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From: "Petr Mládek" <pmladek@suse.cz>
To: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Jiri Kosina <jkosina@suse.cz>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.cz>, Jan Kara <jack@suse.cz>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Dave Anderson <anderson@redhat.com>
Subject: Re: [RFC][PATCH 0/3] x86/nmi: Print all cpu stacks from NMI safely
Date: Wed, 25 Jun 2014 13:57:45 +0200	[thread overview]
Message-ID: <20140625115745.GK8769@pathway.suse.cz> (raw)
In-Reply-To: <CALYGNiOT9XkiE1Q=AimOt42UkQ430Qy89cseNLVaMf96O9=FJw@mail.gmail.com>

On Wed 2014-06-25 15:04:41, Konstantin Khlebnikov wrote:
> On Wed, Jun 25, 2014 at 2:01 PM, Jiri Kosina <jkosina@suse.cz> wrote:
> > On Tue, 24 Jun 2014, Konstantin Khlebnikov wrote:
> 
> I like that context-depend printk routing from this patchset.
> I'm just not quite happy with this straight forward implementation.
> Rerouting flow into different buffers might serve different purposes,
> it must make code simpler instead of adding yet another knot.
> For example printk continuation might use it too.

Note that we could not share the buffer between normal and NMI
context easily. We would end with the same locking problems as we have now.

In fact, any sharing is complicated when NMI is involved, especially
when we need to access the data from both NMI and normal context.
And we need to copy them into the main ring buffer in a normal context.

This patchset works only because arch_trigger_all_cpu_backtrace() is
called from normal context. Also all other calls are ignored until the
previous call is finished, see "backtrace_flag".


Best Regards,
Petr

  reply	other threads:[~2014-06-25 11:57 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-19 21:33 [RFC][PATCH 0/3] x86/nmi: Print all cpu stacks from NMI safely Steven Rostedt
2014-06-19 21:33 ` [RFC][PATCH 1/3] trace_seq: Move the trace_seq code to lib/ Steven Rostedt
2014-06-20  4:45   ` Linus Torvalds
2014-06-20 16:21     ` Steven Rostedt
2014-06-20  5:06   ` Andrew Morton
2014-06-20 16:58     ` Steven Rostedt
2014-06-20 17:12       ` Andrew Morton
2014-06-20 17:17         ` Steven Rostedt
2014-06-20 20:28         ` Steven Rostedt
2014-06-20 20:51           ` Steven Rostedt
2014-06-23 16:33             ` Petr Mládek
2014-06-23 17:03               ` Steven Rostedt
2014-06-22  7:38       ` Johannes Berg
2014-06-23 16:08         ` Steven Rostedt
2014-06-23 17:38           ` Johannes Berg
2014-06-23 18:04             ` Steven Rostedt
2014-06-24  8:19               ` Johannes Berg
2014-06-19 21:33 ` [RFC][PATCH 2/3] printk: Add per_cpu printk func to allow printk to be diverted Steven Rostedt
2014-06-23 16:06   ` Paul E. McKenney
2014-06-19 21:33 ` [RFC][PATCH 3/3] x86/nmi: Perform a safe NMI stack trace on all CPUs Steven Rostedt
2014-06-20 13:58   ` Don Zickus
2014-06-20 14:21     ` Steven Rostedt
2014-06-20 14:55   ` Petr Mládek
2014-06-20 15:17     ` Steven Rostedt
2014-06-23 16:12   ` Paul E. McKenney
2014-06-19 21:56 ` [RFC][PATCH 0/3] x86/nmi: Print all cpu stacks from NMI safely Jiri Kosina
2014-06-19 22:58   ` Steven Rostedt
2014-06-19 23:03     ` Jiri Kosina
2014-06-19 23:19       ` Steven Rostedt
2014-06-19 23:27         ` Jiri Kosina
2014-06-19 23:36           ` Steven Rostedt
2014-06-19 23:38             ` Jiri Kosina
2014-06-20 14:35               ` Petr Mládek
2014-06-24 13:32                 ` Konstantin Khlebnikov
2014-06-25 10:01                   ` Jiri Kosina
2014-06-25 11:04                     ` Konstantin Khlebnikov
2014-06-25 11:57                       ` Petr Mládek [this message]
2014-06-25 12:21                   ` Petr Mládek

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