Subject: Re: Continuous SD IO causes hung task messages

From: Russell King - ARM Linux admin <[email-masked]>
Date: Tue, 27 Aug 2019 15:36:34 +0100

On Tue, Aug 27, 2019 at 03:55:23PM +0200, Ulf Hansson wrote:
> On Tue, 27 Aug 2019 at 15:43, Russell King - ARM Linux admin
> <[email-masked]> wrote:
> >
> > Hi,
> >
> > While dd'ing the contents of a SD card, I get hung task timeout
> > messages as per below.  However, the dd is making progress.  Any
> > ideas?
> >
> > Presumably, mmc_rescan doesn't get a look-in while IO is progressing
> > for the card?
> 
> Is it a regression?
> 
> There not much of recent mmc core and mmc block changes, that I can
> think of at this point.

No idea - I just repaired the SD socket after the D2 line became
disconnected, and decided to run that command as a test.

> > ARM64 host, Macchiatobin, uSD card.
> 
> What mmc host driver is it? mmci?

sdhci-xenon.

I'm just trying with one CPU online, then I'll try with two.  My
suspicion is that there's a problem in the ARM64 arch code where
unlocking a mutex doesn't get noticed on other CPUs.

Hmm, I thought I'd try bringing another CPU online, but it seems
like the ARM64 CPU hotplug code is broken:

[ 3552.029689] CPU1: shutdown
[ 3552.031099] psci: CPU1 killed.
[ 3949.835212] CPU1: failed to come online
[ 3949.837753] CPU1: failed in unknown state : 0x0

which means I can only take CPUs down, I can't bring them back
online without rebooting.

-- 
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