Messages in this thread | | | Subject | Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page() | From | Paolo Bonzini <> | Date | Thu, 10 Mar 2016 17:04:49 +0100 |
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On 10/03/2016 16:45, Xiao Guangrong wrote: >> >>> Compared to smp_load_acquire(), smp_mb() adds an ordering between stores >>> and loads. >> >> Here, the ordering is load-store, hence... > > Yes, this is why i put smp_mb() in the code. :)
Here is a table of barriers:
'. after| | before '. | load | store __________'.|___________________|________________________ | | | smp_rmb | smp_load_acquire load | smp_load_acquire | smp_store_release XX | smp_mb | smp_mb ____________|___________________|________________________ | | | | smp_wmb store | smp_mb | smp_store_release | | smp_mb | |
Your case is the one marked with XX, so a smp_load_acquire() is enough---and it's preferrable, because it's cheaper than smp_mb() and more self-documenting.
Paolo
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