Re: [PATCH 3/4] KVM: introduce memory transaction semaphore

Emanuele Giuseppe Esposito
2022-10-24T15:06:16Z

Am 23/10/2022 um 19:50 schrieb Paolo Bonzini:
> On 10/22/22 17:48, Emanuele Giuseppe Esposito wrote:
>> +static DECLARE_RWSEM(memory_transaction);
>
> This cannot be global, it must be per-struct kvm.  Otherwise one VM can
> keep the rwsem indefinitely while a second VM hangs in
> KVM_KICK_ALL_RUNNING_VCPUS.
>
> It can also be changed to an SRCU (with the down_write+up_write sequence
> changed to synchronize_srcu_expedited) which has similar characteristics
> to your use of the rwsem.
>

Makes sense, but why synchronize_srcu_expedited and not synchronize_srcu?

Thank you,
Emanuele