Messages in this thread | | | From | John Ogness <> | Subject | Re: Removal of printk safe buffers delays NMI context printk | Date | Fri, 05 Nov 2021 15:03:27 +0106 |
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On 2021-11-05, Nicholas Piggin <npiggin@gmail.com> wrote: >> What was removed from 93d102f094b was irq_work triggering on all >> CPUs. > > No, it was the caller executing the flush for all remote CPUs itself. > irq work was not involved (and irq work can't be raised in a remote > CPU from NMI context).
Maybe I am missing something. In 93d102f094b~1 I see:
watchdog_smp_panic printk_safe_flush __printk_safe_flush printk_safe_flush_buffer printk_safe_flush_line printk_deferred vprintk_deferred vprintk_emit (but no direct printing) defer_console_output irq_work_queue
AFAICT, using defer_console_output() instead of your new printk_flush() should cause the exact behavior as before.
> but we do need that printk flush capability back there and for > nmi_backtrace.
Agreed. I had not considered this necessary side-effect when I removed the NMI safe buffers.
I am just wondering if we should fix the regression by going back to using irq_work (such as defer_console_output()) or if we want to introduce something new that introduces direct printing.
John Ogness
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