[PATCH V2 1/2] tick: Rename tick_do_update_jiffies64() and allow external usage

[PATCH V2 1/2] tick: Rename tick_do_update_jiffies64() and allow external usage

[Huacai Chen]

Rename tick_do_update_jiffies64() to do_update_jiffies_64() and move it
to jiffies.c. This keeps the same naming style in jiffies.c and allow it
be used by external components. This patch is a preparation for the next
one which attempts to avoid necessary rcu stall warnings.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
V2: Fix build.

 include/linux/jiffies.h   |   2 +
 kernel/time/jiffies.c     | 113 ++++++++++++++++++++++++++++++++++++-
 kernel/time/tick-sched.c  | 115 ++------------------------------------
 kernel/time/timekeeping.h |   1 +
 4 files changed, 118 insertions(+), 113 deletions(-)

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 5e13f801c902..48866314c68b 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -88,6 +88,8 @@ static inline u64 get_jiffies_64(void)
 }
 #endif
 
+void do_update_jiffies_64(s64 now); /* typedef s64 ktime_t */
+
 /*
  *	These inlines deal with timer wrapping correctly. You are 
  *	strongly encouraged to use them
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index bc4db9e5ab70..507a1e7e619e 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -5,14 +5,14 @@
  * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
  */
 #include <linux/clocksource.h>
+#include <linux/init.h>
 #include <linux/jiffies.h>
 #include <linux/module.h>
-#include <linux/init.h>
+#include <linux/sched/loadavg.h>
 
 #include "timekeeping.h"
 #include "tick-internal.h"
 
-
 static u64 jiffies_read(struct clocksource *cs)
 {
 	return (u64) jiffies;
@@ -61,6 +61,115 @@ EXPORT_SYMBOL(get_jiffies_64);
 
 EXPORT_SYMBOL(jiffies);
 
+/*
+ * The time, when the last jiffy update happened. Write access must hold
+ * jiffies_lock and jiffies_seq. Because tick_nohz_next_event() needs to
+ * get a consistent view of jiffies and last_jiffies_update.
+ */
+ktime_t last_jiffies_update;
+
+/*
+ * Must be called with interrupts disabled !
+ */
+void do_update_jiffies_64(ktime_t now)
+{
+#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
+	unsigned long ticks = 1;
+	ktime_t delta, nextp;
+
+	/*
+	 * 64bit can do a quick check without holding jiffies lock and
+	 * without looking at the sequence count. The smp_load_acquire()
+	 * pairs with the update done later in this function.
+	 *
+	 * 32bit cannot do that because the store of tick_next_period
+	 * consists of two 32bit stores and the first store could move it
+	 * to a random point in the future.
+	 */
+	if (IS_ENABLED(CONFIG_64BIT)) {
+		if (ktime_before(now, smp_load_acquire(&tick_next_period)))
+			return;
+	} else {
+		unsigned int seq;
+
+		/*
+		 * Avoid contention on jiffies_lock and protect the quick
+		 * check with the sequence count.
+		 */
+		do {
+			seq = read_seqcount_begin(&jiffies_seq);
+			nextp = tick_next_period;
+		} while (read_seqcount_retry(&jiffies_seq, seq));
+
+		if (ktime_before(now, nextp))
+			return;
+	}
+
+	/* Quick check failed, i.e. update is required. */
+	raw_spin_lock(&jiffies_lock);
+	/*
+	 * Reevaluate with the lock held. Another CPU might have done the
+	 * update already.
+	 */
+	if (ktime_before(now, tick_next_period)) {
+		raw_spin_unlock(&jiffies_lock);
+		return;
+	}
+
+	write_seqcount_begin(&jiffies_seq);
+
+	delta = ktime_sub(now, tick_next_period);
+	if (unlikely(delta >= TICK_NSEC)) {
+		/* Slow path for long idle sleep times */
+		s64 incr = TICK_NSEC;
+
+		ticks += ktime_divns(delta, incr);
+
+		last_jiffies_update = ktime_add_ns(last_jiffies_update,
+						   incr * ticks);
+	} else {
+		last_jiffies_update = ktime_add_ns(last_jiffies_update,
+						   TICK_NSEC);
+	}
+
+	/* Advance jiffies to complete the jiffies_seq protected job */
+	jiffies_64 += ticks;
+
+	/*
+	 * Keep the tick_next_period variable up to date.
+	 */
+	nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC);
+
+	if (IS_ENABLED(CONFIG_64BIT)) {
+		/*
+		 * Pairs with smp_load_acquire() in the lockless quick
+		 * check above and ensures that the update to jiffies_64 is
+		 * not reordered vs. the store to tick_next_period, neither
+		 * by the compiler nor by the CPU.
+		 */
+		smp_store_release(&tick_next_period, nextp);
+	} else {
+		/*
+		 * A plain store is good enough on 32bit as the quick check
+		 * above is protected by the sequence count.
+		 */
+		tick_next_period = nextp;
+	}
+
+	/*
+	 * Release the sequence count. calc_global_load() below is not
+	 * protected by it, but jiffies_lock needs to be held to prevent
+	 * concurrent invocations.
+	 */
+	write_seqcount_end(&jiffies_seq);
+
+	calc_global_load();
+
+	raw_spin_unlock(&jiffies_lock);
+	update_wall_time();
+#endif
+}
+
 static int __init init_jiffies_clocksource(void)
 {
 	return __clocksource_register(&clocksource_jiffies);
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 4df14db4da49..c993c7dfe79d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -44,113 +44,6 @@ struct tick_sched *tick_get_tick_sched(int cpu)
 }
 
