On 2022/8/25 16:22, David Hildenbrand wrote:
On 25.08.22 04:34, Kefeng Wang wrote:
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;
}
I'd much rather just use a dedicated lock that does not involve memory
hotplug.
The issue only occurred due memory hotplug, without mem-hotplug,
the kswapd won't stop or re-run, there is no above issue too, add a new
lock would be duplicated, but the scope of protection is smaller, I could
repost with new lock if no more comment.
