Messages in this thread Patch in this message | | | Date | Thu, 26 Mar 2020 17:32:44 +0100 | Subject | [PATCH 1/2] irq_work: Reinitialize list heads for secondary CPUs | From | Jann Horn <> |
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When printk_deferred() is used before percpu initialization, it will queue up lazy IRQ work on the boot CPU; percpu initialization then copies the work list head to all secondary CPUs. To ensure that the secondary CPUs don't re-execute the boot CPU's work and whatever its ->next pointer leads to, zero out the secondary CPUs' work list heads before bringing up SMP.
Signed-off-by: Jann Horn <jannh@google.com> --- kernel/irq_work.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/kernel/irq_work.c b/kernel/irq_work.c index 828cc30774bc..903e5be9aebf 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -152,6 +152,7 @@ static void irq_work_run_list(struct llist_head *list) * while we are in the middle of the func. */ flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags); + WARN_ON_ONCE((flags & IRQ_WORK_PENDING) == 0); work->func(work); /* @@ -195,3 +196,24 @@ void irq_work_sync(struct irq_work *work) cpu_relax(); } EXPORT_SYMBOL_GPL(irq_work_sync); + +/* + * If we queued up IRQ work before fully initializing the percpu subsystem, e.g. + * via printk_deferred(), the head pointer of the boot CPU will have been copied + * over to all the other CPUs. + * To fix that, manually initialize the list heads of all secondary processors + * before bringing up SMP. + */ +static int __init irq_work_percpu_fixup(void) +{ + int cpu; + + for_each_possible_cpu(cpu) { + if (cpu == smp_processor_id()) + continue; + per_cpu(raised_list.first, cpu) = NULL; + per_cpu(lazy_list.first, cpu) = NULL; + } + return 0; +} +early_initcall(irq_work_percpu_fixup) -- 2.25.1.696.g5e7596f4ac-goog
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