Re: [External] [patch 0/4] genirq: Prevent migration live lock in handle_edge_irq()

[Liangyan <liangyan.peng@bytedance.com>]

On 2025/7/19 02:54, Thomas Gleixner wrote:
> Yicon reported and Liangyan debugged a live lock in handle_edge_irq()
> related to interrupt migration.
> 
> If the interrupt affinity is moved to a new target CPU and the interrupt is
> currently handled on the previous target CPU for edge type interrupts the
> handler might get stuck on the previous target:
> 
> CPU 0 (previous target)		CPU 1 (new target)
> 
>   handle_edge_irq()
>    repeat:
> 	handle_event()		handle_edge_irq()
> 			        if (INPROGESS) {
> 				  set(PENDING);
> 				  mask();
> 				  return;
> 				}
> 	if (PENDING) {
> 	  clear(PENDING);
> 	  unmask();
> 	  goto repeat;
> 	}
> 
> The migration in software never completes and CPU0 continues to handle the
> pending events forever. This happens when the device raises interrupts with
> a high rate and always before handle_event() completes and before the CPU0
> handler can clear INPROGRESS so that CPU1 sets the PENDING flag over and
> over. This has been observed in virtual machines.
> 
> The following series is addressing this by making the new target CPU wait
> for the handler to complete on CPU1 and thereby completing the software
> migration.
> 
> A draft combo patch of this has been tested by Liangyan:
> 
>   https://lore.kernel.org/all/87o6u0rpaa.ffs@tglx
> 
> The series splits up the draft patch and has proper changelogs.
> 
> Thanks,
> 
> 	tglx
> ---
>  chip.c      |   68 ++++++++++++++++++++++++++++++++++++++++++++++++++++--------
>  internals.h |    6 ++---
>  pm.c        |   16 +++++---------
>  spurious.c  |   37 --------------------------------
>  4 files changed, 69 insertions(+), 58 deletions(-)
> 
> 

Tested-by: Liangyan <liangyan.peng@bytedance.com>

Regards,
Liangyan