On Mon, 16 Mar 2015 10:06:37 +0800, Lee said: > I am studying the dcache in VFS recently . I found that hlist of dcache > is already protected by RCU in > __d_lookup.Is it necessary for the function -- d_lookup using > sequence lock to protect the hlist again?
RCU is useful when you can tolerate a bit of latency in other users finding out about updated values and/or slightly stale values. That's not an option for d_lookup(), which has to check the most recent value in order to avoid race conditions.
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