linux-kernel - [RFC PATCH 11/17] seq_buf: Move the seq

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Message-ID: <1431603304-162571-12-git-send-email-long.wanglong@huawei.com>
Date:	Thu, 14 May 2015 11:34:58 +0000
From:	Wang Long <long.wanglong@...wei.com>
To:	<rostedt@...dmis.org>, <jkosina@...e.cz>,
	<gregkh@...uxfoundation.org>
CC:	<stable@...r.kernel.org>, <wanglong@...qinren.net>,
	<peifeiyue@...wei.com>, <linux-kernel@...r.kernel.org>,
	<morgan.wang@...wei.com>, <paulmck@...ux.vnet.ibm.com>,
	<pmladek@...e.cz>, <dzickus@...hat.com>, <x86@...nel.org>,
	<sasha.levin@...cle.com>
Subject: [RFC PATCH 11/17] seq_buf: Move the seq_buf code to lib/

From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>

commit 8d58e99af5980d444948720977b0976455885391 upstream.

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

Tested-by: Jiri Kosina <jkosina@...e.cz>
Acked-by: Jiri Kosina <jkosina@...e.cz>
Reviewed-by: Petr Mladek <pmladek@...e.cz>
[wanglong: backport to 3.10 stable
- adjust context
]
Signed-off-by: Wang Long <long.wanglong@...wei.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/trace/Makefile           | 1 -
 lib/Makefile                    | 2 +-
 {kernel/trace => lib}/seq_buf.c | 0
 3 files changed, 1 insertion(+), 2 deletions(-)
 rename {kernel/trace => lib}/seq_buf.c (100%)

diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index cfb86f1..d7e2068 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -27,7 +27,6 @@ obj-$(CONFIG_RING_BUFFER_BENCHMARK) += ring_buffer_benchmark.o
 
 obj-$(CONFIG_TRACING) += trace.o
 obj-$(CONFIG_TRACING) += trace_output.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
diff --git a/lib/Makefile b/lib/Makefile
index 9efe480..4ecd2e4 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
diff --git a/kernel/trace/seq_buf.c b/lib/seq_buf.c
similarity index 100%
rename from kernel/trace/seq_buf.c
rename to lib/seq_buf.c
-- 
1.8.3.4

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