user/sven/linux.git/kernel/time/timer.c, branch v5.16.19

timers: implement usleep_idle_range()

2021-12-11T01:10:55Z

Patch series "mm/damon: Fix fake /proc/loadavg reports", v3. This patchset fixes DAMON's fake load report issue. The first patch makes yet another variant of usleep_range() for this fix, and the second patch fixes the issue of DAMON by making it using the newly introduced function. This patch (of 2): Some kernel threads such as DAMON could need to repeatedly sleep in micro seconds level. Because usleep_range() sleeps in uninterruptible state, however, such threads would make /proc/loadavg reports fake load. To help such cases, this commit implements a variant of usleep_range() called usleep_idle_range(). It is same to usleep_range() but sets the state of the current task as TASK_IDLE while sleeping. Link: https://lkml.kernel.org/r/20211126145015.15862-1-sj@kernel.org Link: https://lkml.kernel.org/r/20211126145015.15862-2-sj@kernel.org Signed-off-by: SeongJae Park Suggested-by: Andrew Morton Reviewed-by: Thomas Gleixner Tested-by: Oleksandr Natalenko Cc: John Stultz Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

timers: Move clearing of base::timer_running under base:: Lock

2021-07-27T18:57:44Z

syzbot reported KCSAN data races vs. timer_base::timer_running being set to NULL without holding base::lock in expire_timers(). This looks innocent and most reads are clearly not problematic, but Frederic identified an issue which is: int data = 0; void timer_func(struct timer_list *t) { data = 1; } CPU 0 CPU 1 ------------------------------ -------------------------- base = lock_timer_base(timer, &flags); raw_spin_unlock(&base->lock); if (base->running_timer != timer) call_timer_fn(timer, fn, baseclk); ret = detach_if_pending(timer, base, true); base->running_timer = NULL; raw_spin_unlock_irqrestore(&base->lock, flags); raw_spin_lock(&base->lock); x = data; If the timer has previously executed on CPU 1 and then CPU 0 can observe base->running_timer == NULL and returns, assuming the timer has completed, but it's not guaranteed on all architectures. The comment for del_timer_sync() makes that guarantee. Moving the assignment under base->lock prevents this. For non-RT kernel it's performance wise completely irrelevant whether the store happens before or after taking the lock. For an RT kernel moving the store under the lock requires an extra unlock/lock pair in the case that there is a waiter for the timer, but that's not the end of the world. Reported-by: syzbot+aa7c2385d46c5eba0b89@syzkaller.appspotmail.com Reported-by: syzbot+abea4558531bae1ba9fe@syzkaller.appspotmail.com Fixes: 030dcdd197d7 ("timers: Prepare support for PREEMPT_RT") Signed-off-by: Thomas Gleixner Tested-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/87lfea7gw8.fsf@nanos.tec.linutronix.de Cc: stable@vger.kernel.org

timers: Fix get_next_timer_interrupt() with no timers pending

2021-07-14T23:23:54Z

31cd0e119d50 ("timers: Recalculate next timer interrupt only when necessary") subtly altered get_next_timer_interrupt()'s behaviour. The function no longer consistently returns KTIME_MAX with no timers pending. In order to decide if there are any timers pending we check whether the next expiry will happen NEXT_TIMER_MAX_DELTA jiffies from now. Unfortunately, the next expiry time and the timer base clock are no longer updated in unison. The former changes upon certain timer operations (enqueue, expire, detach), whereas the latter keeps track of jiffies as they move forward. Ultimately breaking the logic above. A simplified example: - Upon entering get_next_timer_interrupt() with: jiffies = 1 base->clk = 0; base->next_expiry = NEXT_TIMER_MAX_DELTA; 'base->next_expiry == base->clk + NEXT_TIMER_MAX_DELTA', the function returns KTIME_MAX. - 'base->clk' is updated to the jiffies value. - The next time we enter get_next_timer_interrupt(), taking into account no timer operations happened: base->clk = 1; base->next_expiry = NEXT_TIMER_MAX_DELTA; 'base->next_expiry != base->clk + NEXT_TIMER_MAX_DELTA', the function returns a valid expire time, which is incorrect. This ultimately might unnecessarily rearm sched's timer on nohz_full setups, and add latency to the system[1]. So, introduce 'base->timers_pending'[2], update it every time 'base->next_expiry' changes, and use it in get_next_timer_interrupt(). [1] See tick_nohz_stop_tick(). [2] A quick pahole check on x86_64 and arm64 shows it doesn't make 'struct timer_base' any bigger. Fixes: 31cd0e119d50 ("timers: Recalculate next timer interrupt only when necessary") Signed-off-by: Nicolas Saenz Julienne Signed-off-by: Frederic Weisbecker

