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Message-ID: <20190816055416.GA4460@dhcp-128-65.nay.redhat.com>
Date: Fri, 16 Aug 2019 13:54:16 +0800
From: Dave Young <dyoung@...hat.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
Petr Mladek <pmladek@...e.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andrea Parri <andrea.parri@...rulasolutions.com>,
Thomas Gleixner <tglx@...utronix.de>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Brendan Higgins <brendanhiggins@...gle.com>,
kexec@...ts.infradead.org, Simon Horman <horms@...ge.net.au>,
Kazuhito Hagio <k-hagio@...jp.nec.com>,
David Woodhouse <dwmw2@...radead.org>
Subject: Re: [RFC PATCH v4 9/9] printk: use a new ringbuffer implementation
On 08/16/19 at 01:46pm, Dave Young wrote:
> John, can you cc kexec list for your later series?
>
> On 08/08/19 at 12:32am, John Ogness wrote:
> > This is a major change because the API (and underlying workings)
> > of the new ringbuffer are completely different than the previous
> > ringbuffer. Since there are several components of the printk
> > infrastructure that use the ringbuffer API (console, /dev/kmsg,
> > syslog, kmsg_dump), there are quite a few changes throughout the
> > printk implementation.
> >
> > This is also a conservative change because it continues to use the
> > logbuf_lock raw spinlock even though the new ringbuffer is lockless.
> >
> > The externally visible changes are:
> >
> > 1. The exported vmcore info has changed:
> >
> > - VMCOREINFO_SYMBOL(log_buf);
> > - VMCOREINFO_SYMBOL(log_buf_len);
> > - VMCOREINFO_SYMBOL(log_first_idx);
> > - VMCOREINFO_SYMBOL(clear_idx);
> > - VMCOREINFO_SYMBOL(log_next_idx);
> > + VMCOREINFO_SYMBOL(printk_rb_static);
> > + VMCOREINFO_SYMBOL(printk_rb_dynamic);
>
> I assumed this needs some userspace work in kexec, how did you test
> them?
>
> makedumpfile should need changes to dump the kernel log.
>
> Also kexec-tools includes a vmcore-dmesg.c to extrace dmesg from
> /proc/vmcore.
>
> >
> > 2. For the CONFIG_PPC_POWERNV powerpc platform, kernel log buffer
> > registration is no longer available because there is no longer
> > a single contigous block of memory to represent all of the
> > ringbuffer.
> >
> > Signed-off-by: John Ogness <john.ogness@...utronix.de>
> > ---
> > arch/powerpc/platforms/powernv/opal.c | 22 +-
> > include/linux/kmsg_dump.h | 6 +-
> > include/linux/printk.h | 12 -
> > kernel/printk/printk.c | 745 ++++++++++++++------------
> > kernel/printk/ringbuffer.h | 24 +
> > 5 files changed, 415 insertions(+), 394 deletions(-)
> >
[snip]
Seems kexec list has 40k limitation for msg body. Simon and David, maybe it is
too small?
Thanks
Dave
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