From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH] printk/tracing: Do not trace printk_nmi_enter()
Date: Fri, 7 Sep 2018 23:52:21 +0900 [thread overview]
Message-ID: <20180907145221.GE482@tigerII.localdomain> (raw)
In-Reply-To: <20180907140342.GH24106@hirez.programming.kicks-ass.net>
On (09/07/18 16:03), Peter Zijlstra wrote:
> >
> > I would even argue that placing printk_nmi_enter() between
> > lockdep_off() and ftrace_nmi_enter() is wrong because if in the future
> > printk_nmi_enter() were to do any ftrace tracing, it wont be caught, as
> > it was by having it before lockdep_off().
> >
> > printk_nmi_enter() should not muck with IRQ state, nor should it do any
> > ftrace tracing. Since ftrace mucks with IRQ state when it gets enabled
> > or disabled, it will screw up lockdep, and lockdep will complain. That
> > way we can use lockdep not being off to catch this bug.
>
> The very bestest solution is to rm -rf printk ;-)
Talented, capable and tremendously clever people had spent decades on
making printk what it is today. I feel responsible for respecting that
effort and, thus, my vote would be to keep printk around for a while.
... we also support !CONFIG_PRINTK builds ;)
-ss
next prev parent reply other threads:[~2018-09-07 14:52 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-06 1:33 [PATCH] printk/tracing: Do not trace printk_nmi_enter() Steven Rostedt
2018-09-06 2:31 ` Sergey Senozhatsky
2018-09-06 9:04 ` Petr Mladek
2018-09-06 15:22 ` Steven Rostedt
2018-09-07 7:45 ` Peter Zijlstra
2018-09-07 8:28 ` Petr Mladek
2018-09-07 8:35 ` Sergey Senozhatsky
2018-09-07 13:47 ` Steven Rostedt
2018-09-07 9:30 ` Peter Zijlstra
2018-09-07 13:53 ` Steven Rostedt
2018-09-10 5:32 ` locking/lockdep: Fix NMI handling kbuild test robot
2018-09-07 7:34 ` [PATCH] printk/tracing: Do not trace printk_nmi_enter() Peter Zijlstra
2018-09-07 13:41 ` Steven Rostedt
2018-09-07 13:45 ` Peter Zijlstra
2018-09-07 13:55 ` Steven Rostedt
2018-09-07 14:01 ` Steven Rostedt
2018-09-07 14:03 ` Peter Zijlstra
2018-09-07 14:52 ` Sergey Senozhatsky [this message]
2018-09-07 14:02 ` Peter Zijlstra
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