 #if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
-/*
- * The time, when the last jiffy update happened. Write access must hold
- * jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a
- * consistent view of jiffies and last_jiffies_update.
- */
-static ktime_t last_jiffies_update;
-
-/*
- * Must be called with interrupts disabled !
- */
-static void tick_do_update_jiffies64(ktime_t now)
-{
-	unsigned long ticks = 1;
-	ktime_t delta, nextp;
-
-	/*
-	 * 64bit can do a quick check without holding jiffies lock and
-	 * without looking at the sequence count. The smp_load_acquire()
-	 * pairs with the update done later in this function.
-	 *
-	 * 32bit cannot do that because the store of tick_next_period
-	 * consists of two 32bit stores and the first store could move it
-	 * to a random point in the future.
-	 */
-	if (IS_ENABLED(CONFIG_64BIT)) {
-		if (ktime_before(now, smp_load_acquire(&tick_next_period)))
-			return;
-	} else {
-		unsigned int seq;
-
-		/*
-		 * Avoid contention on jiffies_lock and protect the quick
-		 * check with the sequence count.
-		 */
-		do {
-			seq = read_seqcount_begin(&jiffies_seq);
-			nextp = tick_next_period;
-		} while (read_seqcount_retry(&jiffies_seq, seq));
-
-		if (ktime_before(now, nextp))
-			return;
-	}
-
-	/* Quick check failed, i.e. update is required. */
-	raw_spin_lock(&jiffies_lock);
-	/*
-	 * Reevaluate with the lock held. Another CPU might have done the
-	 * update already.
-	 */
-	if (ktime_before(now, tick_next_period)) {
-		raw_spin_unlock(&jiffies_lock);
-		return;
-	}
-
-	write_seqcount_begin(&jiffies_seq);
-
-	delta = ktime_sub(now, tick_next_period);
-	if (unlikely(delta >= TICK_NSEC)) {
-		/* Slow path for long idle sleep times */
-		s64 incr = TICK_NSEC;
-
-		ticks += ktime_divns(delta, incr);
-
-		last_jiffies_update = ktime_add_ns(last_jiffies_update,
-						   incr * ticks);
-	} else {
-		last_jiffies_update = ktime_add_ns(last_jiffies_update,
-						   TICK_NSEC);
-	}
-
-	/* Advance jiffies to complete the jiffies_seq protected job */
-	jiffies_64 += ticks;
-
-	/*
-	 * Keep the tick_next_period variable up to date.
-	 */
-	nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC);
-
-	if (IS_ENABLED(CONFIG_64BIT)) {
-		/*
-		 * Pairs with smp_load_acquire() in the lockless quick
-		 * check above and ensures that the update to jiffies_64 is
-		 * not reordered vs. the store to tick_next_period, neither
-		 * by the compiler nor by the CPU.
-		 */
-		smp_store_release(&tick_next_period, nextp);
-	} else {
-		/*
-		 * A plain store is good enough on 32bit as the quick check
-		 * above is protected by the sequence count.
-		 */
-		tick_next_period = nextp;
-	}
-
-	/*
-	 * Release the sequence count. calc_global_load() below is not
-	 * protected by it, but jiffies_lock needs to be held to prevent
-	 * concurrent invocations.
-	 */
-	write_seqcount_end(&jiffies_seq);
-
-	calc_global_load();
-
-	raw_spin_unlock(&jiffies_lock);
-	update_wall_time();
-}
-
 /*
  * Initialize and return retrieve the jiffies update.
  */
@@ -207,7 +100,7 @@ static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
 
