> From: Pavel Machek <pavel@xxxxxxx> > Sent: Tuesday, May 5, 2020 5:10 AM > To: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; Dexuan Cui > <decui@xxxxxxxxxxxxx>; Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > Subject: Re: [PATCH 4.19 11/37] PM: hibernate: Freeze kernel threads in > software_resume() > > Hi! > > > commit 2351f8d295ed63393190e39c2f7c1fee1a80578f upstream. > > > > Currently the kernel threads are not frozen in software_resume(), so > > between dpm_suspend_start(PMSG_QUIESCE) and resume_target_kernel(), > > system_freezable_power_efficient_wq can still try to submit SCSI > > commands and this can cause a panic since the low level SCSI driver > > (e.g. hv_storvsc) has quiesced the SCSI adapter and can not accept > > any SCSI commands: https://lkml.org/lkml/2020/4/10/47 > > > > At first I posted a fix (https://lkml.org/lkml/2020/4/21/1318) trying > > to resolve the issue from hv_storvsc, but with the help of > > Bart Van Assche, I realized it's better to fix software_resume(), > > since this looks like a generic issue, not only pertaining to SCSI. > > I believe it is too soon to merge this into stable. It is rather big > hammer. Yes, it is right thing to do. But I'd wait for 5.7 to be > released before merging it to stable. > > It needs some testing and it did not get any. > > Best regards, > Pavel Hi, I did do some testing in a Linux VM running on Hyper-V: Without the patch, I can easily hit the panic I described in the first link above. With the patch, my Linux VM can hibernate >10K times without seeing the panic and I don't see any issue caused by the patch. That being said, I don't mind waiting for 5.7 before we merge the patch to stable. It would be good for the patch to get more testing from others. Thanks, -- Dexuan
