Revert "hrtimer: Report offline hrtimer enqueue"

This reverts commit 15524057a390fee95c2a57b3948efa66e5b58e7c which is
commit dad6a09f3148257ac1773cd90934d721d68ab595 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I3946038162ecfa5fafc8721ac4aaa8545ed540e2
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

include/linux/hrtimer.h

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 9575162..f5d4392 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -200,7 +200,6 @@ enum  hrtimer_base_type {
  * @max_hang_time:	Maximum time spent in hrtimer_interrupt
  * @softirq_expiry_lock: Lock which is taken while softirq based hrtimer are
  *			 expired
- * @online:		CPU is online from an hrtimers point of view
  * @timer_waiters:	A hrtimer_cancel() invocation waits for the timer
  *			callback to finish.
  * @expires_next:	absolute time of the next event, is required for remote
@@ -223,8 +222,7 @@ struct hrtimer_cpu_base {
 	unsigned int			hres_active		: 1,
 					in_hrtirq		: 1,
 					hang_detected		: 1,
-					softirq_activated       : 1,
-					online			: 1;
+					softirq_activated       : 1;
 #ifdef CONFIG_HIGH_RES_TIMERS
 	unsigned int			nr_events;
 	unsigned short			nr_retries;

kernel/time/hrtimer.c

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index b699930..debf34b2 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1082,7 +1082,6 @@ static int enqueue_hrtimer(struct hrtimer *timer,
 			   enum hrtimer_mode mode)
 {
 	debug_activate(timer, mode);
-	WARN_ON_ONCE(!base->cpu_base->online);
 
 	base->cpu_base->active_bases |= 1 << base->index;
 
@@ -2181,7 +2180,6 @@ int hrtimers_prepare_cpu(unsigned int cpu)
 	cpu_base->softirq_next_timer = NULL;
 	cpu_base->expires_next = KTIME_MAX;
 	cpu_base->softirq_expires_next = KTIME_MAX;
-	cpu_base->online = 1;
 	hrtimer_cpu_base_init_expiry_lock(cpu_base);
 	return 0;
 }