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printk: Provide a wake_up_klogd() off-case 

wake_up_klogd() is useless when CONFIG_PRINTK=n because neither printk()
nor printk_sched() are in use and there are actually no waiter on
log_wait waitqueue.  It should be a stub in this case for users like
bust_spinlocks().

Otherwise this results in this warning when CONFIG_PRINTK=n and
CONFIG_IRQ_WORK=n:

	kernel/built-in.o In function `wake_up_klogd':
	(.text.wake_up_klogd+0xb4): undefined reference to `irq_work_queue'

To fix this, provide an off-case for wake_up_klogd() when
CONFIG_PRINTK=n.

There is much more from console_unlock() and other console related code
in printk.c that should be moved under CONFIG_PRINTK.  But for now,
focus on a minimal fix as we passed the merged window already.

[akpm@linux-foundation.org: include printk.h in bust_spinlocks.c]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reported-by: James Hogan <james.hogan@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Frederic Weisbecker 2013-03-22 15:04:39 -07:00 committed by Linus Torvalds
parent fe8d52614b
commit dc72c32e1f
4 changed files with 46 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/kernel.h
View File

@ -390,7 +390,6 @@ extern struct pid *session_of_pgrp(struct pid *pgrp);
unsigned long int_sqrt(unsigned long);
extern void bust_spinlocks(int yes);
extern void wake_up_klogd(void);
extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */
extern int panic_timeout;
extern int panic_on_oops;

6
include/linux/printk.h
View File

@ -134,6 +134,8 @@ extern int printk_delay_msec;
extern int dmesg_restrict;
extern int kptr_restrict;
extern void wake_up_klogd(void);
void log_buf_kexec_setup(void);
void __init setup_log_buf(int early);
#else
@ -162,6 +164,10 @@ static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies,
return false;
}
static inline void wake_up_klogd(void)
{
}
static inline void log_buf_kexec_setup(void)
{
}

80
kernel/printk.c
View File

@ -63,8 +63,6 @@ void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
DECLARE_WAIT_QUEUE_HEAD(log_wait);
int console_printk[4] = {
DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
@ -224,6 +222,7 @@ struct log {
static DEFINE_RAW_SPINLOCK(logbuf_lock);
#ifdef CONFIG_PRINTK
DECLARE_WAIT_QUEUE_HEAD(log_wait);
/* the next printk record to read by syslog(READ) or /proc/kmsg */
static u64 syslog_seq;
static u32 syslog_idx;
@ -1957,45 +1956,6 @@ int is_console_locked(void)
return console_locked;
}
/*
* Delayed printk version, for scheduler-internal messages:
*/
#define PRINTK_BUF_SIZE 512
#define PRINTK_PENDING_WAKEUP 0x01
#define PRINTK_PENDING_SCHED 0x02
static DEFINE_PER_CPU(int, printk_pending);
static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
static void wake_up_klogd_work_func(struct irq_work *irq_work)
{
int pending = __this_cpu_xchg(printk_pending, 0);
if (pending & PRINTK_PENDING_SCHED) {
char *buf = __get_cpu_var(printk_sched_buf);
printk(KERN_WARNING "[sched_delayed] %s", buf);
}
if (pending & PRINTK_PENDING_WAKEUP)
wake_up_interruptible(&log_wait);
}
static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
.func = wake_up_klogd_work_func,
.flags = IRQ_WORK_LAZY,
};
void wake_up_klogd(void)
{
preempt_disable();
if (waitqueue_active(&log_wait)) {
this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
}
preempt_enable();
}
static void console_cont_flush(char *text, size_t size)
{
unsigned long flags;
@ -2458,6 +2418,44 @@ static int __init printk_late_init(void)
late_initcall(printk_late_init);
#if defined CONFIG_PRINTK
/*
* Delayed printk version, for scheduler-internal messages:
*/
#define PRINTK_BUF_SIZE 512
#define PRINTK_PENDING_WAKEUP 0x01
#define PRINTK_PENDING_SCHED 0x02
static DEFINE_PER_CPU(int, printk_pending);
static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
static void wake_up_klogd_work_func(struct irq_work *irq_work)
{
int pending = __this_cpu_xchg(printk_pending, 0);
if (pending & PRINTK_PENDING_SCHED) {
char *buf = __get_cpu_var(printk_sched_buf);
printk(KERN_WARNING "[sched_delayed] %s", buf);
}
if (pending & PRINTK_PENDING_WAKEUP)
wake_up_interruptible(&log_wait);
}
static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
.func = wake_up_klogd_work_func,
.flags = IRQ_WORK_LAZY,
};
void wake_up_klogd(void)
{
preempt_disable();
if (waitqueue_active(&log_wait)) {
this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
}
preempt_enable();
}
int printk_sched(const char *fmt, ...)
{

3
lib/bust_spinlocks.c
View File

@ -8,6 +8,7 @@
*/
#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/spinlock.h>
#include <linux/tty.h>
#include <linux/wait.h>
@ -28,5 +29,3 @@ void __attribute__((weak)) bust_spinlocks(int yes)
wake_up_klogd();
}
}