Messages in this thread | | | Date | Thu, 28 Mar 2019 17:26:42 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] Convert struct pid count to refcount_t |
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On 03/28, Jann Horn wrote: > > Since we're just talking about RCU stuff now, adding Paul McKenney to > the thread.
Since you added Paul let me add more confusion to this thread ;)
There were some concerns about the lack of barriers in put_pid(), but I can't find that old discussion and I forgot the result of that discussion...
Paul, could you confirm that this code
CPU_0 CPU_1
X = 1; if (READ_ONCE(Y)) mb(); X = 2; Y = 1; BUG_ON(X != 2);
is correct? I think it is, control dependency pairs with mb(), right?
If not, then put_pid() needs atomic_read_acquire() as it was proposed in that discussion.
Oleg.
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