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From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Petr Mladek <pmladek@suse.com>
Cc: John Ogness <john.ogness@linutronix.de>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org,
	Michael Ellerman <mpe@ellerman.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Eric Biederman <ebiederm@xmission.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Nicholas Piggin <npiggin@gmail.com>,
	Alistair Popple <alistair@popple.id.au>,
	Jordan Niethe <jniethe5@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Kees Cook <keescook@chromium.org>,
	Tiezhu Yang <yangtiezhu@loongson.cn>,
	Alexey Kardashevskiy <aik@ozlabs.ru>, Yue Hu <huyue2@yulong.com>,
	Rafael Aquini <aquini@redhat.com>,
	"Guilherme G. Piccoli" <gpiccoli@canonical.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org
Subject: Re: [PATCH printk v2 2/5] printk: remove safe buffers
Date: Fri, 2 Apr 2021 11:14:18 +0900	[thread overview]
Message-ID: <YGZ9+kfQKxASmVDR@google.com> (raw)
In-Reply-To: <YGXV8LJarjUJDhvy@alley>

On (21/04/01 16:17), Petr Mladek wrote:
> > For the long term, we should introduce a printk-context API that allows
> > callers to perfectly pack their multi-line output into a single
> > entry. We discussed [0][1] this back in August 2020.
> 
> We need a "short" term solution. There are currently 3 solutions:
> 
> 1. Keep nmi_safe() and all the hacks around.
> 
> 2. Serialize nmi_cpu_backtrace() by a spin lock and later by
>    the special lock used also by atomic consoles.
> 
> 3. Tell complaining people how to sort the messed logs.

Are we talking about nmi_cpu_backtrace()->dump_stack() or some
other path?

dump_stack() seems to be already serialized by `dump_lock`. Hmm,
show_regs() is not serialized, seems like it should be under the
same `dump_lock` as dump_stack().

WARNING: multiple messages have this Message-ID
From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Paul Mackerras <paulus@samba.org>,
	Tiezhu Yang <yangtiezhu@loongson.cn>,
	Rafael Aquini <aquini@redhat.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	Alexey Kardashevskiy <aik@ozlabs.ru>, Yue Hu <huyue2@yulong.com>,
	Jordan Niethe <jniethe5@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	John Ogness <john.ogness@linutronix.de>,
	Alistair Popple <alistair@popple.id.au>,
	"Guilherme G. Piccoli" <gpiccoli@canonical.com>,
	Nicholas Piggin <npiggin@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH printk v2 2/5] printk: remove safe buffers
Date: Fri, 2 Apr 2021 11:14:18 +0900	[thread overview]
Message-ID: <YGZ9+kfQKxASmVDR@google.com> (raw)
In-Reply-To: <YGXV8LJarjUJDhvy@alley>

On (21/04/01 16:17), Petr Mladek wrote:
> > For the long term, we should introduce a printk-context API that allows
> > callers to perfectly pack their multi-line output into a single
> > entry. We discussed [0][1] this back in August 2020.
> 
> We need a "short" term solution. There are currently 3 solutions:
> 
> 1. Keep nmi_safe() and all the hacks around.
> 
> 2. Serialize nmi_cpu_backtrace() by a spin lock and later by
>    the special lock used also by atomic consoles.
> 
> 3. Tell complaining people how to sort the messed logs.

Are we talking about nmi_cpu_backtrace()->dump_stack() or some
other path?

dump_stack() seems to be already serialized by `dump_lock`. Hmm,
show_regs() is not serialized, seems like it should be under the
same `dump_lock` as dump_stack().

  reply	other threads:[~2021-04-02  2:14 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-30 15:35 [PATCH printk v2 0/5] " John Ogness
2021-03-30 15:35 ` John Ogness
2021-03-30 15:35 ` John Ogness
2021-03-30 15:35 ` [PATCH printk v2 1/5] printk: track/limit recursion John Ogness
2021-04-01 10:00   ` Petr Mladek
2021-04-02  2:03     ` Sergey Senozhatsky
2021-03-30 15:35 ` [PATCH printk v2 2/5] printk: remove safe buffers John Ogness
2021-03-30 15:35   ` John Ogness
2021-03-31  7:59   ` John Ogness
2021-03-31  7:59     ` John Ogness
2021-04-01 12:21   ` Petr Mladek
2021-04-01 12:21     ` Petr Mladek
2021-04-01 13:19     ` John Ogness
2021-04-01 13:19       ` John Ogness
2021-04-01 14:17       ` Petr Mladek
2021-04-01 14:17         ` Petr Mladek
2021-04-02  2:14         ` Sergey Senozhatsky [this message]
2021-04-02  2:14           ` Sergey Senozhatsky
2021-04-06 11:17           ` Petr Mladek
2021-04-06 11:17             ` Petr Mladek
2021-04-06 11:01         ` John Ogness
2021-04-06 11:01           ` John Ogness
2021-03-30 15:35 ` [PATCH printk v2 3/5] printk: remove NMI tracking John Ogness
2021-03-30 15:35   ` John Ogness
2021-03-30 15:35   ` John Ogness
2021-04-01 14:37   ` Petr Mladek
2021-04-01 14:37     ` Petr Mladek
2021-04-01 14:37     ` Petr Mladek
2021-03-30 15:35 ` [PATCH printk v2 4/5] printk: convert @syslog_lock to mutex John Ogness
2021-04-01 15:13   ` Petr Mladek
2021-03-30 15:35 ` [PATCH printk v2 5/5] printk: syslog: close window between wait and read John Ogness

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