Messages in this thread | | | Subject | Re: [PATCH 0/4] sched/idle: Fix missing need_resched() checks after rcu_idle_enter() | From | "Rafael J. Wysocki" <> | Date | Tue, 22 Dec 2020 17:19:51 +0100 |
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On 12/22/2020 2:37 AM, Frederic Weisbecker wrote: > With Paul, we've been thinking that the idle loop wasn't twisted enough > yet to deserve 2020. > > rcutorture, after some recent parameter changes, has been complaining > about a hung task. > > It appears that rcu_idle_enter() may wake up a NOCB kthread but this > happens after the last generic need_resched() check. Some cpuidle drivers > fix it by chance but many others don't. > > Here is a proposed bunch of fixes. I will need to also fix the > rcu_user_enter() case, likely using irq_work, since nohz_full requires > irq work to support self IPI. > > Also more generally, this raise the question of local task wake_up() > under disabled interrupts. When a wake up occurs in a preempt disabled > section, it gets handled by the outer preempt_enable() call. There is no > similar mechanism when a wake up occurs with interrupts disabled. I guess > it is assumed to be handled, at worst, in the next tick. But a local irq > work would provide instant preemption once IRQs are re-enabled. Of course > this would only make sense in CONFIG_PREEMPTION, and when the tick is > disabled... > > git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git > sched/idle > > HEAD: f2fa6e4a070c1535b9edc9ee097167fd2b15d235 > > Thanks, > Frederic > --- > > Frederic Weisbecker (4): > sched/idle: Fix missing need_resched() check after rcu_idle_enter() > cpuidle: Fix missing need_resched() check after rcu_idle_enter() > ARM: imx6q: Fix missing need_resched() check after rcu_idle_enter() > ACPI: processor: Fix missing need_resched() check after rcu_idle_enter() > > > arch/arm/mach-imx/cpuidle-imx6q.c | 7 ++++++- > drivers/acpi/processor_idle.c | 10 ++++++++-- > drivers/cpuidle/cpuidle.c | 33 +++++++++++++++++++++++++-------- > kernel/sched/idle.c | 18 ++++++++++++------ > 4 files changed, 51 insertions(+), 17 deletions(-)
Please feel free to add
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
to all patches in the series.
Thanks!
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