Re: [PATCH Dovetail 2/2] arm64: irq_pipeline: Fix the demotion checks for el0 and el1 IRQs
Florian Bezdeka <[email protected]>
| Newsgroups | dev.linux.lists.xenomai |
|---|---|
| Message-ID | <[email protected]> |
On Tue, 2026-02-17 at 09:00 +0100, Philippe Gerum wrote: > Florian Bezdeka <[email protected]> writes: > > > While reviewing some of the low level pipeline code I realized that > > the checks for task demotion are wrong on arm64. > > > > el0: The demotion check was missing in the oob case. We have to check > > for running_inband() only as user_mode(regs) will always be true. > > We are serving an IRQ over el0, so application / user mode. > > > > el1: The demotion check was unnecessary and "inactive" as > > user_mode(regs) is never true on el1, we are serving an IRQ over > > kernel mode. > > > > If the demotion happens from el1, you still want to check for a > rescheduling opportunity (i.e. kernel preemption case). > > > Signed-off-by: Florian Bezdeka <[email protected]> > > --- > > arch/arm64/kernel/entry-common.c | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c > > index 07fa70713ce04eaf3df9223354babcecde923280..9c99eb3d18c459a90e1f7ce4e4c307e235e457a2 100644 > > --- a/arch/arm64/kernel/entry-common.c > > +++ b/arch/arm64/kernel/entry-common.c > > @@ -73,6 +73,10 @@ static noinstr void arm64_pipeline_el0_irq(struct pt_regs *regs, > > do_interrupt_handler(regs, handler); > > /* Done, unwind now. */ > > handle_irq_pipelined_finish(prevd, regs); > > + if (running_inband()) { > > + stall_inband_nocheck(); > > + irqentry_exit_to_user_mode(regs); > > + } > > instrumentation_end(); > > arm64_exit_to_user_mode(regs); > > } > > @@ -90,10 +94,6 @@ static noinstr void arm64_pipeline_el1_irq(struct pt_regs *regs, > > prevd = handle_irq_pipelined_prepare(regs); > > do_interrupt_handler(regs, handler); > > handle_irq_pipelined_finish(prevd, regs); > > - if (running_inband() && user_mode(regs)) { > > - stall_inband_nocheck(); > > - irqentry_exit_to_user_mode(regs); > > - } > > instrumentation_end(); > > mte_check_tfsr_exit(); > > return; > > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c > index e0227d467cef4..770fc4059e083 100644 > --- a/arch/arm64/kernel/entry-common.c > +++ b/arch/arm64/kernel/entry-common.c > @@ -90,10 +90,8 @@ static noinstr void arm64_pipeline_el1_irq(struct pt_regs *regs, > prevd = handle_irq_pipelined_prepare(regs); > do_interrupt_handler(regs, handler); > handle_irq_pipelined_finish(prevd, regs); > - if (running_inband() && user_mode(regs)) { > - stall_inband_nocheck(); > - irqentry_exit_to_user_mode(regs); > - } > + if (running_inband()) > + goto out_irqentry; > instrumentation_end(); > mte_check_tfsr_exit(); > return; > @@ -109,6 +107,7 @@ static noinstr void arm64_pipeline_el1_irq(struct pt_regs *regs, > trace_hardirqs_on(); > unstall_inband_nocheck(); > handle_irq_pipelined_finish(prevd, regs); > +out_irqentry: > stall_inband_nocheck(); > trace_hardirqs_off(); > instrumentation_end(); > That would look a bit imbalanced. We would have one additional trace_hardirqs_off() and one irqentry_exit() call without counterparts. Is that really OK? Testing...