 	/* Check, if the jiffies need an update */
 	if (tick_do_timer_cpu == cpu)
-		tick_do_update_jiffies64(now);
+		do_update_jiffies_64(now);
 
 	/*
 	 * If jiffies update stalled for too long (timekeeper in stop_machine()
@@ -218,7 +111,7 @@ static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
 		ts->last_tick_jiffies = READ_ONCE(jiffies);
 	} else {
 		if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) {
-			tick_do_update_jiffies64(now);
+			tick_do_update_jiffies_64(now);
 			ts->stalled_jiffies = 0;
 			ts->last_tick_jiffies = READ_ONCE(jiffies);
 		}
@@ -652,7 +545,7 @@ static void tick_nohz_update_jiffies(ktime_t now)
 	__this_cpu_write(tick_cpu_sched.idle_waketime, now);
 
 	local_irq_save(flags);
-	tick_do_update_jiffies64(now);
+	do_update_jiffies_64(now);
 	local_irq_restore(flags);
 
 	touch_softlockup_watchdog_sched();
@@ -975,7 +868,7 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts, int cpu)
 static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
 {
 	/* Update jiffies first */
-	tick_do_update_jiffies64(now);
+	do_update_jiffies_64(now);
 
 	/*
 	 * Clear the timer idle flag, so we avoid IPIs on remote queueing and
diff --git a/kernel/time/timekeeping.h b/kernel/time/timekeeping.h
index 543beba096c7..21670f6c7421 100644
--- a/kernel/time/timekeeping.h
+++ b/kernel/time/timekeeping.h
@@ -28,6 +28,7 @@ extern void update_wall_time(void);
 
 extern raw_spinlock_t jiffies_lock;
 extern seqcount_raw_spinlock_t jiffies_seq;
+extern ktime_t last_jiffies_update;
 
 #define CS_NAME_LEN	32
 
-- 
2.39.3

[PATCH V2 2/2] rcu: Update jiffies in rcu_cpu_stall_reset()

[Huacai Chen]

The KGDB initial breakpoint gets an rcu stall warning after commit
a80be428fbc1f1f3bc9ed924 ("rcu: Do not disable GP stall detection in
rcu_cpu_stall_reset()").

