diff --git a/drivers/char/random.c b/drivers/char/random.c index 8740f4215723..1b5b77bc202c 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -694,6 +694,25 @@ u32 get_random_u32(void) } EXPORT_SYMBOL(get_random_u32); +#ifdef CONFIG_SMP +/* + * This function is called when the CPU is coming up, with entry + * CPUHP_RANDOM_PREPARE, which comes before CPUHP_WORKQUEUE_PREP. + */ +int random_prepare_cpu(unsigned int cpu) +{ + /* + * When the cpu comes back online, immediately invalidate both + * the per-cpu crng and all batches, so that we serve fresh + * randomness. + */ + per_cpu_ptr(&crngs, cpu)->generation = ULONG_MAX; + per_cpu_ptr(&batched_entropy_u32, cpu)->position = UINT_MAX; + per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX; + return 0; +} +#endif + /** * randomize_page - Generate a random, page aligned address * @start: The smallest acceptable address the caller will take. @@ -1179,7 +1198,7 @@ struct fast_pool { }; struct work_struct mix; unsigned long last; - atomic_t count; + unsigned int count; u16 reg_idx; }; @@ -1215,6 +1234,29 @@ static void fast_mix(u32 pool[4]) static DEFINE_PER_CPU(struct fast_pool, irq_randomness); +#ifdef CONFIG_SMP +/* + * This function is called when the CPU has just come online, with + * entry CPUHP_AP_RANDOM_ONLINE, just after CPUHP_AP_WORKQUEUE_ONLINE. + */ +int random_online_cpu(unsigned int cpu) +{ + /* + * During CPU shutdown and before CPU onlining, add_interrupt_ + * randomness() may schedule mix_interrupt_randomness(), and + * set the MIX_INFLIGHT flag. However, because the worker can + * be scheduled on a different CPU during this period, that + * flag will never be cleared. For that reason, we zero out + * the flag here, which runs just after workqueues are onlined + * for the CPU again. This also has the effect of setting the + * irq randomness count to zero so that new accumulated irqs + * are fresh. + */ + per_cpu_ptr(&irq_randomness, cpu)->count = 0; + return 0; +} +#endif + static u32 get_reg(struct fast_pool *f, struct pt_regs *regs) { u32 *ptr = (u32 *)regs; @@ -1239,15 +1281,6 @@ static void mix_interrupt_randomness(struct work_struct *work) local_irq_disable(); if (fast_pool != this_cpu_ptr(&irq_randomness)) { local_irq_enable(); - /* - * If we are unlucky enough to have been moved to another CPU, - * during CPU hotplug while the CPU was shutdown then we set - * our count to zero atomically so that when the CPU comes - * back online, it can enqueue work again. The _release here - * pairs with the atomic_inc_return_acquire in - * add_interrupt_randomness(). - */ - atomic_set_release(&fast_pool->count, 0); return; } @@ -1256,7 +1289,7 @@ static void mix_interrupt_randomness(struct work_struct *work) * consistent view, before we reenable irqs again. */ memcpy(pool, fast_pool->pool32, sizeof(pool)); - atomic_set(&fast_pool->count, 0); + fast_pool->count = 0; fast_pool->last = jiffies; local_irq_enable(); @@ -1292,14 +1325,13 @@ void add_interrupt_randomness(int irq) } fast_mix(fast_pool->pool32); - /* The _acquire here pairs with the atomic_set_release in mix_interrupt_randomness(). */ - new_count = (unsigned int)atomic_inc_return_acquire(&fast_pool->count); + new_count = ++fast_pool->count; if (unlikely(crng_init == 0)) { if (new_count >= 64 && crng_pre_init_inject(fast_pool->pool32, sizeof(fast_pool->pool32), true, true) > 0) { - atomic_set(&fast_pool->count, 0); + fast_pool->count = 0; fast_pool->last = now; if (spin_trylock(&input_pool.lock)) { _mix_pool_bytes(&fast_pool->pool32, sizeof(fast_pool->pool32)); @@ -1317,7 +1349,7 @@ void add_interrupt_randomness(int irq) if (unlikely(!fast_pool->mix.func)) INIT_WORK(&fast_pool->mix, mix_interrupt_randomness); - atomic_or(MIX_INFLIGHT, &fast_pool->count); + fast_pool->count |= MIX_INFLIGHT; queue_work_on(raw_smp_processor_id(), system_highpri_wq, &fast_pool->mix); } EXPORT_SYMBOL_GPL(add_interrupt_randomness); diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 1ab0273560ae..8160ad1885dc 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -29,6 +29,7 @@ enum cpuhp_state { CPUHP_ACPI_CPUDRV_DEAD, CPUHP_S390_PFAULT_DEAD, CPUHP_BLK_MQ_DEAD, + CPUHP_RANDOM_PREPARE, CPUHP_WORKQUEUE_PREP, CPUHP_POWER_NUMA_PREPARE, CPUHP_HRTIMERS_PREPARE, @@ -119,6 +120,7 @@ enum cpuhp_state { CPUHP_AP_PERF_ARM_CCN_ONLINE, CPUHP_AP_PERF_ARM_L2X0_ONLINE, CPUHP_AP_WORKQUEUE_ONLINE, + CPUHP_AP_RANDOM_ONLINE, CPUHP_AP_RCUTREE_ONLINE, CPUHP_AP_NOTIFY_ONLINE, CPUHP_AP_ONLINE_DYN, diff --git a/include/linux/random.h b/include/linux/random.h index 0e6e9be97572..5598f8105eff 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -135,4 +135,9 @@ static inline bool __init arch_get_random_long_early(unsigned long *v) } #endif +#ifdef CONFIG_SMP +extern int random_prepare_cpu(unsigned int cpu); +extern int random_online_cpu(unsigned int cpu); +#endif + #endif /* _LINUX_RANDOM_H */ diff --git a/kernel/cpu.c b/kernel/cpu.c index e005209f279e..5ddac8914515 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -26,6 +26,7 @@ #include #include #include +#include #include #define CREATE_TRACE_POINTS @@ -1404,6 +1405,11 @@ static struct cpuhp_step cpuhp_bp_states[] = { .startup.single = perf_event_init_cpu, .teardown.single = perf_event_exit_cpu, }, + [CPUHP_RANDOM_PREPARE] = { + .name = "random:prepare", + .startup.single = random_prepare_cpu, + .teardown.single = NULL, + }, [CPUHP_WORKQUEUE_PREP] = { .name = "workqueue:prepare", .startup.single = workqueue_prepare_cpu, @@ -1529,6 +1535,11 @@ static struct cpuhp_step cpuhp_ap_states[] = { .startup.single = workqueue_online_cpu, .teardown.single = workqueue_offline_cpu, }, + [CPUHP_AP_RANDOM_ONLINE] = { + .name = "random:online", + .startup.single = random_online_cpu, + .teardown.single = NULL, + }, [CPUHP_AP_RCUTREE_ONLINE] = { .name = "RCU/tree:online", .startup.single = rcutree_online_cpu,