Messages in this thread | | | Date | Wed, 10 Nov 2021 16:25:56 +0100 | From | Petr Mladek <> | Subject | Re: [PATCH] printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces |
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On Sun 2021-11-07 14:51:16, Nicholas Piggin wrote: > printk from NMI context relies on irq work being raised on the local CPU > to print to console. This can be a problem if the NMI was raised by a > lockup detector to print lockup stack and regs, because the CPU may not > enable irqs (because it is locked up). > > Introduce printk_trigger_flush() that can be called another CPU to try > to get those messages to the console, call that where printk_safe_flush > was previously called. > > --- a/arch/powerpc/kernel/watchdog.c > +++ b/arch/powerpc/kernel/watchdog.c > @@ -227,6 +227,12 @@ static void watchdog_smp_panic(int cpu) > cpumask_clear(&wd_smp_cpus_ipi); > }
The above context did not apply. I guess that it is a pending change that did not even reached linux-next yet.
The pushed code might be seen at https://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git/commit/?h=rework/printk_safe-removal&id=5d5e4522a7f404d1a96fd6c703989d32a9c9568d
> > + /* > + * Force flush any remote buffers that might be stuck in IRQ context > + * and therefore could not run their irq_work. > + */ > + printk_trigger_flush(); > + > if (hardlockup_panic) > nmi_panic(NULL, "Hard LOCKUP"); >
The patch has been committed into printk/linux.git, branch rework/printk_safe-removal.
I am going to add it into the pull request for 5.16-rc2 following week.
Best Regards, Petr
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