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Date: Thu, 21 Jun 2012 13:01:38 -0700
From: Joe Perches <joe@...ches.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ingo Molnar <mingo@...nel.org>,
Fengguang Wu <fengguang.wu@...el.com>,
LKML <linux-kernel@...r.kernel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"kay.sievers" <kay.sievers@...y.org>,
"Paul E. McKenney" <paulmck@...ibm.com>,
Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [RFC PATCH] printk: Enable/disable buffering and add printk_flush()
Add functions to enable/disable printk buffering.
Add a function to force any buffered output to be emitted.
printk_flush() also emits "printk_flush\n" at KERN_DEFAULT.
---
Perhaps something like this instead of just the one printk_flush()?
Doesn't require any additional KERN_LEVEL '<f>' addition.
Compiled but completely untested...
include/linux/printk.h | 18 ++++++++++++++++++
kernel/printk.c | 36 ++++++++++++++++++++++++++++++++++--
2 files changed, 52 insertions(+), 2 deletions(-)
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 1bec2f7..165b6a2 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -111,6 +111,11 @@ asmlinkage int printk_emit(int facility, int level,
asmlinkage __printf(1, 2) __cold
int printk(const char *fmt, ...);
+bool printk_set_buffering(bool enable);
+bool printk_get_buffering(void);
+void printk_flush(void); /* forcibly emit any internal buffers */
+
+
/*
* Special printk facility for scheduler use only, _DO_NOT_USE_ !
*/
@@ -143,6 +148,17 @@ int printk(const char *s, ...)
{
return 0;
}
+static bool printk_set_buffering(bool enable)
+{
+ return false;
+}
+bool printk_get_buffering(void)
+{
+ return false;
+}
+static inline void printk_flush(void)
+{
+}
static inline __printf(1, 2) __cold
int printk_sched(const char *s, ...)
{
@@ -191,6 +207,8 @@ extern void dump_stack(void) __cold;
#define pr_cont(fmt, ...) \
printk(KERN_CONT fmt, ##__VA_ARGS__)
+#define pr_flush printk_flush
+
/* pr_devel() should produce zero code unless DEBUG is defined */
#ifdef DEBUG
#define pr_devel(fmt, ...) \
diff --git a/kernel/printk.c b/kernel/printk.c
index a2276b9..0e35931 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1144,6 +1144,23 @@ module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
"print all kernel messages to the console.");
+atomic_t printk_buffering = ATOMIC_INIT(1);
+
+bool printk_set_buffering(bool enable)
+{
+ if (enable)
+ return atomic_inc_and_test(&printk_buffering);
+
+ return atomic_dec_and_test(&printk_buffering);
+}
+EXPORT_SYMBOL(printk_set_buffering);
+
+bool printk_get_buffering(void)
+{
+ return atomic_read(&printk_buffering);
+}
+EXPORT_SYMBOL(printk_get_buffering);
+
/*
* Call the console drivers, asking them to write out
* log_buf[start] to log_buf[end - 1].
@@ -1288,6 +1305,7 @@ asmlinkage int vprintk_emit(int facility, int level,
int this_cpu;
bool newline = false;
bool prefix = false;
+ bool buffered = atomic_read(&printk_buffering);
int printed_len = 0;
boot_delay_msec();
@@ -1355,8 +1373,16 @@ asmlinkage int vprintk_emit(int facility, int level,
}
}
- if (level == -1)
+ switch (level) {
+ case -1:
level = default_message_loglevel;
+ break;
+ case -2:
+ prefix = true;
+ level = default_message_loglevel;
+ buffered = false;
+ break;
+ }
if (dict) {
prefix = true;
@@ -1364,7 +1390,7 @@ asmlinkage int vprintk_emit(int facility, int level,
}
if (!newline) {
- if (cont_len && (prefix || cont_task != current)) {
+ if (cont_len && (prefix || cont_task != current || !buffered)) {
/*
* Flush earlier buffer, which is either from a
* different thread, or when we got a new prefix.
@@ -1454,6 +1480,12 @@ asmlinkage int printk_emit(int facility, int level,
}
EXPORT_SYMBOL(printk_emit);
+void printk_flush(void)
+{
+ printk_emit(0, -2, NULL, 0, "printk_flush\n");
+}
+EXPORT_SYMBOL(printk_flush);
+
/**
* printk - print a kernel message
* @fmt: format string
--
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