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Subject: Re: [PATCH v2] PM: hibernate: use acquire/release ordering when
 compress/decompress image
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        Bojan Smojver <bojan@rexursive.com>, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org, loongson-kernel@lists.loongnix.cn,
        stable@vger.kernel.org, Weihao Li <liweihao@loongson.cn>
References: <20231116005609.1583858-1-zhanghongchen@loongson.cn>
 <CAJZ5v0gTcntizfqKMa0YxHbOhNsLf=nAEoOBf2f9fFt-uzzgsg@mail.gmail.com>
From:   Hongchen Zhang <zhanghongchen@loongson.cn>
Message-ID: <ee169c10-7c49-898a-caee-124ec3254330@loongson.cn>
Date:   Wed, 13 Dec 2023 09:02:57 +0800
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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@loongson.cn> 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@vger.kernel.org
>> Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>
>> Signed-off-by: Weihao Li <liweihao@loongson.cn>
> 
> I was about to apply this patch when I noticed the S-o-b confusion.
> 
> Either a From: header pointing to Weihao Li <liweihao@loongson.cn> is
> missing and the Hongchen Zhang <zhanghongchen@loongson.cn> 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@loongson.cn> 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@loongson.cn>
and send V3.

> 
>> ---
>> v1 -> v2:
>>          1. add Cc: stable@vger.kernel.org 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