hrtimer: removing all ur callback modes

Impact: cleanup, move all hrtimer processing into hardirq context

This is an attempt at removing some of the hrtimer complexity by
reducing the number of callback modes to 1.

This means that all hrtimer callback functions will be ran from HARD-irq
context.

I went through all the 30 odd hrtimer callback functions in the kernel
and saw only one that I'm not quite sure of, which is the one in
net/can/bcm.c - hence I'm CC-ing the folks responsible for that code.

Furthermore, the hrtimer core now calls callbacks directly with IRQs
disabled in case you try to enqueue an expired timer. If this timer is a
periodic timer (which should use hrtimer_forward() to advance its time)
then it might be possible to end up in an inf. recursive loop due to the
fact that hrtimer_forward() doesn't round up to the next timer
granularity, and therefore keeps on calling the callback - obviously
this needs a fix.

Aside from that, this seems to compile and actually boot on my dual core
test box - although I'm sure there are some bugs in, me not hitting any
makes me certain :-)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 2 insertions, 3 deletions

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 8ff15e5d486b..f5f793d92415 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -131,7 +131,7 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
 {
         enum hrtimer_restart res = HRTIMER_NORESTART;
 
-        write_seqlock_irq(&xtime_lock);
+        write_seqlock(&xtime_lock);
 
         switch (time_state) {
         case TIME_OK:
@@ -164,7 +164,7 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
         }
         update_vsyscall(&xtime, clock);
 
-        write_sequnlock_irq(&xtime_lock);
+        write_sequnlock(&xtime_lock);
 
         return res;
 }
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 342fc9ccab46..502a81e2639b 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -681,7 +681,6 @@ void tick_setup_sched_timer(void)
          */
         hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
         ts->sched_timer.function = tick_sched_timer;
-        ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_PERCPU;
 
         /* Get the next period (per cpu) */
         hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());