Merge branch 'nohz/printk-v8' into irq/core

Conflicts:
	kernel/irq_work.c

Add support for printk in full dynticks CPU.

* Don't stop tick with irq works pending. This
fix is generally useful and concerns archs that
can't raise self IPIs.

* Flush irq works before CPU offlining.

* Introduce "lazy" irq works that can wait for the
next tick to be executed, unless it's stopped.

* Implement klogd wake up using irq work. This
removes the ad-hoc printk_tick()/printk_needs_cpu()
hooks and make it working even in dynticks mode.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 20 insertions, 16 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 357f714ddd49..0b31715f335a 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -42,6 +42,7 @@
 #include <linux/notifier.h>
 #include <linux/rculist.h>
 #include <linux/poll.h>
+#include <linux/irq_work.h>
 
 #include <asm/uaccess.h>
 
@@ -1967,30 +1968,32 @@ int is_console_locked(void)
 static DEFINE_PER_CPU(int, printk_pending);
 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
 
-void printk_tick(void)
+static void wake_up_klogd_work_func(struct irq_work *irq_work)
 {
-        if (__this_cpu_read(printk_pending)) {
-                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);
+        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);
         }
-}
 
-int printk_needs_cpu(int cpu)
-{
-        if (cpu_is_offline(cpu))
-                printk_tick();
-        return __this_cpu_read(printk_pending);
+        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)
 {
-        if (waitqueue_active(&log_wait))
+        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)
@@ -2471,6 +2474,7 @@ int printk_sched(const char *fmt, ...)
         va_end(args);
 
         __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
+        irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
         local_irq_restore(flags);
 
         return r;