linux-kernel - Re: [PATCH v2] usb: typec: tcpm: Migrate workqueue to RT priority for processing events

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Date:   Wed, 29 Jul 2020 20:03:37 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Badhri Jagan Sridharan <badhri@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb: typec: tcpm: Migrate workqueue to RT priority for
 processing events

On 7/29/20 7:28 PM, Badhri Jagan Sridharan wrote:
> Hi Greg,
> 
> Sure just sent the new patch v3.
> 
> Patch applies cleanly on my end. So wondering what I am missing.

I expected your patch to conflict with Hans' patch series.
Maybe those are in a different tree/branch ?

Guenter

> Just in case if you are still noticing merge conflicts.
> 
> Here is the git log of my local tree:
> 633198cd2945b7 (HEAD -> usb-next-1) usb: typec: tcpm: Migrate workqueue to RT priority for processing events
> fa56dd9152ef95 (origin/usb-next) Merge tag 'usb-serial-5.9-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial into usb-next
> 25252919a1050e xhci: dbgtty: Make some functions static
> b0e02550346e67 xhci: dbc: Make function xhci_dbc_ring_alloc() static
> ca6377900974c3 Revert "usb: dwc2: override PHY input signals with usb role switch support"
> 09df709cb5aeb2 Revert "usb: dwc2: don't use ID/Vbus detection if usb-role-switch on STM32MP15 SoCs"
> 17a82716587e9d USB: iowarrior: fix up report size handling for some devices
> e98ba8cc3f8a89 Merge tag 'usb-for-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb <http://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb> into usb-next
> c97793089b11f7 Merge 5.8-rc7 into usb-next
> 92ed301919932f (tag: v5.8-rc7, origin/usb-linus, origin/main) Linux 5.8-rc7
> 
> Was comparing against https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/log/?h=usb-next
> 
> Thanks,
> Badhri
> 
> On Wed, Jul 29, 2020 at 7:53 AM Greg Kroah-Hartman <gregkh@...uxfoundation.org <mailto:gregkh@...uxfoundation.org>> wrote:
> 
>     On Thu, Jul 23, 2020 at 07:05:51PM -0700, Badhri Jagan Sridharan wrote:
>     > "tReceiverResponse 15 ms Section 6.6.2
>     > The receiver of a Message requiring a response Shall respond
>     > within tReceiverResponse in order to ensure that the
>     > sender’s SenderResponseTimer does not expire."
>     >
>     > When the cpu complex is busy running other lower priority
>     > work items, TCPM's work queue sometimes does not get scheduled
>     > on time to meet the above requirement from the spec.
>     > Moving to kthread_work apis to run with real time priority.
>     > Just lower than the default threaded irq priority,
>     > MAX_USER_RT_PRIO/2 + 1. (Higher number implies lower priority).
>     >
>     > Further, as observed in 1ff688209e2e, moving to hrtimers to
>     > overcome scheduling latency while scheduling the delayed work.
>     >
>     > TCPM has three work streams:
>     > 1. tcpm_state_machine
>     > 2. vdm_state_machine
>     > 3. event_work
>     >
>     > tcpm_state_machine and vdm_state_machine both schedule work in
>     > future i.e. delayed. Hence each of them have a corresponding
>     > hrtimer, tcpm_state_machine_timer & vdm_state_machine_timer.
>     >
>     > When work is queued right away kthread_queue_work is used.
>     > Else, the relevant timer is programmed and made to queue
>     > the kthread_work upon timer expiry.
>     >
>     > kthread_create_worker only creates one kthread worker thread,
>     > hence single threadedness of workqueue is retained.
>     >
>     > Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com <mailto:badhri@...gle.com>>
> 
>     This doesn't apply against my usb-next branch at all.
> 
>     Can you rebase and resend?
> 
>     Remember to collect the reviewed-by tags as well when you do so.
> 
>     thanks,
> 
>     greg k-h
>