From: Michael Kelley <mikelley@microsoft.com>
To: Andrea Parri <parri.andrea@gmail.com>, vkuznets <vkuznets@redhat.com>
Cc: Dexuan Cui <decui@microsoft.com>,
KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Wei Liu <wei.liu@kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [RFC PATCH 02/11] Drivers: hv: vmbus: Don't bind the offer&rescind works to a specific CPU
Date: Sun, 29 Mar 2020 03:43:26 +0000 [thread overview]
Message-ID: <MW2PR2101MB1052A2E44557B29C191F557DD7CA0@MW2PR2101MB1052.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20200328170833.GA10153@andrea>
From: Andrea Parri <parri.andrea@gmail.com> Sent: Saturday, March 28, 2020 10:09 AM
>
> > In case we believe that OFFER -> RESCINF sequence is always ordered
> > by the host AND we don't care about other offers in the queue the
> > suggested locking is OK: we're guaranteed to process RESCIND after we
> > finished processing OFFER for the same channel. However, waiting for
> > 'offer_in_progress == 0' looks fishy so I'd suggest we at least add a
> > comment explaining that the wait is only needed to serialize us with
> > possible OFFER for the same channel - and nothing else. I'd personally
> > still slightly prefer the algorythm I suggested as it guarantees we take
> > channel_mutex with offer_in_progress == 0 -- even if there are no issues
> > we can think of today (not strongly though).
>
> Does it? offer_in_progress is incremented without channel_mutex...
>
> IAC, I have no objections to apply the changes you suggested. To avoid
> misunderstandings: vmbus_bus_suspend() presents a similar usage... Are
> you suggesting that I apply similar changes there?
>
> Alternatively: FWIW, the comment in vmbus_onoffer_rescind() does refer
> to "The offer msg and the corresponding rescind msg...". I am all ears
> if you have any concrete suggestions to improve these comments.
>
Given that waiting for 'offer_in_progress == 0' is the current code, I think
there's an argument to made for not changing it if the change isn't strictly
necessary. This patch set introduces enough change that *is* necessary. :-)
Michael
next prev parent reply other threads:[~2020-03-29 3:43 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 22:54 [RFC PATCH 00/11] VMBus channel interrupt reassignment Andrea Parri (Microsoft)
2020-03-25 22:54 ` [RFC PATCH 01/11] Drivers: hv: vmbus: Always handle the VMBus messages on CPU0 Andrea Parri (Microsoft)
2020-03-26 14:05 ` Vitaly Kuznetsov
2020-03-28 18:50 ` Andrea Parri
2020-03-25 22:54 ` [RFC PATCH 02/11] Drivers: hv: vmbus: Don't bind the offer&rescind works to a specific CPU Andrea Parri (Microsoft)
2020-03-26 14:16 ` Vitaly Kuznetsov
2020-03-26 15:47 ` Andrea Parri
2020-03-26 17:26 ` Vitaly Kuznetsov
2020-03-28 17:08 ` Andrea Parri
2020-03-29 3:43 ` Michael Kelley [this message]
2020-03-30 12:24 ` Vitaly Kuznetsov
2020-04-03 12:04 ` Andrea Parri
2020-03-25 22:54 ` [RFC PATCH 03/11] Drivers: hv: vmbus: Replace the per-CPU channel lists with a global array of channels Andrea Parri (Microsoft)
2020-03-26 14:31 ` Vitaly Kuznetsov
2020-03-26 17:05 ` Andrea Parri
2020-03-26 17:43 ` Vitaly Kuznetsov
2020-03-28 18:21 ` Andrea Parri
2020-03-29 3:49 ` Michael Kelley
2020-03-30 12:45 ` Vitaly Kuznetsov
2020-04-03 13:38 ` Andrea Parri
2020-04-03 14:56 ` Vitaly Kuznetsov
2020-03-25 22:54 ` [RFC PATCH 04/11] hv_netvsc: Disable NAPI before closing the VMBus channel Andrea Parri (Microsoft)
2020-03-26 15:26 ` Stephen Hemminger
2020-03-26 17:55 ` Andrea Parri
2020-03-25 22:54 ` [RFC PATCH 05/11] hv_utils: Always execute the fcopy and vss callbacks in a tasklet Andrea Parri (Microsoft)
2020-03-25 22:55 ` [RFC PATCH 06/11] Drivers: hv: vmbus: Use a spin lock for synchronizing channel scheduling vs. channel removal Andrea Parri (Microsoft)
2020-03-25 22:55 ` [RFC PATCH 07/11] PCI: hv: Prepare hv_compose_msi_msg() for the VMBus-channel-interrupt-to-vCPU reassignment functionality Andrea Parri (Microsoft)
2020-03-25 22:55 ` [RFC PATCH 08/11] Drivers: hv: vmbus: Remove the unused HV_LOCALIZED channel affinity logic Andrea Parri (Microsoft)
2020-03-25 22:55 ` [RFC PATCH 09/11] Drivers: hv: vmbus: Synchronize init_vp_index() vs. CPU hotplug Andrea Parri (Microsoft)
2020-03-25 22:55 ` [RFC PATCH 10/11] Drivers: hv: vmbus: Introduce the CHANNELMSG_MODIFYCHANNEL message type Andrea Parri (Microsoft)
2020-03-26 14:46 ` Vitaly Kuznetsov
2020-03-28 18:48 ` Andrea Parri
2020-04-03 14:55 ` Andrea Parri
2020-03-25 22:55 ` [RFC PATCH 11/11] scsi: storvsc: Re-init stor_chns when a channel interrupt is re-assigned Andrea Parri (Microsoft)
2020-03-30 16:42 ` Michael Kelley
2020-03-30 18:55 ` Andrea Parri
2020-03-30 19:49 ` Michael Kelley
2020-04-03 13:41 ` Andrea Parri
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