Messages in this thread | | | Date | Thu, 11 Nov 2021 11:47:57 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v4 01/17] perf: Protect perf_guest_cbs with RCU |
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On Thu, Nov 11, 2021 at 08:26:58AM +0100, Paolo Bonzini wrote: > On 11/11/21 03:07, Sean Christopherson wrote:
> > EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks); > > int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs) > > { > > - perf_guest_cbs = NULL; > > + if (WARN_ON_ONCE(rcu_access_pointer(perf_guest_cbs) != cbs)) > > + return -EINVAL; > > + > > + rcu_assign_pointer(perf_guest_cbs, NULL); > > + synchronize_rcu(); > This technically could be RCU_INIT_POINTER but it's not worth a respin. > There are dozens of other occurrences, and if somebody wanted they > could use Coccinelle to fix all of them.
I've been pushing the other way, trying to get rid of RCU_INIT_POINTER() since rcu_assign_pointer(, NULL) actualy DTRT per __builtin_constant_p() etc.
There's a very few sites where we use RCU_INIT_POINTER() with a !NULL argument, and those are 'special'.
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