Re: [PATCH v3 0/2] Ensure that the SCSI error handler gets woken up

[Bart Van Assche <Bart.VanAssche@wdc.com>]

On Thu, 2017-12-07 at 12:02 +0000, John Garry wrote:
> On 07/12/2017 01:55, Martin K. Petersen wrote:
> > 
> > Bart,
> > 
> > > As reported by Pavel Tikhomirov it can happen that the SCSI error
> > > handler does not get woken up. This is very annoying because it
> > > results in a queue stall. The two patches in this series address this
> > > issue without acquiring the SCSI host lock in the hot path. Please
> > > consider these patches for kernel v4.16.
> > 
> > Applied to 4.16/scsi-queue. Thank you!
> > 
> 
> Is anyone finding a build error for this patch? I built allmodconfig on 
> Martin's 4.16/scsi-queue and I get this:
> ERROR: "init_rcu_head" [drivers/scsi/scsi_mod.ko] undefined!
> ERROR: "destroy_rcu_head" [drivers/scsi/scsi_mod.ko] undefined!
> 
> Reverting fixes it.
> 
>  From a quick check, it seems the rcu funcitons are not exported, and 
> SCSI=m means hosts.c cannot reference it.

Hello John,

A discussion is ongoing about this issue on the linux-next mailing list.
Paul E. McKenney proposed to export both the init_rcu_head() and
destroy_rcu_head() functions. See also https://lkml.org/lkml/2017/12/6/1150.

Bart.