percpu_partial(per_cpu_ptr(s->cpu_slab, cpu));
if (slab) {
slabs = READ_ONCE(slab->slabs);
slabs = data_race(slab->slabs);
objects = (slabs * oo_objects(s->oo)) / 2;
len += sysfs_emit_at(buf, len, " C%d=%d(%d)",
cpu, objects, slabs);