From: Stewart Smith <stewart@linux.vnet.ibm.com>
To: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Samuel Mendoza-Jonas <sam@mendozajonas.com>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        Jiri Slaby <jslaby@suse.com>
Subject: Re: [PATCH] tty/hvc: Use IRQF_SHARED for hvc consoles
In-Reply-To: <1458262483-15149-1-git-send-email-sam@mendozajonas.com>
References: <1458262483-15149-1-git-send-email-sam@mendozajonas.com>
User-Agent: Notmuch/0.21+24~gbceb651 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-redhat-linux-gnu)
Date: Wed, 23 Mar 2016 16:17:56 +1100
Message-ID: <87twjxydq3.fsf@birb.au.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1214
Lines: 32

Samuel Mendoza-Jonas <sam@mendozajonas.com> writes:
> Commit 2def86a7200c
> ("hvc: Convert to using interrupts instead of opal events")
> enabled the use of interrupts in the hvc_driver for OPAL platforms.
> However on machines with more than one hvc console, any console after
> the first will fail to register an interrupt handler in
> notifier_add_irq() since all consoles share the same IRQ number but do
> not set the IRQF_SHARED flag:
>
> [   51.179907] genirq: Flags mismatch irq 31. 00000000 (hvc_console) vs.
> 00000000 (hvc_console)
> [   51.180010] hvc_open: request_irq failed with rc -16.
>
> This error propagates up to hvc_open() and the console is closed, but
> OPAL will still generate interrupts that are not handled, leading to
> rcu_sched stall warnings.
>
> Set IRQF_SHARED when calling request_irq, allowing additional consoles
> to start properly.
>
> Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
> Cc: <stable@vger.kernel.org> # 4.1.x-

Tested on 4.4.6 - seemed to stop (some of) the problems I was having
when using it as a kernel for the bootloader on a FSP based POWER8
system.

Tested-by: Stewart Smith <stewart@linux.vnet.ibm.com>

-- 
Stewart Smith
OPAL Architect, IBM.