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Message-ID: <YFbY8kF7ilYoxvYp@google.com>
Date: Sun, 21 Mar 2021 14:26:10 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: John Ogness <john.ogness@...utronix.de>
Cc: Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Eric Biederman <ebiederm@...ssion.com>,
Nicholas Piggin <npiggin@...il.com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Alistair Popple <alistair@...ple.id.au>,
Jordan Niethe <jniethe5@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
Cédric Le Goater <clg@...d.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>, Yue Hu <huyue2@...ong.com>,
Alexey Kardashevskiy <aik@...abs.ru>,
Rafael Aquini <aquini@...hat.com>,
Tiezhu Yang <yangtiezhu@...ngson.cn>,
"Guilherme G. Piccoli" <gpiccoli@...onical.com>,
"Paul E. McKenney" <paulmck@...nel.org>,
linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org
Subject: Re: [PATCH next v1 2/3] printk: remove safe buffers
On (21/03/17 00:33), John Ogness wrote:
[..]
> void printk_nmi_direct_enter(void)
> {
> @@ -324,27 +44,8 @@ void printk_nmi_direct_exit(void)
> this_cpu_and(printk_context, ~PRINTK_NMI_DIRECT_CONTEXT_MASK);
> }
>
> -#else
> -
> -static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
> -{
> - return 0;
> -}
> -
> #endif /* CONFIG_PRINTK_NMI */
>
> -/*
> - * Lock-less printk(), to avoid deadlocks should the printk() recurse
> - * into itself. It uses a per-CPU buffer to store the message, just like
> - * NMI.
> - */
> -static __printf(1, 0) int vprintk_safe(const char *fmt, va_list args)
> -{
> - struct printk_safe_seq_buf *s = this_cpu_ptr(&safe_print_seq);
> -
> - return printk_safe_log_store(s, fmt, args);
> -}
> -
> /* Can be preempted by NMI. */
> void __printk_safe_enter(void)
> {
> @@ -369,7 +70,10 @@ __printf(1, 0) int vprintk_func(const char *fmt, va_list args)
> * Use the main logbuf even in NMI. But avoid calling console
> * drivers that might have their own locks.
> */
> - if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK)) {
> + if (this_cpu_read(printk_context) &
> + (PRINTK_NMI_DIRECT_CONTEXT_MASK |
> + PRINTK_NMI_CONTEXT_MASK |
> + PRINTK_SAFE_CONTEXT_MASK)) {
Do we need printk_nmi_direct_enter/exit() and PRINTK_NMI_DIRECT_CONTEXT_MASK?
Seems like all printk_safe() paths are now DIRECT - we store messages to the
prb, but don't call console drivers.
-ss
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