Re: [PATCH] irqchip: gic-v3-its: irq_pipeline: Fix OOB context in-band lock warning for ITS lock

On Fri, 2026-07-10 at 12:12 +0200, Jan Kiszka wrote:
> On 25.06.26 11:32, linz wrote:
> > Hi, I find a call trace when I use v6.6.y-dovetail + xenomai v3.3 branch, the call trace is as follows
> > 
> > [    1.510903] IRQ pipeline: some code running in oob context 'Xenomai'
> >                              called an in-band only routine
> > [    1.510912] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G S                 6.6.63-dovetail2 #8
> > [    1.510918] Hardware name: Pe2204 DEMO DDR4 (DT)
> > [    1.510920] IRQ stage: Xenomai
> > [    1.510923] Call trace:
> > [    1.510926]  dump_backtrace+0x90/0xe4
> > [    1.510940]  show_stack+0x14/0x1c
> > [    1.510946]  dump_stack_lvl+0x84/0xc8
> > [    1.510953]  dump_stack+0x14/0x1c
> > [    1.510957]  check_inband_stage+0xb0/0xc8
> > [    1.510965]  inband_irq_save+0xc/0x28
> > [    1.510971]  _raw_spin_lock_irqsave+0x14/0x90
> > [    1.510977]  its_send_single_command+0x24/0x154
> > [    1.510984]  lpi_update_config+0x9c/0x144
> > [    1.510990]  its_mask_irq+0x2c/0x64
> > [    1.510997]  irq_chip_mask_parent+0x18/0x20
> > [    1.511005]  its_mask_msi_irq+0x1c/0x28
> > [    1.511012]  handle_fasteoi_irq+0x1cc/0x2b4
> > [    1.511016]  generic_pipeline_irq_desc+0x6c/0xa4
> > [    1.511021]  generic_handle_domain_irq+0x18/0x20
> > [    1.511028]  gic_handle_irq+0x4c/0x120
> > [    1.511032]  handle_irq_pipelined+0x40/0x64
> > [    1.511038]  call_on_irq_stack+0x24/0x30
> > [    1.511044]  do_interrupt_handler+0x138/0x158
> > [    1.511050]  el1_interrupt+0x40/0x110
> > [    1.511055]  el1h_64_irq_handler+0x14/0x1c
> > [    1.511061]  el1h_64_irq+0x64/0x68
> > [    1.511064]  default_idle_call+0x30/0x78
> > [    1.511071]  do_idle+0x128/0x150
> > [    1.511077]  cpu_startup_entry+0x34/0x38
> > [    1.511081]  kernel_init+0x0/0x1d4
> > [    1.511088]  arch_post_acpi_subsys_init+0x0/0x8
> > [    1.511096]  start_kernel+0x504/0x5cc
> > [    1.511103]  __primary_switched+0xbc/0xc4
> > 
> > 
> > The function call causing the issue is as follows:
> > generic_handle_domain_irq
> >     => generic_pipeline_irq_desc
> >         => generic_handle_irq_desc
> >             => handle_fasteoi_irq
> >                 => mask_cond_eoi_irq
> >                     => mask_irq
> >                         => its_mask_msi_irq
> >                             => irq_chip_mask_parent
> >                                 => its_mask_irq
> >                                     => lpi_update_config
> >                                         => its_send_inv
> >                                             => BUILD_SINGLE_CMD_FUNC
> >                                                 => raw_spin_lock_irqsave(&its->lock, flags);
> > 
> > 
> > On Dovetail-enabled kernels with Xenomai IRQ pipeline, GICv3 ITS interrupt handling runs in OOB (out-of-band) interrupt context. The original raw_spinlock_t used for its_node->lock invokes the standard in-band-only raw_spin_lock_irqsave() interface.
> > This triggers the following pipeline context violation warning: IRQ pipeline: some code running in oob context 'Xenomai' called an in-band only routine
> > 
> > raw_spin_lock_irqsave() is an in-band exclusive API and cannot be safely called from Xenomai OOB interrupt context, which violates the IRQ pipeline isolation rules.
> > 
> > I think that fix this by replacing raw_spinlock_t with hybrid_spinlock_t for the ITS node lock. The hybrid spinlock supports both in-band Linux kernel context and OOB Xenomai pipeline context, adapting lock/irqsave logic dynamically according to the running context, eliminating the context mismatch warning while guaranteeing lock mutual exclusion.
> > 
> > The fixed up patch is as follows:
> > 
> > From 1037fcf6d75ecf37e1caf283d1198177e7410be3 Mon Sep 17 00:00:00 2001
> > From: zhanglin <[email protected]>
> > Date: Thu, 25 Jun 2026 16:56:31 +0800
> > Subject: [PATCH] irqchip: gic-v3-its: irq_pipeline: fix OOB context in-band
> >  lock warning for ITS lock
> > 
> > ---
> >  drivers/irqchip/irq-gic-v3-its.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> > index 0e57735eac..847b008b71 100644
> > --- a/drivers/irqchip/irq-gic-v3-its.c
> > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > @@ -94,7 +94,7 @@ struct its_device;
> >   * list.
> >   */
> >  struct its_node {
> > -    raw_spinlock_t        lock;
> > +    hybrid_spinlock_t     lock;
> >      struct mutex        dev_alloc_lock;
> >      struct list_head    entry;
> >      void __iomem        *base;
> > -- 
> > 2.34.1
> > 
> > Please help to review it, thank you.
> 
> Thanks for reporting.
> 
> Philippe, Florian, any comments on this?
> 
> Jan

hybrid_spinlock_t doesn't look right at first glance, it's use should be
limited to struct irq_desc and IRQ chips. I would have expected
hard_spinlock_t, but I might miss something.

Assuming the gic-v3 IRQ chip is already marked / flagged as
IRQCHIP_PIPELINE_SAFE, right?

Florian