Merge branch 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

2021-07-04T19:58:33Z

Pull RCU updates from Paul McKenney: - Bitmap parsing support for "all" as an alias for all bits - Documentation updates - Miscellaneous fixes, including some that overlap into mm and lockdep - kvfree_rcu() updates - mem_dump_obj() updates, with acks from one of the slab-allocator maintainers - RCU NOCB CPU updates, including limited deoffloading - SRCU updates - Tasks-RCU updates - Torture-test updates * 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (78 commits) tasks-rcu: Make show_rcu_tasks_gp_kthreads() be static inline rcu-tasks: Make ksoftirqd provide RCU Tasks quiescent states rcu: Add missing __releases() annotation rcu: Remove obsolete rcu_read_unlock() deadlock commentary rcu: Improve comments describing RCU read-side critical sections rcu: Create an unrcu_pointer() to remove __rcu from a pointer srcu: Early test SRCU polling start rcu: Fix various typos in comments rcu/nocb: Unify timers rcu/nocb: Prepare for fine-grained deferred wakeup rcu/nocb: Only cancel nocb timer if not polling rcu/nocb: Delete bypass_timer upon nocb_gp wakeup rcu/nocb: Cancel nocb_timer upon nocb_gp wakeup rcu/nocb: Allow de-offloading rdp leader rcu/nocb: Directly call __wake_nocb_gp() from bypass timer rcu: Don't penalize priority boosting when there is nothing to boost rcu: Point to documentation of ordering guarantees rcu: Make rcu_gp_cleanup() be noinline for tracing rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs rcu: Make show_rcu_gp_kthreads() dump rcu_node structures blocking GP ...

sched,timer: Use __set_current_state()

2021-06-18T09:43:08Z

There's an existing helper for setting TASK_RUNNING; must've gotten lost last time we did this cleanup. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Davidlohr Bueso Acked-by: Will Deacon Link: https://lore.kernel.org/r/20210611082838.409696194@infradead.org

timer: Revert "timer: Add timer_curr_running()"

2021-05-10T23:02:44Z

This reverts commit dcd42591ebb8a25895b551a5297ea9c24414ba54. The only user was RCU/nocb. Signed-off-by: Frederic Weisbecker Cc: Josh Triplett Cc: Lai Jiangshan Cc: Joel Fernandes Cc: Neeraj Upadhyay Cc: Boqun Feng Cc: Thomas Gleixner Signed-off-by: Paul E. McKenney

timekeeping, clocksource: Fix various typos in comments

2021-03-22T22:06:48Z

Fix ~56 single-word typos in timekeeping & clocksource code comments. Signed-off-by: Ingo Molnar Cc: Thomas Gleixner Cc: John Stultz Cc: Stephen Boyd Cc: Daniel Lezcano Cc: linux-kernel@vger.kernel.org

rcu/nocb: Code-style nits in callback-offloading toggling

2021-01-07T00:47:55Z

This commit addresses a few code-style nits in callback-offloading toggling, including one that predates this toggling. Cc: Frederic Weisbecker Signed-off-by: Paul E. McKenney

timer: Add timer_curr_running()

2021-01-07T00:24:59Z

This commit adds a timer_curr_running() function that verifies that the current code is running in the context of the specified timer's handler. Cc: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Lai Jiangshan Cc: Joel Fernandes Cc: Neeraj Upadhyay Cc: Thomas Gleixner Tested-by: Boqun Feng Signed-off-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney

Merge tag 'timers-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-12-15T02:21:14Z

Pull timers and timekeeping updates from Thomas Gleixner: "Core: - Robustness improvements for the NOHZ tick management - Fixes and consolidation of the NTP/RTC synchronization code - Small fixes and improvements in various places - A set of function documentation udpates and fixes Drivers: - Cleanups and improvements in various clocksoure/event drivers - Removal of the EZChip NPS clocksource driver as the platfrom support was removed from ARC - The usual set of new device tree binding and json conversions - The RTC driver which have been acked by the RTC maintainer: * fix a long standing bug in the MC146818 library code which can cause reading garbage during the RTC internal update. * changes related to the NTP/RTC consolidation work" * tag 'timers-core-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (46 commits) ntp: Fix prototype in the !CONFIG_GENERIC_CMOS_UPDATE case tick/sched: Make jiffies update quick check more robust ntp: Consolidate the RTC update implementation ntp: Make the RTC sync offset less obscure ntp, rtc: Move rtc_set_ntp_time() to ntp code ntp: Make the RTC synchronization more reliable rtc: core: Make the sync offset default more realistic rtc: cmos: Make rtc_cmos sync offset correct rtc: mc146818: Reduce spinlock section in mc146818_set_time() rtc: mc146818: Prevent reading garbage clocksource/drivers/sh_cmt: Fix potential deadlock when calling runtime PM clocksource/drivers/arm_arch_timer: Correct fault programming of CNTKCTL_EL1.EVNTI clocksource/drivers/arm_arch_timer: Use stable count reader in erratum sne clocksource/drivers/dw_apb_timer_of: Add error handling if no clock available clocksource/drivers/riscv: Make RISCV_TIMER depends on RISCV_SBI clocksource/drivers/ingenic: Fix section mismatch clocksource/drivers/cadence_ttc: Fix memory leak in ttc_setup_clockevent() dt-bindings: timer: renesas: tmu: Convert to json-schema dt-bindings: timer: renesas: tmu: Document r8a774e1 bindings clocksource/drivers/orion: Add missing clk_disable_unprepare() on error path ...