linux-kernel - Re: [RFC][PATCH 3/5 v2] seq_buf: Move the seq

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Date:	Fri, 27 Jun 2014 15:48:10 +0200
From:	Petr Mládek <pmladek@...e.cz>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Michal Hocko <mhocko@...e.cz>,
	Jan Kara <jack@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Dave Anderson <anderson@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Konstantin Khlebnikov <koct9i@...il.com>
Subject: Re: [RFC][PATCH 3/5 v2] seq_buf: Move the seq_buf code to lib/

On Thu 2014-06-26 17:49:04, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
> 
> The seq_buf functions are rather useful outside of tracing. Instead
> of having it be dependent on CONFIG_TRACING, move the code into lib/
> and allow other users to have access to it even when tracing is not
> configured.
> 
> The seq_buf utility is similar to the seq_file utility, but instead of
> writing sending data back up to userland, it writes it into a buffer
> defined at seq_buf_init(). This allows us to send a descriptor around
> that writes printf() formatted strings into it that can be retrieved
> later.
> 
> It is currently used by the tracing facility for such things like trace
> events to convert its binary saved data in the ring buffer into an
> ASCII human readable context to be displayed in /sys/kernel/debug/trace.
> 
> It can also be used for doing NMI prints safely from NMI context into
> the seq_buf and retrieved later and dumped to printk() safely. Doing
> printk() from an NMI context is dangerous because an NMI can preempt
> a current printk() and deadlock on it.
> 
> Link: http://lkml.kernel.org/p/20140619213952.058255809@goodmis.org
> 
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  kernel/trace/seq_buf.c | 348 -------------------------------------------------
>  lib/Makefile           |   2 +-
>  lib/seq_buf.c          | 348 +++++++++++++++++++++++++++++++++++++++++++++++++
>  lib/trace_seq.c        | 303 ++++++++++++++++++++++++++++++++++++++++++

I guess that lib/trace_seq.c was copied by mistake.

>  4 files changed, 652 insertions(+), 349 deletions(-)
>  delete mode 100644 kernel/trace/seq_buf.c
>  create mode 100644 lib/seq_buf.c
>  create mode 100644 lib/trace_seq.c
> 
> diff --git a/lib/Makefile b/lib/Makefile
> index ba967a19edba..6007194082c6 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
>  	 sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \
>  	 proportions.o flex_proportions.o prio_heap.o ratelimit.o show_mem.o \
>  	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
> -	 earlycpio.o
> +	 earlycpio.o seq_buf.o
>  
>  obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
>  lib-$(CONFIG_MMU) += ioremap.o

There is missing:

diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index edc98c72a634..67d6369ddf83 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -29,7 +29,6 @@ obj-$(CONFIG_RING_BUFFER_BENCHMARK) += ring_buffer_benchmark.o
 obj-$(CONFIG_TRACING) += trace.o
 obj-$(CONFIG_TRACING) += trace_output.o
 obj-$(CONFIG_TRACING) += trace_seq.o
-obj-$(CONFIG_TRACING) += seq_buf.o
 obj-$(CONFIG_TRACING) += trace_stat.o
 obj-$(CONFIG_TRACING) += trace_printk.o
 obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o


Best Regards,
Petr
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