On 2025-02-13 08:25, Gabriele Monaco wrote:
On Thu, 2025-02-13 at 14:52 +0800, kernel test robot wrote:
kernel test robot noticed
"WARNING:at_kernel/workqueue.c:#__queue_delayed_work" on:
[ 2.640924][ T0] ------------[ cut here ]------------
[ 2.641646][ T0] WARNING: CPU: 0 PID: 0 at kernel/workqueue.c:2495
__queue_delayed_work (kernel/workqueue.c:2495 (discriminator 9))
[ 2.642874][ T0] Modules linked in:
[ 2.643381][ T0] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted
6.14.0-rc2-00002-g287adf9e9c1f #1
[ 2.644582][ T0] Hardware name: QEMU Standard PC (i440FX +
PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[ 2.645943][ T0] RIP: 0010:__queue_delayed_work
(kernel/workqueue.c:2495 (discriminator 9))
There seem to be major problems with this configuration, I'm trying to
understand what's wrong but, for the time being, this patchset is not
ready for inclusion.
I think there is an issue with the order of init functions at boot.
poking_init() calls mm_alloc(), which ends up calling mm_init().
The WARN_ON() is about a NULL wq pointer, which I suspect happens
if poking_init() is called before workqueue_init_early(), which
allocates system_wq.
Indeed, in start_kernel(), poking_init() is called before
workqueue_init_early().
I'm not sure what are the init order dependencies across subsystems here.
There is the following order in start_kernel():
[...]
mm_core_init();
poking_init();
ftrace_init();
/* trace_printk can be enabled here */
early_trace_init();
/*
* Set up the scheduler prior starting any interrupts (such as the
* timer interrupt). Full topology setup happens at smp_init()
* time - but meanwhile we still have a functioning scheduler.
*/
sched_init();
if (WARN(!irqs_disabled(),
"Interrupts were enabled *very* early, fixing it\n"))
local_irq_disable();
radix_tree_init();
maple_tree_init();
/*
* Set up housekeeping before setting up workqueues to allow the unbound
* workqueue to take non-housekeeping into account.
*/
housekeeping_init();
/*
* Allow workqueue creation and work item queueing/cancelling
* early. Work item execution depends on kthreads and starts after
* workqueue_init().
*/
workqueue_init_early();
[...]
So either we find a way to reorder this, or we make sure poking_init()
does not require the workqueue.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
