linux-kernel - RE: [PATCH] scsi: storvsc: Prevent running tasklet for long

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Message-ID: <a9af8d8d5ee24d19a87c3353a4e8941d@AcuMS.aculab.com>
Date:   Wed, 6 Jul 2022 11:09:43 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Praveen Kumar' <kumarpraveen@...ux.microsoft.com>,
        Saurabh Sengar <ssengar@...ux.microsoft.com>,
        "kys@...rosoft.com" <kys@...rosoft.com>,
        "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
        "sthemmin@...rosoft.com" <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "decui@...rosoft.com" <decui@...rosoft.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ssengar@...rosoft.com" <ssengar@...rosoft.com>,
        "mikelley@...rosoft.com" <mikelley@...rosoft.com>
Subject: RE: [PATCH] scsi: storvsc: Prevent running tasklet for long

From: Praveen Kumar
> Sent: 06 July 2022 10:15
> 
> On 05-07-2022 21:02, Saurabh Sengar wrote:
> > There can be scenarios where packets in ring buffer are continuously
> > getting queued from upper layer and dequeued from storvsc interrupt
> > handler, such scenarios can hold the foreach_vmbus_pkt loop (which is
> > executing as a tasklet) for a long duration. Theoretically its possible
> > that this loop executes forever. Add a condition to limit execution of
> > this tasklet for finite amount of time to avoid such hazardous scenarios.

Does this really make much difference?

I'd guess the tasklet gets immediately rescheduled as soon as
the upper layer queues another packet?

Or do you get a different 'bug' where it is never woken again
because the ring is stuck full?

	David

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