From: Qian Cai <cai@lca.pw>
To: akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>
Subject: [PATCH -next] mm/swap_state: mark an intentional data race
Date: Wed, 5 Feb 2020 22:55:16 -0500 [thread overview]
Message-ID: <20200206035516.2593-1-cai@lca.pw> (raw)
swap_cache_info.find_total could be accessed concurrently as noticed by
KCSAN,
BUG: KCSAN: data-race in lookup_swap_cache / lookup_swap_cache
write to 0xffffffff85517318 of 8 bytes by task 94138 on cpu 101:
lookup_swap_cache+0x12e/0x460
lookup_swap_cache at mm/swap_state.c:322
do_swap_page+0x112/0xeb0
__handle_mm_fault+0xc7a/0xd00
handle_mm_fault+0xfc/0x2f0
do_page_fault+0x263/0x6f9
page_fault+0x34/0x40
read to 0xffffffff85517318 of 8 bytes by task 91655 on cpu 100:
lookup_swap_cache+0x117/0x460
lookup_swap_cache at mm/swap_state.c:322
shmem_swapin_page+0xc7/0x9e0
shmem_getpage_gfp+0x2ca/0x16c0
shmem_fault+0xef/0x3c0
__do_fault+0x9e/0x220
do_fault+0x4a0/0x920
__handle_mm_fault+0xc69/0xd00
handle_mm_fault+0xfc/0x2f0
do_page_fault+0x263/0x6f9
page_fault+0x34/0x40
Reported by Kernel Concurrency Sanitizer on:
CPU: 100 PID: 91655 Comm: systemd-journal Tainted: G W O L 5.5.0-next-20200204+ #6
Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
Both the read and write are done as lockless. Since INC_CACHE_INFO() is
only used for swap_cache_info.find_total and
swap_cache_info.find_success which both are information counters, even
if any of them missed a few incremental due to data races, it will be
harmless, so just mark it as an intentional data race using the
data_race() macro.
While at it, fix a checkpatch.pl warning,
WARNING: Single statement macros should not use a do {} while (0) loop
Signed-off-by: Qian Cai <cai@lca.pw>
---
mm/swap_state.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 8e7ce9a9bc5e..b964c1391362 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -58,8 +58,8 @@ static bool enable_vma_readahead __read_mostly = true;
#define GET_SWAP_RA_VAL(vma) \
(atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
-#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
-#define ADD_CACHE_INFO(x, nr) do { swap_cache_info.x += (nr); } while (0)
+#define INC_CACHE_INFO(x) data_race(swap_cache_info.x++)
+#define ADD_CACHE_INFO(x, nr) (swap_cache_info.x += (nr))
static struct {
unsigned long add_total;
--
2.21.0 (Apple Git-122.2)
next reply other threads:[~2020-02-06 3:55 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-06 3:55 Qian Cai [this message]
2020-02-06 20:31 ` [PATCH -next] mm/swap_state: mark an intentional data race Qian Cai
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