From: "Cédric Le Goater" <clg@kaod.org>
To: <linuxppc-dev@lists.ozlabs.org>
Cc: Laurent Vivier <lvivier@redhat.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>,
stable@vger.kernel.org, David Gibson <dgibson@redhat.com>
Subject: Re: [PATCH] powerpc/xive: Do not skip CPU-less nodes when creating the IPIs
Date: Fri, 6 Aug 2021 13:50:43 +0200 [thread overview]
Message-ID: <481023b5-6857-1331-23cd-e9eabd511821@kaod.org> (raw)
In-Reply-To: <20210629131542.743888-1-clg@kaod.org>
On 6/29/21 3:15 PM, Cédric Le Goater wrote:
> On PowerVM, CPU-less nodes can be populated with hot-plugged CPUs at
> runtime. Today, the IPI is not created for such nodes, and hot-plugged
> CPUs use a bogus IPI, which leads to soft lockups.
>
> We could create the node IPI on demand but it is a bit complex because
> this code would be called under bringup_up() and some IRQ locking is
> being done. The simplest solution is to create the IPIs for all nodes
> at startup.
>
> Fixes: 7dcc37b3eff9 ("powerpc/xive: Map one IPI interrupt per node")
> Cc: stable@vger.kernel.org # v5.13
> Reported-by: Geetika Moolchandani <Geetika.Moolchandani1@ibm.com>
> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
>
> This patch breaks old versions of irqbalance (<= v1.4). Possible nodes
> are collected from /sys/devices/system/node/ but CPU-less nodes are
> not listed there. When interrupts are scanned, the link representing
> the node structure is NULL and segfault occurs.
This is an irqbalance regression due to :
https://github.com/Irqbalance/irqbalance/pull/172
I will report through an issue.
Anyhow, there is a better approach which is to allocate IPIs for all
nodes at boot time and do the mapping on demand. Removing the mapping
on last use seems more complex though.
I will send a v2 after some tests.
Thanks,
C.
> Version 1.7 seems immune.
>
> ---
> arch/powerpc/sysdev/xive/common.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
> index f3b16ed48b05..5d2c58dba57e 100644
> --- a/arch/powerpc/sysdev/xive/common.c
> +++ b/arch/powerpc/sysdev/xive/common.c
> @@ -1143,10 +1143,6 @@ static int __init xive_request_ipi(void)
> struct xive_ipi_desc *xid = &xive_ipis[node];
> struct xive_ipi_alloc_info info = { node };
>
> - /* Skip nodes without CPUs */
> - if (cpumask_empty(cpumask_of_node(node)))
> - continue;
> -
> /*
> * Map one IPI interrupt per node for all cpus of that node.
> * Since the HW interrupt number doesn't have any meaning,
>
prev parent reply other threads:[~2021-08-06 12:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-29 13:15 [PATCH] powerpc/xive: Do not skip CPU-less nodes when creating the IPIs Cédric Le Goater
2021-06-30 5:42 ` Srikar Dronamraju
2021-07-07 17:37 ` Laurent Vivier
2021-07-19 7:34 ` Laurent Vivier
2021-08-02 6:37 ` Michael Ellerman
2021-08-02 12:59 ` Cédric Le Goater
2021-08-06 11:50 ` Cédric Le Goater [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=481023b5-6857-1331-23cd-e9eabd511821@kaod.org \
--to=clg@kaod.org \
--cc=Geetika.Moolchandani1@ibm.com \
--cc=dgibson@redhat.com \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=lvivier@redhat.com \
--cc=srikar@linux.vnet.ibm.com \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).