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authorLiu Shixin <liushixin2@huawei.com>2021-11-05 23:43:59 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-11-06 23:30:41 +0300
commitaf1c31acc85325aec2bcc5941fb7a02e19143503 (patch)
tree565f062886ae3d2c64093492c0ecfc094d8f4006 /mm/vmstat.c
parent325254899684adf32b95ae59000dec4a6853e930 (diff)
downloadlinux-af1c31acc85325aec2bcc5941fb7a02e19143503.tar.xz
mm/vmstat: annotate data race for zone->free_area[order].nr_free
KCSAN reports a data-race on v5.10 which also exists on mainline: BUG: KCSAN: data-race in extfrag_for_order+0x33/0x2d0 race at unknown origin, with read to 0xffff9ee9bfffab48 of 8 bytes by task 34 on cpu 1: extfrag_for_order+0x33/0x2d0 kcompactd+0x5f0/0xce0 kthread+0x1f9/0x220 ret_from_fork+0x22/0x30 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 34 Comm: kcompactd0 Not tainted 5.10.0+ #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 Access to zone->free_area[order].nr_free in extfrag_for_order() and frag_show_print() is lockless. That's intentional and the stats are a rough estimate anyway. Annotate them with data_race(). [liushixin2@huawei.com: add comments] Link: https://lkml.kernel.org/r/20210918084655.2696522-1-liushixin2@huawei.com Link: https://lkml.kernel.org/r/20210908015606.3999871-1-liushixin2@huawei.com Signed-off-by: Liu Shixin <liushixin2@huawei.com> Cc: "Paul E . McKenney" <paulmck@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmstat.c')
-rw-r--r--mm/vmstat.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 0f4643e5324d..0fde7470368d 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1070,8 +1070,13 @@ static void fill_contig_page_info(struct zone *zone,
for (order = 0; order < MAX_ORDER; order++) {
unsigned long blocks;
- /* Count number of free blocks */
- blocks = zone->free_area[order].nr_free;
+ /*
+ * Count number of free blocks.
+ *
+ * Access to nr_free is lockless as nr_free is used only for
+ * diagnostic purposes. Use data_race to avoid KCSAN warning.
+ */
+ blocks = data_race(zone->free_area[order].nr_free);
info->free_blocks_total += blocks;
/* Count free base pages */
@@ -1446,7 +1451,11 @@ static void frag_show_print(struct seq_file *m, pg_data_t *pgdat,
seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
for (order = 0; order < MAX_ORDER; ++order)
- seq_printf(m, "%6lu ", zone->free_area[order].nr_free);
+ /*
+ * Access to nr_free is lockless as nr_free is used only for
+ * printing purposes. Use data_race to avoid KCSAN warning.
+ */
+ seq_printf(m, "%6lu ", data_race(zone->free_area[order].nr_free));
seq_putc(m, '\n');
}