[   53.452051] rcu: INFO: rcu_preempt self-detected stall on CPU
[   53.487950] rcu:     3-...0: (1 ticks this GP) idle=0e2c/1/0x4000000000000000 softirq=375/375 fqs=8
[   53.528243] rcu:     (t=12297 jiffies g=-995 q=1 ncpus=4)
[   53.564840] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 6.5.0-rc2+ #4848
[   53.603005] Hardware name: Loongson Loongson-3A5000-HV-7A2000-1w-V0.1-CRB/Loongson-LS3A5000-7A2000-1w-CRB-V1.21, BIOS Loongson-UDK2018-V2.0.05099-beta8 08
[   53.682062] pc 9000000000332100 ra 90000000003320f4 tp 90000001000a0000 sp 90000001000a3710
[   53.724934] a0 9000000001d4b488 a1 0000000000000000 a2 0000000000000001 a3 0000000000000000
[   53.768179] a4 9000000001d526c8 a5 90000001000a38f0 a6 000000000000002c a7 0000000000000000
[   53.810751] t0 00000000000002b0 t1 0000000000000004 t2 900000000131c9c0 t3 fffffffffffffffa
[   53.853249] t4 0000000000000080 t5 90000001002ac190 t6 0000000000000004 t7 9000000001912d58
[   53.895684] t8 0000000000000000 u0 90000000013141a0 s9 0000000000000028 s0 9000000001d512f0
[   53.937633] s1 9000000001d51278 s2 90000001000a3798 s3 90000000019fc410 s4 9000000001d4b488
[   53.979486] s5 9000000001d512f0 s6 90000000013141a0 s7 0000000000000078 s8 9000000001d4b450
[   54.021175]    ra: 90000000003320f4 kgdb_cpu_enter+0x534/0x640
[   54.060150]   ERA: 9000000000332100 kgdb_cpu_enter+0x540/0x640
[   54.098347]  CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE)
[   54.136621]  PRMD: 0000000c (PPLV0 +PIE +PWE)
[   54.172192]  EUEN: 00000000 (-FPE -SXE -ASXE -BTE)
[   54.207838]  ECFG: 00071c1c (LIE=2-4,10-12 VS=7)
[   54.242503] ESTAT: 00000800 [INT] (IS=11 ECode=0 EsubCode=0)
[   54.277996]  PRID: 0014c011 (Loongson-64bit, Loongson-3A5000-HV)
[   54.313544] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 6.5.0-rc2+ #4848
[   54.430170] Stack : 0072617764726148 0000000000000000 9000000000223504 90000001000a0000
[   54.472308]         9000000100073a90 9000000100073a98 0000000000000000 9000000100073bd8
[   54.514413]         9000000100073bd0 9000000100073bd0 9000000100073a00 0000000000000001
[   54.556018]         0000000000000001 9000000100073a98 99828271f24e961a 90000001002810c0
[   54.596924]         0000000000000001 0000000000010003 0000000000000000 0000000000000001
[   54.637115]         ffff8000337cdb80 0000000000000001 0000000006360000 900000000131c9c0
[   54.677049]         0000000000000000 0000000000000000 90000000017b4c98 9000000001912000
[   54.716394]         9000000001912f68 9000000001913000 9000000001912f70 00000000000002b0
[   54.754880]         90000000014a8840 0000000000000000 900000000022351c 0000000000000000
