Re: [PATCH v2] PM: hibernate: use acquire/release ordering when compress/decompress image

From: Hongchen Zhang
Date: Tue Dec 12 2023 - 20:04:05 EST

Hi Rafael,
Thanks for your review.
On 2023/12/12 下午9:03, Rafael J. Wysocki wrote:
On Thu, Nov 16, 2023 at 1:56 AM Hongchen Zhang
<zhanghongchen@xxxxxxxxxxx> wrote:

When we test S4(suspend to disk) on LoongArch 3A6000 platform, the
test case sometimes fails. The dmesg log shows the following error:
Invalid LZO compressed length
After we dig into the code, we find out that:
When compress/decompress the image, the synchronization operation
between the control thread and the compress/decompress/crc thread
uses relaxed ordering interface, which is unreliable, and the
following situation may occur:
CPU 0 CPU 1
save_image_lzo lzo_compress_threadfn
atomic_set(&d->stop, 1);
atomic_read(&data[thr].stop)
data[thr].cmp = data[thr].cmp_len;
WRITE data[thr].cmp_len
Then CPU0 get a old cmp_len and write to disk. When cpu resume from S4,
wrong cmp_len is loaded.

To maintain data consistency between two threads, we should use the
acquire/release ordering interface. So we change atomic_read/atomic_set
to atomic_read_acquire/atomic_set_release.

Fixes: 081a9d043c98 ("PM / Hibernate: Improve performance of LZO/plain hibernation, checksum image")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hongchen Zhang <zhanghongchen@xxxxxxxxxxx>
Signed-off-by: Weihao Li <liweihao@xxxxxxxxxxx>

I was about to apply this patch when I noticed the S-o-b confusion.

Either a From: header pointing to Weihao Li <liweihao@xxxxxxxxxxx> is
missing and the Hongchen Zhang <zhanghongchen@xxxxxxxxxxx> sign-off
means that the patch is sent on behalf of Weihao Li, or you both
worked on the patch together and a Co-developed-by: tag pointing to
Weihao Li <liweihao@xxxxxxxxxxx> is missing.

Which of the above is the case?
Yes, we both worked on this patch,let me add
Co-developed-by: Weihao Li <liweihao@xxxxxxxxxxx>
and send V3.


---
v1 -> v2:
1. add Cc: stable@xxxxxxxxxxxxxxx in commit log
2. add Fixes: line in commit log
---
kernel/power/swap.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index a2cb0babb5ec..d44f5937f1e5 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -606,11 +606,11 @@ static int crc32_threadfn(void *data)
unsigned i;

while (1) {
- wait_event(d->go, atomic_read(&d->ready) ||
+ wait_event(d->go, atomic_read_acquire(&d->ready) ||
kthread_should_stop());
if (kthread_should_stop()) {
d->thr = NULL;
- atomic_set(&d->stop, 1);
+ atomic_set_release(&d->stop, 1);
wake_up(&d->done);
break;
}
@@ -619,7 +619,7 @@ static int crc32_threadfn(void *data)
for (i = 0; i < d->run_threads; i++)
*d->crc32 = crc32_le(*d->crc32,
d->unc[i], *d->unc_len[i]);
- atomic_set(&d->stop, 1);
+ atomic_set_release(&d->stop, 1);
wake_up(&d->done);
}
return 0;
@@ -649,12 +649,12 @@ static int lzo_compress_threadfn(void *data)
struct cmp_data *d = data;

while (1) {
- wait_event(d->go, atomic_read(&d->ready) ||
+ wait_event(d->go, atomic_read_acquire(&d->ready) ||
kthread_should_stop());
if (kthread_should_stop()) {
d->thr = NULL;
d->ret = -1;
- atomic_set(&d->stop, 1);
+ atomic_set_release(&d->stop, 1);
wake_up(&d->done);
break;
}
@@ -663,7 +663,7 @@ static int lzo_compress_threadfn(void *data)
d->ret = lzo1x_1_compress(d->unc, d->unc_len,
d->cmp + LZO_HEADER, &d->cmp_len,
d->wrk);
- atomic_set(&d->stop, 1);
+ atomic_set_release(&d->stop, 1);
wake_up(&d->done);
}
return 0;
@@ -798,7 +798,7 @@ static int save_image_lzo(struct swap_map_handle *handle,

data[thr].unc_len = off;

