Commit dc72c32e authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Linus Torvalds
Browse files

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: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Reported-by: default avatarJames 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fe8d5261

include/linux/kernel.h

+0 −1
Original line number Diff line number Diff line
@@ -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;

include/linux/printk.h

+6 −0
Original line number Diff line number Diff line
@@ -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)

{

}

kernel/printk.c

+39 −41
Original line number Diff line number Diff line
@@ -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, ...)

{

lib/bust_spinlocks.c

+1 −2
Original line number Diff line number Diff line
@@ -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();

	}

}

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