[   54.792372]         00000000000002b0 000000000000000c 0000000000000000 0000000000071c1c
[   54.829302]         ...
[   54.859163] Call Trace:
[   54.859165] [<900000000022351c>] show_stack+0x5c/0x180
[   54.918298] [<90000000012f6100>] dump_stack_lvl+0x60/0x88
[   54.949251] [<90000000012dd5d8>] rcu_dump_cpu_stacks+0xf0/0x148
[   54.981116] [<90000000002d2fb8>] rcu_sched_clock_irq+0xb78/0xe60
[   55.012744] [<90000000002e47cc>] update_process_times+0x6c/0xc0
[   55.044169] [<90000000002f65d4>] tick_sched_timer+0x54/0x100
[   55.075488] [<90000000002e5174>] __hrtimer_run_queues+0x154/0x240
[   55.107347] [<90000000002e6288>] hrtimer_interrupt+0x108/0x2a0
[   55.139112] [<9000000000226418>] constant_timer_interrupt+0x38/0x60
[   55.170749] [<90000000002b3010>] __handle_irq_event_percpu+0x50/0x160
[   55.203141] [<90000000002b3138>] handle_irq_event_percpu+0x18/0x80
[   55.235064] [<90000000002b9d54>] handle_percpu_irq+0x54/0xa0
[   55.266241] [<90000000002b2168>] generic_handle_domain_irq+0x28/0x40
[   55.298466] [<9000000000aba95c>] handle_cpu_irq+0x5c/0xa0
[   55.329749] [<90000000012f7270>] handle_loongarch_irq+0x30/0x60
[   55.361476] [<90000000012f733c>] do_vint+0x9c/0x100
[   55.391737] [<9000000000332100>] kgdb_cpu_enter+0x540/0x640
[   55.422440] [<9000000000332b64>] kgdb_handle_exception+0x104/0x180
[   55.452911] [<9000000000232478>] kgdb_loongarch_notify+0x38/0xa0
[   55.481964] [<900000000026b4d4>] notify_die+0x94/0x100
[   55.509184] [<90000000012f685c>] do_bp+0x21c/0x340
[   55.562475] [<90000000003315b8>] kgdb_compiled_break+0x0/0x28
[   55.590319] [<9000000000332e80>] kgdb_register_io_module+0x160/0x1c0
[   55.618901] [<9000000000c0f514>] configure_kgdboc+0x154/0x1c0
[   55.647034] [<9000000000c0f5e0>] kgdboc_probe+0x60/0x80
[   55.674647] [<9000000000c96da8>] platform_probe+0x68/0x100
[   55.702613] [<9000000000c938e0>] really_probe+0xc0/0x340
[   55.730528] [<9000000000c93be4>] __driver_probe_device+0x84/0x140
[   55.759615] [<9000000000c93cdc>] driver_probe_device+0x3c/0x120
[   55.787990] [<9000000000c93e8c>] __device_attach_driver+0xcc/0x160
[   55.817145] [<9000000000c91290>] bus_for_each_drv+0x90/0x100
[   55.845654] [<9000000000c94328>] __device_attach+0xa8/0x1a0
[   55.874145] [<9000000000c925f0>] bus_probe_device+0xb0/0xe0
[   55.902572] [<9000000000c8ec7c>] device_add+0x65c/0x860
[   55.930635] [<9000000000c96704>] platform_device_add+0x124/0x2c0
[   55.959669] [<9000000001452b38>] init_kgdboc+0x58/0xa0
[   55.987677] [<900000000022015c>] do_one_initcall+0x7c/0x1e0
[   56.016134] [<9000000001420f1c>] kernel_init_freeable+0x22c/0x2a0
[   56.045128] [<90000000012f923c>] kernel_init+0x20/0x124

