Messages in this thread | | | Date | Tue, 25 Oct 2022 12:01:29 +0200 | Subject | Re: [PATCH 3/4] KVM: introduce memory transaction semaphore | From | Paolo Bonzini <> |
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On 10/24/22 14:57, Emanuele Giuseppe Esposito wrote: > > > 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?
Because (thanks to the kick) you expect the grace period to end almost immediately, and synchronize_srcu() will slow down sensibly the changes to the memory map.
Paolo
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