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authorSteven Rostedt <rostedt@goodmis.org>2013-06-26 15:28:11 -0400
committerAnders Roxell <anders.roxell@linaro.org>2015-08-17 08:59:57 +0200
commit609372369902409bc12dd13e731c22bbc8451747 (patch)
tree2678fa948390155f516210037ed723a2909222fa
parent826ff3fff878d1a72059c6e17bfb5165dc9b432f (diff)
downloadlinux-linaro-stable-609372369902409bc12dd13e731c22bbc8451747.tar.gz
rt,ntp: Move call to schedule_delayed_work() to helper thread
The ntp code for notify_cmos_timer() is called from a hard interrupt context. schedule_delayed_work() under PREEMPT_RT_FULL calls spinlocks that have been converted to mutexes, thus calling schedule_delayed_work() from interrupt is not safe. Add a helper thread that does the call to schedule_delayed_work and wake up that thread instead of calling schedule_delayed_work() directly. This is only for CONFIG_PREEMPT_RT_FULL, otherwise the code still calls schedule_delayed_work() directly in irq context. Note: There's a few places in the kernel that do this. Perhaps the RT code should have a dedicated thread that does the checks. Just register a notifier on boot up for your check and wake up the thread when needed. This will be a todo. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--kernel/time/ntp.c43
1 files changed, 43 insertions, 0 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 7a681003001c..bd9c53985d32 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -10,6 +10,7 @@
#include <linux/workqueue.h>
#include <linux/hrtimer.h>
#include <linux/jiffies.h>
+#include <linux/kthread.h>
#include <linux/math64.h>
#include <linux/timex.h>
#include <linux/time.h>
@@ -529,10 +530,52 @@ static void sync_cmos_clock(struct work_struct *work)
&sync_cmos_work, timespec_to_jiffies(&next));
}
+#ifdef CONFIG_PREEMPT_RT_FULL
+/*
+ * RT can not call schedule_delayed_work from real interrupt context.
+ * Need to make a thread to do the real work.
+ */
+static struct task_struct *cmos_delay_thread;
+static bool do_cmos_delay;
+
+static int run_cmos_delay(void *ignore)
+{
+ while (!kthread_should_stop()) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (do_cmos_delay) {
+ do_cmos_delay = false;
+ queue_delayed_work(system_power_efficient_wq,
+ &sync_cmos_work, 0);
+ }
+ schedule();
+ }
+ __set_current_state(TASK_RUNNING);
+ return 0;
+}
+
+void ntp_notify_cmos_timer(void)
+{
+ do_cmos_delay = true;
+ /* Make visible before waking up process */
+ smp_wmb();
+ wake_up_process(cmos_delay_thread);
+}
+
+static __init int create_cmos_delay_thread(void)
+{
+ cmos_delay_thread = kthread_run(run_cmos_delay, NULL, "kcmosdelayd");
+ BUG_ON(!cmos_delay_thread);
+ return 0;
+}
+early_initcall(create_cmos_delay_thread);
+
+#else
+
void ntp_notify_cmos_timer(void)
{
queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0);
}
+#endif /* CONFIG_PREEMPT_RT_FULL */
#else
void ntp_notify_cmos_timer(void) { }