Currently rcu_cpu_stall_reset() set rcu_state.jiffies_stall to one check
period later, i.e. jiffies + rcu_jiffies_till_stall_check(). But jiffies
is only updated in the timer interrupt, so when kgdb_cpu_enter() begins
to run there may already be nearly one rcu check period after jiffies.
Since all interrupts are disabled during kgdb_cpu_enter(), jiffies will
not be updated. When kgdb_cpu_enter() returns, rcu_state.jiffies_stall
maybe already gets timeout.

We can set rcu_state.jiffies_stall to two rcu check periods later, e.g.
jiffies + (rcu_jiffies_till_stall_check() * 2) in rcu_cpu_stall_reset()
to avoid this problem. But this isn't a complete solution because kgdb
may take a very long time in irq disabled context.

Instead, update jiffies at the beginning of rcu_cpu_stall_reset() can
solve all kinds of problems.

Cc: stable@vger.kernel.org
Fixes: a80be428fbc1f1f3bc9ed924 ("rcu: Do not disable GP stall detection in rcu_cpu_stall_reset()")
Reported-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 kernel/rcu/tree_stall.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index b10b8349bb2a..1c7b540985bf 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -153,6 +153,7 @@ static void panic_on_rcu_stall(void)
  */
 void rcu_cpu_stall_reset(void)
 {
+	do_update_jiffies_64(ktime_get());
 	WRITE_ONCE(rcu_state.jiffies_stall,
 		   jiffies + rcu_jiffies_till_stall_check());
 }
-- 
2.39.3

Re: [PATCH V2 1/2] tick: Rename tick_do_update_jiffies64() and allow external usage

[kernel test robot]

Hi Huacai,

kernel test robot noticed the following build errors:

[auto build test ERROR on paulmck-rcu/dev]
[also build test ERROR on linus/master]
[cannot apply to tip/timers/nohz]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Huacai-Chen/rcu-Update-jiffies-in-rcu_cpu_stall_reset/20230810-142629
base:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
patch link:    https://lore.kernel.org/r/20230810062527.3700080-1-chenhuacai%40loongson.cn
patch subject: [PATCH V2 1/2] tick: Rename tick_do_update_jiffies64() and allow external usage
config: powerpc-randconfig-r013-20230809 (https://download.01.org/0day-ci/archive/20230810/202308101853.wOMMd0Tf-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project.git 4a5ac14ee968ff0ad5d2cc1ffa0299048db4c88a)
reproduce: (https://download.01.org/0day-ci/archive/20230810/202308101853.wOMMd0Tf-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308101853.wOMMd0Tf-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/linux/io.h:13:
   In file included from arch/powerpc/include/asm/io.h:677:
   arch/powerpc/include/asm/io-defs.h:45:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
      45 | DEF_PCI_AC_NORET(insw, (unsigned long p, void *b, unsigned long c),
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      46 |                  (p, b, c), pio, p)
         |                  ~~~~~~~~~~~~~~~~~~
   arch/powerpc/include/asm/io.h:674:3: note: expanded from macro 'DEF_PCI_AC_NORET'
     674 |                 __do_##name al;                                 \
         |                 ^~~~~~~~~~~~~~
   <scratch space>:49:1: note: expanded from here
      49 | __do_insw
         | ^
   arch/powerpc/include/asm/io.h:615:56: note: expanded from macro '__do_insw'
     615 | #define __do_insw(p, b, n)      readsw((PCI_IO_ADDR)_IO_BASE+(p), (b), (n))
         |                                        ~~~~~~~~~~~~~~~~~~~~~^
   In file included from kernel/time/tick-sched.c:14:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/powerpc/include/asm/hardirq.h:6:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/powerpc/include/asm/io.h:677:
   arch/powerpc/include/asm/io-defs.h:47:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
      47 | DEF_PCI_AC_NORET(insl, (unsigned long p, void *b, unsigned long c),
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      48 |                  (p, b, c), pio, p)
         |                  ~~~~~~~~~~~~~~~~~~
   arch/powerpc/include/asm/io.h:674:3: note: expanded from macro 'DEF_PCI_AC_NORET'
     674 |                 __do_##name al;                                 \
         |                 ^~~~~~~~~~~~~~
   <scratch space>:51:1: note: expanded from here
      51 | __do_insl
         | ^
   arch/powerpc/include/asm/io.h:616:56: note: expanded from macro '__do_insl'
     616 | #define __do_insl(p, b, n)      readsl((PCI_IO_ADDR)_IO_BASE+(p), (b), (n))
         |                                        ~~~~~~~~~~~~~~~~~~~~~^
   In file included from kernel/time/tick-sched.c:14:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/powerpc/include/asm/hardirq.h:6:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/powerpc/include/asm/io.h:677:
