Cédric Le Goater <c...@kaod.org> writes:
> 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: sta...@vger.kernel.org # v5.13
> Reported-by: Geetika Moolchandani <geetika.moolchanda...@ibm.com>
> Cc: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> Signed-off-by: Cédric Le Goater <c...@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.Breaking userspace is usually frowned upon, even if it is irqbalance. If CPU-less nodes appeared in /sys/devices/system/node would that fix it? Could we do that or is that not possible for other reasons? > Version 1.7 seems immune. Which was released in August 2020. Looks like some distros still ship 1.6, I take it you're not sure if that is broken or not. cheers
