Messages in this thread | | | From | Jann Horn <> | Date | Fri, 27 Mar 2020 04:05:43 +0100 | Subject | Re: [PATCH 0/2] Make printk_deferred() work properly before percpu setup is done |
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On Fri, Mar 27, 2020 at 3:45 AM Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> wrote: > On (20/03/26 17:32), Jann Horn wrote: > > While I was doing some development work, I noticed that if you call > > printk_deferred() before percpu setup has finished, stuff breaks, and > > e.g. "dmesg -w" fails to print new messages. > > > > This happens because writing to percpu memory before percpu > > initialization is done causes the modified percpu memory to be > > propagated from the boot CPU to all the secondary CPUs; and both the > > printk code as well as the irq_work implementation use percpu memory. > > > > I think that printk_deferred() ought to work even before percpu > > initialization, since it is used by things like pr_warn_ratelimited() > > and the unwinder infrastructure. I'm not entirely sure though whether > > this is the best way to implement that, or whether it would be better to > > let printk_deferred() do something different if it is called during > > early boot. > > Hi Jann, > > I believe we have a patch for this issue > > https://lore.kernel.org/lkml/20200303113002.63089-1-sergey.senozhatsky@gmail.com/
Ah, thanks, I didn't think of searching the list archives for an existing pending patch...
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