   arch/powerpc/include/asm/io-defs.h:49:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
      49 | DEF_PCI_AC_NORET(outsb, (unsigned long p, const void *b, unsigned long c),
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      50 |                  (p, b, c), pio, p)
         |                  ~~~~~~~~~~~~~~~~~~
   arch/powerpc/include/asm/io.h:674:3: note: expanded from macro 'DEF_PCI_AC_NORET'
     674 |                 __do_##name al;                                 \
         |                 ^~~~~~~~~~~~~~
   <scratch space>:53:1: note: expanded from here
      53 | __do_outsb
         | ^
   arch/powerpc/include/asm/io.h:617:58: note: expanded from macro '__do_outsb'
     617 | #define __do_outsb(p, b, n)     writesb((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
         |                                         ~~~~~~~~~~~~~~~~~~~~~^
   In file included from kernel/time/tick-sched.c:14:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/powerpc/include/asm/hardirq.h:6:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/powerpc/include/asm/io.h:677:
   arch/powerpc/include/asm/io-defs.h:51:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
      51 | DEF_PCI_AC_NORET(outsw, (unsigned long p, const void *b, unsigned long c),
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      52 |                  (p, b, c), pio, p)
         |                  ~~~~~~~~~~~~~~~~~~
   arch/powerpc/include/asm/io.h:674:3: note: expanded from macro 'DEF_PCI_AC_NORET'
     674 |                 __do_##name al;                                 \
         |                 ^~~~~~~~~~~~~~
   <scratch space>:55:1: note: expanded from here
      55 | __do_outsw
         | ^
   arch/powerpc/include/asm/io.h:618:58: note: expanded from macro '__do_outsw'
     618 | #define __do_outsw(p, b, n)     writesw((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
         |                                         ~~~~~~~~~~~~~~~~~~~~~^
   In file included from kernel/time/tick-sched.c:14:
   In file included from include/linux/interrupt.h:11:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/powerpc/include/asm/hardirq.h:6:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/powerpc/include/asm/io.h:677:
   arch/powerpc/include/asm/io-defs.h:53:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
      53 | DEF_PCI_AC_NORET(outsl, (unsigned long p, const void *b, unsigned long c),
         | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      54 |                  (p, b, c), pio, p)
         |                  ~~~~~~~~~~~~~~~~~~
   arch/powerpc/include/asm/io.h:674:3: note: expanded from macro 'DEF_PCI_AC_NORET'
     674 |                 __do_##name al;                                 \
         |                 ^~~~~~~~~~~~~~
   <scratch space>:57:1: note: expanded from here
      57 | __do_outsl
         | ^
   arch/powerpc/include/asm/io.h:619:58: note: expanded from macro '__do_outsl'
     619 | #define __do_outsl(p, b, n)     writesl((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
         |                                         ~~~~~~~~~~~~~~~~~~~~~^
>> kernel/time/tick-sched.c:114:4: error: call to undeclared function 'tick_do_update_jiffies_64'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     114 |                         tick_do_update_jiffies_64(now);
         |                         ^
   kernel/time/tick-sched.c:114:4: note: did you mean 'do_update_jiffies_64'?
   include/linux/jiffies.h:91:6: note: 'do_update_jiffies_64' declared here
      91 | void do_update_jiffies_64(s64 now); /* typedef s64 ktime_t */
         |      ^
   6 warnings and 1 error generated.


vim +/tick_do_update_jiffies_64 +114 kernel/time/tick-sched.c

   100	
   101		/* Check, if the jiffies need an update */
   102		if (tick_do_timer_cpu == cpu)
   103			do_update_jiffies_64(now);
   104	
   105		/*
   106		 * If jiffies update stalled for too long (timekeeper in stop_machine()
   107		 * or VMEXIT'ed for several msecs), force an update.
   108		 */
   109		if (ts->last_tick_jiffies != jiffies) {
   110			ts->stalled_jiffies = 0;
   111			ts->last_tick_jiffies = READ_ONCE(jiffies);
   112		} else {
   113			if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) {
 > 114				tick_do_update_jiffies_64(now);
   115				ts->stalled_jiffies = 0;
   116				ts->last_tick_jiffies = READ_ONCE(jiffies);
   117			}
   118		}
   119	
   120		if (ts->inidle)
   121			ts->got_idle_tick = 1;
   122	}
   123	

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