- atomic_set(&data[thr].ready, 1);
+ atomic_set_release(&data[thr].ready, 1);
wake_up(&data[thr].go);
}

@@ -806,12 +806,12 @@ static int save_image_lzo(struct swap_map_handle *handle,
break;

crc->run_threads = thr;
- atomic_set(&crc->ready, 1);
+ atomic_set_release(&crc->ready, 1);
wake_up(&crc->go);

for (run_threads = thr, thr = 0; thr < run_threads; thr++) {
wait_event(data[thr].done,
- atomic_read(&data[thr].stop));
+ atomic_read_acquire(&data[thr].stop));
atomic_set(&data[thr].stop, 0);

ret = data[thr].ret;
@@ -850,7 +850,7 @@ static int save_image_lzo(struct swap_map_handle *handle,
}
}

- wait_event(crc->done, atomic_read(&crc->stop));
+ wait_event(crc->done, atomic_read_acquire(&crc->stop));
atomic_set(&crc->stop, 0);
}

@@ -1132,12 +1132,12 @@ static int lzo_decompress_threadfn(void *data)
struct dec_data *d = data;

while (1) {
- wait_event(d->go, atomic_read(&d->ready) ||
+ wait_event(d->go, atomic_read_acquire(&d->ready) ||
kthread_should_stop());
if (kthread_should_stop()) {
d->thr = NULL;
d->ret = -1;
- atomic_set(&d->stop, 1);
+ atomic_set_release(&d->stop, 1);
wake_up(&d->done);
break;
}
@@ -1150,7 +1150,7 @@ static int lzo_decompress_threadfn(void *data)
flush_icache_range((unsigned long)d->unc,
(unsigned long)d->unc + d->unc_len);

- atomic_set(&d->stop, 1);
+ atomic_set_release(&d->stop, 1);
wake_up(&d->done);
}
return 0;
@@ -1335,7 +1335,7 @@ static int load_image_lzo(struct swap_map_handle *handle,
}

if (crc->run_threads) {
- wait_event(crc->done, atomic_read(&crc->stop));
+ wait_event(crc->done, atomic_read_acquire(&crc->stop));
atomic_set(&crc->stop, 0);
crc->run_threads = 0;
}
@@ -1371,7 +1371,7 @@ static int load_image_lzo(struct swap_map_handle *handle,
pg = 0;
}

- atomic_set(&data[thr].ready, 1);
+ atomic_set_release(&data[thr].ready, 1);
wake_up(&data[thr].go);
}

@@ -1390,7 +1390,7 @@ static int load_image_lzo(struct swap_map_handle *handle,

for (run_threads = thr, thr = 0; thr < run_threads; thr++) {
wait_event(data[thr].done,
- atomic_read(&data[thr].stop));
+ atomic_read_acquire(&data[thr].stop));
atomic_set(&data[thr].stop, 0);

ret = data[thr].ret;
@@ -1421,7 +1421,7 @@ static int load_image_lzo(struct swap_map_handle *handle,
ret = snapshot_write_next(snapshot);
if (ret <= 0) {
crc->run_threads = thr + 1;
- atomic_set(&crc->ready, 1);
+ atomic_set_release(&crc->ready, 1);
wake_up(&crc->go);
goto out_finish;
}
@@ -1429,13 +1429,13 @@ static int load_image_lzo(struct swap_map_handle *handle,
}

crc->run_threads = thr;
- atomic_set(&crc->ready, 1);
+ atomic_set_release(&crc->ready, 1);
wake_up(&crc->go);
}

out_finish:
if (crc->run_threads) {
- wait_event(crc->done, atomic_read(&crc->stop));
+ wait_event(crc->done, atomic_read_acquire(&crc->stop));
atomic_set(&crc->stop, 0);
}
stop = ktime_get();
--
2.33.0



--
Best Regards
Hongchen Zhang