From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>
Cc: <muchun.song@linux.dev>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm: slince possible data races about pgdat->kswapd
Date: Thu, 25 Aug 2022 10:34:18 +0800 [thread overview]
Message-ID: <fe06a35b-229f-c143-0200-33dbb315f0fe@huawei.com> (raw)
In-Reply-To: <e5223895-6319-1911-28bf-09449ded96c9@redhat.com>
On 2022/8/24 16:24, David Hildenbrand wrote:
> On 24.08.22 09:19, Kefeng Wang wrote:
>> The pgdat->kswapd could be accessed concurrently by kswapd_run() and
>> kcompactd(), it don't be protected by any lock, which could leads to
>> data races, adding READ/WRITE_ONCE() to slince it.
> Okay, I think this patch here makes it clearer that we really just want
> proper synchronization instead of hacking around it.
>
> What speaks against protecting pgdat->kswapd this using some proper
> locking primitive?
as comments about kswapd in struct pglist_data, pgdat->kswapd should be
protected by mem_hotplug_begin/done(), how about this way?
diff --git a/mm/compaction.c b/mm/compaction.c
index 640fa76228dd..62018f35242a 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1983,7 +1983,13 @@ static inline bool is_via_compact_memory(int order)
static bool kswapd_is_running(pg_data_t *pgdat)
{
- return pgdat->kswapd && task_is_running(pgdat->kswapd);
+ bool running;
+
+ mem_hotplug_begin();
+ running = pgdat->kswapd && task_is_running(pgdat->kswapd);
+ mem_hotplug_end();
+
+ return running;
}
next prev parent reply other threads:[~2022-08-25 2:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-24 7:19 [PATCH 1/2] mm: fix null-ptr-deref in kswapd_is_running() Kefeng Wang
2022-08-24 7:19 ` [PATCH 2/2] mm: slince possible data races about pgdat->kswapd Kefeng Wang
2022-08-24 8:24 ` David Hildenbrand
2022-08-24 9:51 ` Kefeng Wang
2022-08-25 2:34 ` Kefeng Wang [this message]
2022-08-25 8:22 ` David Hildenbrand
2022-08-25 9:48 ` Kefeng Wang
2022-08-24 7:56 ` [PATCH 1/2] mm: fix null-ptr-deref in kswapd_is_running() David Hildenbrand
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