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authorFrederic Weisbecker <fweisbec@gmail.com>2013-02-05 00:48:46 +0100
committerFrederic Weisbecker <fweisbec@gmail.com>2013-02-05 00:48:46 +0100
commit077931446b85e7858bf9dc0927cd116669b965d2 (patch)
tree02fbdf4a42b30b841a61aca399bd0ac6a5c308e6
parentf7c819c020db9796ae3a662b82a310617f92b15b (diff)
parent74876a98a87a115254b3a66a14b27320b7f0acaa (diff)
downloadvexpress-lsk-077931446b85e7858bf9dc0927cd116669b965d2.tar.gz
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>
-rw-r--r--include/linux/irq_work.h20
-rw-r--r--include/linux/printk.h3
-rw-r--r--include/linux/tick.h17
-rw-r--r--init/Kconfig1
-rw-r--r--kernel/irq_work.c112
-rw-r--r--kernel/printk.c36
-rw-r--r--kernel/time/tick-sched.c7
-rw-r--r--kernel/timer.c1
8 files changed, 147 insertions, 50 deletions
diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h
index ce60c084635..f5dbce50466 100644
--- a/include/linux/irq_work.h
+++ b/include/linux/irq_work.h
@@ -3,6 +3,20 @@
#include <linux/llist.h>
+/*
+ * An entry can be in one of four states:
+ *
+ * free NULL, 0 -> {claimed} : free to be used
+ * claimed NULL, 3 -> {pending} : claimed to be enqueued
+ * pending next, 3 -> {busy} : queued, pending callback
+ * busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
+ */
+
+#define IRQ_WORK_PENDING 1UL
+#define IRQ_WORK_BUSY 2UL
+#define IRQ_WORK_FLAGS 3UL
+#define IRQ_WORK_LAZY 4UL /* Doesn't want IPI, wait for tick */
+
struct irq_work {
unsigned long flags;
struct llist_node llnode;
@@ -20,4 +34,10 @@ void irq_work_queue(struct irq_work *work);
void irq_work_run(void);
void irq_work_sync(struct irq_work *work);
+#ifdef CONFIG_IRQ_WORK
+bool irq_work_needs_cpu(void);
+#else
+static bool irq_work_needs_cpu(void) { return false; }
+#endif
+
#endif /* _LINUX_IRQ_WORK_H */
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 9afc01e5a0a..86c4b629471 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -98,9 +98,6 @@ int no_printk(const char *fmt, ...)
extern asmlinkage __printf(1, 2)
void early_printk(const char *fmt, ...);
-extern int printk_needs_cpu(int cpu);
-extern void printk_tick(void);
-
#ifdef CONFIG_PRINTK
asmlinkage __printf(5, 0)
int vprintk_emit(int facility, int level,
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 1a6567b4849..553272e6af5 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -8,6 +8,8 @@
#include <linux/clockchips.h>
#include <linux/irqflags.h>
+#include <linux/percpu.h>
+#include <linux/hrtimer.h>
#ifdef CONFIG_GENERIC_CLOCKEVENTS
@@ -122,13 +124,26 @@ static inline int tick_oneshot_mode_active(void) { return 0; }
#endif /* !CONFIG_GENERIC_CLOCKEVENTS */
# ifdef CONFIG_NO_HZ
+DECLARE_PER_CPU(struct tick_sched, tick_cpu_sched);
+
+static inline int tick_nohz_tick_stopped(void)
+{
+ return __this_cpu_read(tick_cpu_sched.tick_stopped);
+}
+
extern void tick_nohz_idle_enter(void);
extern void tick_nohz_idle_exit(void);
extern void tick_nohz_irq_exit(void);
extern ktime_t tick_nohz_get_sleep_length(void);
extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
-# else
+
+# else /* !CONFIG_NO_HZ */
+static inline int tick_nohz_tick_stopped(void)
+{
+ return 0;
+}
+
static inline void tick_nohz_idle_enter(void) { }
static inline void tick_nohz_idle_exit(void) { }
diff --git a/init/Kconfig b/init/Kconfig
index e3227d7ba35..a98e1acc122 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1259,6 +1259,7 @@ config HOTPLUG
config PRINTK
default y
bool "Enable support for printk" if EXPERT
+ select IRQ_WORK
help
This option enables normal printk support. Removing it
eliminates most of the message strings from the kernel image
diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index c9d7478e488..55fcce6065c 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -12,22 +12,15 @@
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/irqflags.h>
+#include <linux/sched.h>
+#include <linux/tick.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
#include <asm/processor.h>
-/*
- * An entry can be in one of four states:
- *
- * free NULL, 0 -> {claimed} : free to be used
- * claimed NULL, 3 -> {pending} : claimed to be enqueued
- * pending next, 3 -> {busy} : queued, pending callback
- * busy NULL, 2 -> {free, claimed} : callback in progress, can be claimed
- */
-
-#define IRQ_WORK_PENDING 1UL
-#define IRQ_WORK_BUSY 2UL
-#define IRQ_WORK_FLAGS 3UL
static DEFINE_PER_CPU(struct llist_head, irq_work_list);
+static DEFINE_PER_CPU(int, irq_work_raised);
/*
* Claim the entry so that no one else will poke at it.
