On Fri, 20 Jun 2014 09:58:15 -0400 Don Zickus <[email protected]> wrote:
> On Thu, Jun 19, 2014 at 05:33:32PM -0400, Steven Rostedt wrote: > > From: "Steven Rostedt (Red Hat)" <[email protected]> > > > > When trigger_all_cpu_backtrace() is called on x86, it will trigger an > > NMI on each CPU and call show_regs(). But this can lead to a hard lock > > up if the NMI comes in on another printk(). > > > > In order to avoid this, when the NMI triggers, it switches the printk > > routine for that CPU to call a NMI safe printk function that records the > > printk in a per_cpu trace_seq descriptor. After all NMIs have finished > > recording its data, the trace_seqs are printed in a safe context. > > Ah, if there is other places that need to call a printk from an NMI > context, do we have to copy and paste this code there too? That would > seem a little much. :-) I guess my only concern really is the seq_init > and seq print stuff. The handler seems relatively simple. This is a special case for printing from NMI. As you can trigger it with sysrq-l. But any other prints from NMI should only be in the BUG() case, where we should just force the output and override any locks in printk. > > Can we isolate this to a pr_nmi() routine or something? Or maybe a > pr_nmi_queue and pr_nmi_dump or something? > We'll have to see how traction this gets. It's just an RFC. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
