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>

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 80d36874689b40da26a3107ba509a8ca10dc74da..79fdd80a42d4f001157bc70b9570aa5eda0b8f6c 100644 (file)
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -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;

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 1249a54d17e0ab471501919dbdc8d63e27658c35..822171fcb1c82bd110472975d63fd4c2ed5fe8f2 100644 (file)
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -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)
 {
 }

diff --git a/kernel/printk.c b/kernel/printk.c
index 0b31715f335a7a8ba1a846fe3b93fe71d97cd8d7..abbdd9e2ac82c423a3dc6c778632c37887241b41 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -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, ...)
 {

diff --git a/lib/bust_spinlocks.c b/lib/bust_spinlocks.c
index 9681d54b95d127878405d5ff0afec6fcc575fbae..f8e0e536739832bdd05df68647e373788c060fda 100644 (file)
--- a/lib/bust_spinlocks.c
+++ b/lib/bust_spinlocks.c
@@ -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();
        }
 }
-
-