@@ -70,8 +63,6 @@ void __weak arch_irq_work_raise(void)
*/
void irq_work_queue(struct irq_work *work)
{
- bool empty;
-
/* Only queue if not already pending */
if (!irq_work_claim(work))
return;
@@ -79,30 +70,55 @@ void irq_work_queue(struct irq_work *work)
/* Queue the entry and raise the IPI if needed. */
preempt_disable();
- empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
- /* The list was empty, raise self-interrupt to start processing. */
- if (empty)
- arch_irq_work_raise();
+ llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
+
+ /*
+ * If the work is not "lazy" or the tick is stopped, raise the irq
+ * work interrupt (if supported by the arch), otherwise, just wait
+ * for the next tick.
+ */
+ if (!(work->flags & IRQ_WORK_LAZY) || tick_nohz_tick_stopped()) {
+ if (!this_cpu_cmpxchg(irq_work_raised, 0, 1))
+ arch_irq_work_raise();
+ }
preempt_enable();
}
EXPORT_SYMBOL_GPL(irq_work_queue);
-/*
- * Run the irq_work entries on this cpu. Requires to be ran from hardirq
- * context with local IRQs disabled.
- */
-void irq_work_run(void)
+bool irq_work_needs_cpu(void)
+{
+ struct llist_head *this_list;
+
+ this_list = &__get_cpu_var(irq_work_list);
+ if (llist_empty(this_list))
+ return false;
+
+ /* All work should have been flushed before going offline */
+ WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
+
+ return true;
+}
+
+static void __irq_work_run(void)
{
+ unsigned long flags;
struct irq_work *work;
struct llist_head *this_list;
struct llist_node *llnode;
+
+ /*
+ * Reset the "raised" state right before we check the list because
+ * an NMI may enqueue after we find the list empty from the runner.
+ */
+ __this_cpu_write(irq_work_raised, 0);
+ barrier();
+
this_list = &__get_cpu_var(irq_work_list);
if (llist_empty(this_list))
return;
- BUG_ON(!in_irq());
BUG_ON(!irqs_disabled());
llnode = llist_del_all(this_list);
@@ -118,15 +134,27 @@ void irq_work_run(void)
* to claim that work don't rely on us to handle their data
* while we are in the middle of the func.
*/
- xchg(&work->flags, IRQ_WORK_BUSY);
+ flags = work->flags & ~IRQ_WORK_PENDING;
+ xchg(&work->flags, flags);
+
work->func(work);
/*
* Clear the BUSY bit and return to the free state if
* no-one else claimed it meanwhile.
*/
- (void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
+ (void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
}
}
+
+/*
+ * Run the irq_work entries on this cpu. Requires to be ran from hardirq
+ * context with local IRQs disabled.
+ */
+void irq_work_run(void)
+{
+ BUG_ON(!in_irq());
+ __irq_work_run();
+}
EXPORT_SYMBOL_GPL(irq_work_run);
/*
@@ -141,3 +169,35 @@ void irq_work_sync(struct irq_work *work)
cpu_relax();
}
EXPORT_SYMBOL_GPL(irq_work_sync);
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int irq_work_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ long cpu = (long)hcpu;
+
+ switch (action) {
+ case CPU_DYING:
+ /* Called from stop_machine */
+ if (WARN_ON_ONCE(cpu != smp_processor_id()))
+ break;
+ __irq_work_run();
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block cpu_notify;
+
+static __init int irq_work_init_cpu_notifier(void)
+{
+ cpu_notify.notifier_call = irq_work_cpu_notify;
+ cpu_notify.priority = 0;
+ register_cpu_notifier(&cpu_notify);
+ return 0;
+}
+device_initcall(irq_work_init_cpu_notifier);
+
+#endif /* CONFIG_HOTPLUG_CPU */
diff --git a/kernel/printk.c b/kernel/printk.c
index 357f714ddd4..0b31715f335 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;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d58e552d9fd..fb8e5e469d1 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -20,6 +20,7 @@
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/module.h>
+#include <linux/irq_work.h>
#include <asm/irq_regs.h>
@@ -28,7 +29,7 @@
/*
* Per cpu nohz control structure
*/
-static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
+DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
/*
* The time, when the last jiffy update happened. Protected by jiffies_lock.
@@ -331,8 +332,8 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
time_delta = timekeeping_max_deferment();
} while (read_seqretry(&jiffies_lock, seq));
- if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) ||
- arch_needs_cpu(cpu)) {
+ if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
+ arch_needs_cpu(cpu) || irq_work_needs_cpu()) {
next_jiffies = last_jiffies + 1;
delta_jiffies = 1;
} else {
diff --git a/kernel/timer.c b/kernel/timer.c
index 367d0085848..ff3b5165737 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1351,7 +1351,6 @@ void update_process_times(int user_tick)
account_process_tick(p, user_tick);
run_local_timers();
rcu_check_callbacks(cpu, user_tick);
- printk_tick();
#ifdef CONFIG_IRQ_WORK
if (in_irq())
irq_work_run();