On Fri, 9 May 2014, Petr Mladek wrote: > printk() cannot be used safely in NMI context because it uses internal locks > and thus could cause a deadlock. Unfortunately there are circumstances when > calling printk from NMI is very useful. For example, all WARN.*(in_nmi()) > would be much more helpful if they didn't lockup the machine. > > Another example would be arch_trigger_all_cpu_backtrace for x86 which uses NMI > to dump traces on all CPU (either triggered by sysrq+l or from RCU stall > detector).
I am rather surprised that this patchset hasn't received a single review comment for 3 weeks. Let me point out that the issues Petr is talking about in the cover letter are real -- we've actually seen the lockups triggered by RCU stall detector trying to dump stacks on all CPUs, and hard-locking machine up while doing so. So this really needs to be solved. -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
