linux-kernel - [linux-next, x86_64] no backtrace after "printk/nmi: generic solution for safe printk in NMI"

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Date:	Thu, 25 Feb 2016 18:46:21 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Jan Kara <jack@...e.cz>, Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [linux-next, x86_64] no backtrace after "printk/nmi: generic
 solution for safe printk in NMI"

Hello Petr,

seem that commit b927968830676373caf4241e80d8b447133f84b2
	Author: Petr Mladek <pmladek@...e.com>
	Date:   Thu Feb 25 13:00:35 2016 +1100

	    printk/nmi: generic solution for safe printk in NMI
    
	    printk() takes some locks and could not be used a safe way in NMI context.
    
	    The chance of a deadlock is real especially when printing stacks from all
	    CPUs.  This particular problem has been addressed on x86 by the commit
	    a9edc8809328 ("x86/nmi: Perform a safe NMI stack trace on all CPUs").
    
	    The patchset brings two big advantages.  First, it makes the NMI
	    backtraces safe on all architectures for free.  Second, it makes all NMI
	    messages almost safe on all architectures (the temporary buffer is
	    limited.  We still should keep the number of messages in NMI context at
	    minimum).
	[..]


makes my x86_64 boxen unhappy, I see no CPU backtraces and no panic messages
on HARDLOCKUPs (CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE=1).

does it work for you?

	-ss