From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Date: Tue, 27 Jul 2021 09:26:54 +0200 From: Petr Mladek Subject: Re: [PATCH printk v4 0/6] printk: remove safe buffers Message-ID: References: <20210715193359.25946-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210715193359.25946-1-john.ogness@linutronix.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: John Ogness Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, "Paul E. McKenney" , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Eric Biederman , Nicholas Piggin , Christophe Leroy , =?iso-8859-1?Q?C=E9dric?= Le Goater , Andrew Morton , Kees Cook , Tiezhu Yang , Alexey Kardashevskiy , Yue Hu , linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org, Russell King , Ingo Molnar , Marc Zyngier , Valentin Schneider , Geert Uytterhoeven , Mike Rapoport , "Wolfram Sang (Renesas)" , Anshuman Khandual , Xiongwei Song , Frederic Weisbecker , Peter Zijlstra , Masahiro Yamada , Nathan Chancellor , Nick Desaulniers , Nick Terrell , Vipin Sharma , Rasmus Villemoes , Daniel Borkmann , Vlastimil Babka , linux-arm-kernel@lists.infradead.org On Thu 2021-07-15 21:39:53, John Ogness wrote: > 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.) > > 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 The entire patchset has been committed into printk/linux.git, branch rework/printk_safe-removal. Note that I have updated the 4th patch as discussed, see https://lore.kernel.org/r/20210721120026.y3dqno24ahw4sazy@pathway.suse.cz https://lore.kernel.org/r/20210721130852.zrjnti6b3fwjgdzj@pathway.suse.cz Best Regards, Petr _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec