time: Remove CONFIG_TIMER_STATS

Currently CONFIG_TIMER_STATS exposes process information across namespaces:

kernel/time/timer_list.c print_timer():

        SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);

/proc/timer_list:

 #11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570

Given that the tracer can give the same information, this patch entirely
removes CONFIG_TIMER_STATS.

Change-Id: I5147c4c1b4319cdabbc6d635b0d63f701b24ac30
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: linux-doc@vger.kernel.org
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Xing Gao <xgao01@email.wm.edu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jessica Frazelle <me@jessfraz.com>
Cc: kernel-hardening@lists.openwall.com
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Michal Marek <mmarek@suse.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-api@vger.kernel.org
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: http://lkml.kernel.org/r/20170208192659.GA32582@beast
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
haggertk: Backported to 3.4
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>

Documentation/timers/00-INDEX

@@ -8,5 +8,3 @@ hpet_example.c
 	- sample hpet timer test program
 hrtimers.txt
 	- subsystem for high-resolution kernel timers
-timer_stats.txt
-	- timer usage statistics

android/configs/android-recommended.cfg

@@ -106,7 +106,6 @@ CONFIG_TABLET_USB_GTCO=y
 CONFIG_TABLET_USB_HANWANG=y
 CONFIG_TABLET_USB_KBTAB=y
 CONFIG_TABLET_USB_WACOM=y
-CONFIG_TIMER_STATS=y
 CONFIG_TMPFS=y
 CONFIG_TMPFS_POSIX_ACL=y
 CONFIG_UHID=y

include/linux/hrtimer.h

@@ -96,12 +96,6 @@ enum hrtimer_restart {
  * @function:	timer expiry callback function
  * @base:	pointer to the timer base (per cpu and per clock)
  * @state:	state information (See bit values above)
- * @start_site:	timer statistics field to store the site where the timer
- *		was started
- * @start_comm: timer statistics field to store the name of the process which
- *		started the timer
- * @start_pid: timer statistics field to store the pid of the task which
- *		started the timer
  *
  * The hrtimer structure must be initialized by hrtimer_init()
  */
@@ -111,11 +105,6 @@ struct hrtimer {
 	enum hrtimer_restart		(*function)(struct hrtimer *);
 	struct hrtimer_clock_base	*base;
 	unsigned long			state;
-#ifdef CONFIG_TIMER_STATS
-	int				start_pid;
-	void				*start_site;
-	char				start_comm[16];
-#endif
 };
 
 /**

include/linux/timer.h

@@ -23,11 +23,6 @@ struct timer_list {
 
 	int slack;
 
-#ifdef CONFIG_TIMER_STATS
-	int start_pid;
-	void *start_site;
-	char start_comm[16];
-#endif
 #ifdef CONFIG_LOCKDEP
 	struct lockdep_map lockdep_map;
 #endif
@@ -229,49 +224,6 @@ extern void set_timer_slack(struct timer_list *time, int slack_hz);
  */
 extern unsigned long get_next_timer_interrupt(unsigned long now);
 
-/*
- * Timer-statistics info:
- */
-#ifdef CONFIG_TIMER_STATS
-
-extern int timer_stats_active;
-
-#define TIMER_STATS_FLAG_DEFERRABLE	0x1
-
-extern void init_timer_stats(void);
-
-extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
-				     void *timerf, char *comm,
-				     unsigned int timer_flag);
-
-extern void __timer_stats_timer_set_start_info(struct timer_list *timer,
-					       void *addr);
-
-static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
-{
-	if (likely(!timer_stats_active))
-		return;
-	__timer_stats_timer_set_start_info(timer, __builtin_return_address(0));
-}
-
-static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
-{
-	timer->start_site = NULL;
-}
-#else
-static inline void init_timer_stats(void)
-{
-}
-
-static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
-{
-}
-
-static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
-{
-}
-#endif
-
 extern void add_timer(struct timer_list *timer);
 
 extern int try_to_del_timer_sync(struct timer_list *timer);

kernel/hrtimer.c

@@ -757,34 +757,6 @@ void hrtimers_resume(void)
 	timerfd_clock_was_set();
 }
 
-static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
-{
-#ifdef CONFIG_TIMER_STATS
-	if (timer->start_site)
-		return;
-	timer->start_site = __builtin_return_address(0);
-	memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
-	timer->start_pid = current->pid;
-#endif
-}
-
-static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
-{
-#ifdef CONFIG_TIMER_STATS
-	timer->start_site = NULL;
-#endif
-}
-
-static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
-{
-#ifdef CONFIG_TIMER_STATS
-	if (likely(!timer_stats_active))
-		return;
-	timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
-				 timer->function, timer->start_comm, 0);
-#endif
-}
-
 /*
  * Counterpart to lock_hrtimer_base above:
  */
@@ -918,7 +890,6 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
 		 * rare case and less expensive than a smp call.
 		 */
 		debug_deactivate(timer);
-		timer_stats_hrtimer_clear_start_info(timer);
 		reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
 		/*
 		 * We must preserve the CALLBACK state flag here,
@@ -964,8 +935,6 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 
 	hrtimer_set_expires_range_ns(timer, tim, delta_ns);
 
-	timer_stats_hrtimer_set_start_info(timer);
-
 	leftmost = enqueue_hrtimer(timer, new_base);
 
 	/*
@@ -1154,12 +1123,6 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 	base = hrtimer_clockid_to_base(clock_id);
 	timer->base = &cpu_base->clock_base[base];
 	timerqueue_init(&timer->node);
-
-#ifdef CONFIG_TIMER_STATS
-	timer->start_site = NULL;
-	timer->start_pid = -1;
-	memset(timer->start_comm, 0, TASK_COMM_LEN);
-#endif
 }
 
 /**
@@ -1207,7 +1170,6 @@ static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
 
 	debug_deactivate(timer);
 	__remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
-	timer_stats_account_hrtimer(timer);
 	fn = timer->function;
 
 	/*

kernel/time/Makefile

@@ -6,4 +6,3 @@ obj-$(CONFIG_GENERIC_CLOCKEVENTS)		+= tick-common.o
 obj-$(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST)	+= tick-broadcast.o
 obj-$(CONFIG_TICK_ONESHOT)			+= tick-oneshot.o
 obj-$(CONFIG_TICK_ONESHOT)			+= tick-sched.o
-obj-$(CONFIG_TIMER_STATS)			+= timer_stats.o

kernel/time/timer_list.c

@@ -50,21 +50,11 @@ static void
 print_timer(struct seq_file *m, struct hrtimer *taddr, struct hrtimer *timer,
 	    int idx, u64 now)
 {
-#ifdef CONFIG_TIMER_STATS
-	char tmp[TASK_COMM_LEN + 1];
-#endif
 	SEQ_printf(m, " #%d: ", idx);
 	print_name_offset(m, taddr);
 	SEQ_printf(m, ", ");
 	print_name_offset(m, timer->function);
 	SEQ_printf(m, ", S:%02lx", timer->state);
-#ifdef CONFIG_TIMER_STATS
-	SEQ_printf(m, ", ");
-	print_name_offset(m, timer->start_site);
-	memcpy(tmp, timer->start_comm, TASK_COMM_LEN);
-	tmp[TASK_COMM_LEN] = 0;
-	SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);
-#endif
 	SEQ_printf(m, "\n");
 	SEQ_printf(m, " # expires at %Lu-%Lu nsecs [in %Ld to %Ld nsecs]\n",
 		(unsigned long long)ktime_to_ns(hrtimer_get_softexpires(timer)),

kernel/timer.c

@@ -372,34 +372,6 @@ static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 	list_add_tail(&timer->entry, vec);
 }
 
-#ifdef CONFIG_TIMER_STATS
-void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
-{
-	if (timer->start_site)
-		return;
-
-	timer->start_site = addr;
-	memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
-	timer->start_pid = current->pid;
-}
-
-static void timer_stats_account_timer(struct timer_list *timer)
-{
-	unsigned int flag = 0;
-
-	if (likely(!timer->start_site))
-		return;
-	if (unlikely(tbase_get_deferrable(timer->base)))
-		flag |= TIMER_STATS_FLAG_DEFERRABLE;
-
-	timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
-				 timer->function, timer->start_comm, flag);
-}
-
-#else
-static void timer_stats_account_timer(struct timer_list *timer) {}
-#endif
-
 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
 
 static struct debug_obj_descr timer_debug_descr;
@@ -606,11 +578,6 @@ static void __init_timer(struct timer_list *timer,
 	timer->entry.next = NULL;
 	timer->base = __raw_get_cpu_var(tvec_bases);
 	timer->slack = -1;
-#ifdef CONFIG_TIMER_STATS
-	timer->start_site = NULL;
-	timer->start_pid = -1;
-	memset(timer->start_comm, 0, TASK_COMM_LEN);
-#endif
 	lockdep_init_map(&timer->lockdep_map, name, key, 0);
 }
 
@@ -708,7 +675,6 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
 	unsigned long flags;
 	int ret = 0 , cpu;
 
-	timer_stats_timer_set_start_info(timer);
 	BUG_ON(!timer->function);
 
 	base = lock_timer_base(timer, &flags);
@@ -910,7 +876,6 @@ void add_timer_on(struct timer_list *timer, int cpu)
 	struct tvec_base *base = per_cpu(tvec_bases, cpu);
 	unsigned long flags;
 
-	timer_stats_timer_set_start_info(timer);
 	BUG_ON(timer_pending(timer) || !timer->function);
 	spin_lock_irqsave(&base->lock, flags);
 	timer_set_base(timer, base);
@@ -951,7 +916,6 @@ int del_timer(struct timer_list *timer)
 
 	debug_assert_init(timer);
 
-	timer_stats_timer_clear_start_info(timer);
 	if (timer_pending(timer)) {
 		base = lock_timer_base(timer, &flags);
 		if (timer_pending(timer)) {
@@ -988,7 +952,6 @@ int try_to_del_timer_sync(struct timer_list *timer)
 	if (base->running_timer == timer)
 		goto out;
 
-	timer_stats_timer_clear_start_info(timer);
 	ret = 0;
 	if (timer_pending(timer)) {
 		detach_timer(timer, 1);
@@ -1168,8 +1131,6 @@ static inline void __run_timers(struct tvec_base *base)
 			fn = timer->function;
 			data = timer->data;
 
-			timer_stats_account_timer(timer);
-
 			base->running_timer = timer;
 			detach_timer(timer, 1);
 
@@ -1784,8 +1745,6 @@ void __init init_timers(void)
 	int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
 				(void *)(long)smp_processor_id());
 
-	init_timer_stats();
-
 	BUG_ON(err != NOTIFY_OK);
 	register_cpu_notifier(&timers_nb);
 	open_softirq(TIMER_SOFTIRQ, run_timer_softirq);

kernel/workqueue.c

@@ -1136,8 +1136,6 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 		BUG_ON(timer_pending(timer));
 		BUG_ON(!list_empty(&work->entry));
 
-		timer_stats_timer_set_start_info(&dwork->timer);
-
 		/*
 		 * This stores cwq for the moment, for the timer_fn.
 		 * Note that the work's gcwq is preserved to allow

lib/Kconfig.debug

@@ -303,20 +303,6 @@ config SCHEDSTATS
 	  application, you can say N to avoid the very slight overhead
 	  this adds.
 
-config TIMER_STATS
-	bool "Collect kernel timers statistics"
-	depends on DEBUG_KERNEL && PROC_FS
-	help
-	  If you say Y here, additional code will be inserted into the
-	  timer routines to collect statistics about kernel timers being
-	  reprogrammed. The statistics can be read from /proc/timer_stats.
-	  The statistics collection is started by writing 1 to /proc/timer_stats,
-	  writing 0 stops it. This feature is useful to collect information
-	  about timer usage patterns in kernel and userspace. This feature
-	  is lightweight if enabled in the kernel config but not activated
-	  (it defaults to deactivated on bootup and will only be activated
-	  if some application like powertop activates it explicitly).
-
 config DEBUG_OBJECTS
 	bool "Debug object operations"
 	depends on DEBUG_KERNEL