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author | Steven Rostedt <rostedt@goodmis.org> | 2013-06-26 19:28:11 (GMT) |
---|---|---|
committer | Scott Wood <scottwood@freescale.com> | 2014-04-10 00:20:17 (GMT) |
commit | 66fc1a4436cb3a79d597c14dcb8ce25bdbd6214e (patch) | |
tree | 21ea8440e6d1d94f81ffc5bfdef7a063318c005b | |
parent | 1273b9566225d091a44f46630266f08808b62f87 (diff) | |
download | linux-fsl-qoriq-66fc1a4436cb3a79d597c14dcb8ce25bdbd6214e.tar.xz |
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.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index af8d1d4..d6132cd 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> @@ -517,10 +518,49 @@ static void sync_cmos_clock(struct work_struct *work) schedule_delayed_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; + schedule_delayed_work(&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) { schedule_delayed_work(&sync_cmos_work, 0); } +#endif /* CONFIG_PREEMPT_RT_FULL */ #else void ntp_notify_cmos_timer(void) { } |