From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: "Alexey Kardashevskiy" <aik@ozlabs.ru>,
"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
"Wolfram Sang (Renesas)" <wsa+renesas@sang-engineering.com>,
"Paul Mackerras" <paulus@samba.org>,
"Tiezhu Yang" <yangtiezhu@loongson.cn>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Marc Zyngier" <maz@kernel.org>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Russell King" <linux@armlinux.org.uk>,
"Peter Zijlstra" <peterz@infradead.org>,
"Yue Hu" <huyue2@yulong.com>, "Ingo Molnar" <mingo@redhat.com>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
linux-arm-kernel@lists.infradead.org,
"Valentin Schneider" <valentin.schneider@arm.com>,
"Kees Cook" <keescook@chromium.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Anshuman Khandual" <anshuman.khandual@arm.com>,
"Vipin Sharma" <vipinsh@google.com>,
"Frederic Weisbecker" <frederic@kernel.org>,
"Nicholas Piggin" <npiggin@gmail.com>,
"Nathan Chancellor" <nathan@kernel.org>,
"Nick Terrell" <terrelln@fb.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Xiongwei Song" <sxwjean@gmail.com>,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
"Sergey Senozhatsky" <senozhatsky@chromium.org>,
"Eric Biederman" <ebiederm@xmission.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org, "Mike Rapoport" <rppt@kernel.org>,
"Cédric Le Goater" <clg@kaod.org>
Subject: [PATCH printk v4 0/6] printk: remove safe buffers
Date: Thu, 15 Jul 2021 21:39:53 +0206 [thread overview]
Message-ID: <20210715193359.25946-1-john.ogness@linutronix.de> (raw)
Hi,
Here is v4 of a series to remove the safe buffers. v3 can be
found here [0]. The safe buffers are no longer needed because
messages can be stored directly into the log buffer from any
context.
However, the safe buffers also provided a form of recursion
protection. For that reason, explicit recursion protection is
implemented for this series.
The safe buffers also implicitly provided serialization
between multiple CPUs executing in NMI context. This was
particularly necessary for the nmi_backtrace() output. This
serializiation is now preserved by using the printk cpulock.
With the removal of the safe buffers, there is no need for
extra NMI enter/exit tracking. So this is also removed
(which includes removing the config option CONFIG_PRINTK_NMI).
And finally, there are a few places in the kernel that need to
specify code blocks where all printk calls are to be deferred
printing. Previously the NMI tracking API was being (mis)used
for this purpose. This series introduces an official and
explicit interface for such cases. (Note that all deferred
printing will be removed anyway, once printing kthreads are
introduced.)
Changes since v3:
- Remove safe context tracking in vprintk().
- Add safe context tracking for @console_owner usage since that
is also a component of the printing code.
- Refactor syslog_print() so that it is easier to understand
and follow the locking logic.
- Introduce printk_deferred_enter/exit functions to be used by
code that needs to specify code block where all printk calls
are to be deferred printing.
John Ogness
[0] https://lore.kernel.org/lkml/20210624111148.5190-1-john.ogness@linutronix.de
John Ogness (6):
lib/nmi_backtrace: explicitly serialize banner and regs
printk: track/limit recursion
printk: remove safe buffers
printk: remove NMI tracking
printk: convert @syslog_lock to mutex
printk: syslog: close window between wait and read
arch/arm/kernel/smp.c | 4 +-
arch/powerpc/kernel/traps.c | 1 -
arch/powerpc/kernel/watchdog.c | 5 -
arch/powerpc/kexec/crash.c | 2 +-
include/linux/hardirq.h | 2 -
include/linux/printk.h | 41 ++--
init/Kconfig | 5 -
kernel/kexec_core.c | 1 -
kernel/panic.c | 3 -
kernel/printk/internal.h | 25 ---
kernel/printk/printk.c | 268 ++++++++++++++----------
kernel/printk/printk_safe.c | 364 +--------------------------------
kernel/trace/trace.c | 4 +-
lib/nmi_backtrace.c | 13 +-
14 files changed, 194 insertions(+), 544 deletions(-)
base-commit: 70333dec446292cd896cd051d2ebd6808b328949
--
2.20.1
next reply other threads:[~2021-07-15 19:34 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 19:33 John Ogness [this message]
2021-07-15 19:33 ` [PATCH printk v4 3/6] printk: remove safe buffers John Ogness
2021-07-21 11:25 ` Petr Mladek
2021-09-02 16:48 ` Geert Uytterhoeven
2021-07-15 19:33 ` [PATCH printk v4 4/6] printk: remove NMI tracking John Ogness
2021-07-21 12:00 ` Petr Mladek
2021-07-21 12:46 ` John Ogness
2021-07-21 13:08 ` Petr Mladek
2021-07-21 13:23 ` John Ogness
2021-07-27 7:26 ` [PATCH printk v4 0/6] printk: remove safe buffers Petr Mladek
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