From ab2e036fc81c938751c12a8d08a86705ee239f63 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Wed, 21 Jun 2023 22:06:23 +0200 Subject: [PATCH] 5.4-stable patches added patches: tick-common-align-tick-period-during-sched_timer-setup.patch --- queue-5.4/series | 1 + ...tick-period-during-sched_timer-setup.patch | 95 +++++++++++++++++++ 2 files changed, 96 insertions(+) create mode 100644 queue-5.4/tick-common-align-tick-period-during-sched_timer-setup.patch diff --git a/queue-5.4/series b/queue-5.4/series index 8a3d0a78e2c..5be7fd2160c 100644 --- a/queue-5.4/series +++ b/queue-5.4/series @@ -4,3 +4,4 @@ list-add-list_del_init_careful-to-go-with-list_empty.patch epoll-ep_autoremove_wake_function-should-use-list_de.patch tracing-add-tracing_reset_all_online_cpus_unlocked-function.patch x86-purgatory-remove-pgo-flags.patch +tick-common-align-tick-period-during-sched_timer-setup.patch diff --git a/queue-5.4/tick-common-align-tick-period-during-sched_timer-setup.patch b/queue-5.4/tick-common-align-tick-period-during-sched_timer-setup.patch new file mode 100644 index 00000000000..6480d977502 --- /dev/null +++ b/queue-5.4/tick-common-align-tick-period-during-sched_timer-setup.patch @@ -0,0 +1,95 @@ +From 13bb06f8dd42071cb9a49f6e21099eea05d4b856 Mon Sep 17 00:00:00 2001 +From: Thomas Gleixner +Date: Thu, 15 Jun 2023 11:18:30 +0200 +Subject: tick/common: Align tick period during sched_timer setup + +From: Thomas Gleixner + +commit 13bb06f8dd42071cb9a49f6e21099eea05d4b856 upstream. + +The tick period is aligned very early while the first clock_event_device is +registered. At that point the system runs in periodic mode and switches +later to one-shot mode if possible. + +The next wake-up event is programmed based on the aligned value +(tick_next_period) but the delta value, that is used to program the +clock_event_device, is computed based on ktime_get(). + +With the subtracted offset, the device fires earlier than the exact time +frame. With a large enough offset the system programs the timer for the +next wake-up and the remaining time left is too small to make any boot +progress. The system hangs. + +Move the alignment later to the setup of tick_sched timer. At this point +the system switches to oneshot mode and a high resolution clocksource is +available. At this point it is safe to align tick_next_period because +ktime_get() will now return accurate (not jiffies based) time. + +[bigeasy: Patch description + testing]. + +Fixes: e9523a0d81899 ("tick/common: Align tick period with the HZ tick.") +Reported-by: Mathias Krause +Reported-by: "Bhatnagar, Rishabh" +Suggested-by: Mathias Krause +Signed-off-by: Thomas Gleixner +Signed-off-by: Sebastian Andrzej Siewior +Signed-off-by: Thomas Gleixner +Tested-by: Richard W.M. Jones +Tested-by: Mathias Krause +Acked-by: SeongJae Park +Cc: stable@vger.kernel.org +Link: https://lore.kernel.org/5a56290d-806e-b9a5-f37c-f21958b5a8c0@grsecurity.net +Link: https://lore.kernel.org/12c6f9a3-d087-b824-0d05-0d18c9bc1bf3@amazon.com +Link: https://lore.kernel.org/r/20230615091830.RxMV2xf_@linutronix.de +Signed-off-by: Greg Kroah-Hartman +--- + kernel/time/tick-common.c | 13 +------------ + kernel/time/tick-sched.c | 13 ++++++++++++- + 2 files changed, 13 insertions(+), 13 deletions(-) + +--- a/kernel/time/tick-common.c ++++ b/kernel/time/tick-common.c +@@ -216,19 +216,8 @@ static void tick_setup_device(struct tic + * this cpu: + */ + if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { +- ktime_t next_p; +- u32 rem; +- + tick_do_timer_cpu = cpu; +- +- next_p = ktime_get(); +- div_u64_rem(next_p, TICK_NSEC, &rem); +- if (rem) { +- next_p -= rem; +- next_p += TICK_NSEC; +- } +- +- tick_next_period = next_p; ++ tick_next_period = ktime_get(); + #ifdef CONFIG_NO_HZ_FULL + /* + * The boot CPU may be nohz_full, in which case set +--- a/kernel/time/tick-sched.c ++++ b/kernel/time/tick-sched.c +@@ -129,8 +129,19 @@ static ktime_t tick_init_jiffy_update(vo + raw_spin_lock(&jiffies_lock); + write_seqcount_begin(&jiffies_seq); + /* Did we start the jiffies update yet ? */ +- if (last_jiffies_update == 0) ++ if (last_jiffies_update == 0) { ++ u32 rem; ++ ++ /* ++ * Ensure that the tick is aligned to a multiple of ++ * TICK_NSEC. ++ */ ++ div_u64_rem(tick_next_period, TICK_NSEC, &rem); ++ if (rem) ++ tick_next_period += TICK_NSEC - rem; ++ + last_jiffies_update = tick_next_period; ++ } + period = last_jiffies_update; + write_seqcount_end(&jiffies_seq); + raw_spin_unlock(&jiffies_lock); -- 2.47.3