From: Michael Wang <[email protected]> With stop_machine() gone from the CPU offline path, we can't depend on preempt_disable() to prevent CPUs from going offline from under us.
Use the get/put_online_cpus_stable_atomic() APIs to prevent CPUs from going offline, while invoking from atomic context. [ Michael: Designed the synchronization for the IPI case ] Signed-off-by: Michael Wang <[email protected]> [ Srivatsa: Generalized it to work for all cases and wrote the changelog ] Signed-off-by: Srivatsa S. Bhat <[email protected]> --- kernel/smp.c | 54 +++++++++++++++++++++++++++++++++--------------------- 1 file changed, 33 insertions(+), 21 deletions(-) diff --git a/kernel/smp.c b/kernel/smp.c index 29dd40a..581727c 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -310,7 +310,8 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, * prevent preemption and reschedule on another processor, * as well as CPU removal */ - this_cpu = get_cpu(); + get_online_cpus_stable_atomic(); + this_cpu = smp_processor_id(); /* * Can deadlock when called with interrupts disabled. @@ -326,7 +327,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, func(info); local_irq_restore(flags); } else { - if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { + if ((unsigned)cpu < nr_cpu_ids && cpu_online_stable(cpu)) { struct call_single_data *data = &d; if (!wait) @@ -342,7 +343,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, } } - put_cpu(); + put_online_cpus_stable_atomic(); return err; } @@ -371,8 +372,10 @@ int smp_call_function_any(const struct cpumask *mask, const struct cpumask *nodemask; int ret; + get_online_cpus_stable_atomic(); /* Try for same CPU (cheapest) */ - cpu = get_cpu(); + cpu = smp_processor_id(); + if (cpumask_test_cpu(cpu, mask)) goto call; @@ -380,15 +383,15 @@ int smp_call_function_any(const struct cpumask *mask, nodemask = cpumask_of_node(cpu_to_node(cpu)); for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; cpu = cpumask_next_and(cpu, nodemask, mask)) { - if (cpu_online(cpu)) + if (cpu_online_stable(cpu)) goto call; } /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ - cpu = cpumask_any_and(mask, cpu_online_mask); + cpu = cpumask_any_and(mask, cpu_online_stable_mask); call: ret = smp_call_function_single(cpu, func, info, wait); - put_cpu(); + put_online_cpus_stable_atomic(); return ret; } EXPORT_SYMBOL_GPL(smp_call_function_any); @@ -409,14 +412,17 @@ void __smp_call_function_single(int cpu, struct call_single_data *data, unsigned int this_cpu; unsigned long flags; - this_cpu = get_cpu(); + get_online_cpus_stable_atomic(); + + this_cpu = smp_processor_id(); + /* * Can deadlock when called with interrupts disabled. * We allow cpu's that are not yet online though, as no one else can * send smp call function interrupt to this cpu and as such deadlocks * can't happen. */ - WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() + WARN_ON_ONCE(cpu_online(this_cpu) && wait && irqs_disabled() && !oops_in_progress); if (cpu == this_cpu) { @@ -427,7 +433,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *data, csd_lock(data); generic_exec_single(cpu, data, wait); } - put_cpu(); + put_online_cpus_stable_atomic(); } /** @@ -451,6 +457,8 @@ void smp_call_function_many(const struct cpumask *mask, unsigned long flags; int refs, cpu, next_cpu, this_cpu = smp_processor_id(); + get_online_cpus_stable_atomic(); + /* * Can deadlock when called with interrupts disabled. * We allow cpu's that are not yet online though, as no one else can @@ -461,23 +469,24 @@ void smp_call_function_many(const struct cpumask *mask, && !oops_in_progress && !early_boot_irqs_disabled); /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */ - cpu = cpumask_first_and(mask, cpu_online_mask); + cpu = cpumask_first_and(mask, cpu_online_stable_mask); if (cpu == this_cpu) - cpu = cpumask_next_and(cpu, mask, cpu_online_mask); + cpu = cpumask_next_and(cpu, mask, cpu_online_stable_mask); /* No online cpus? We're done. */ if (cpu >= nr_cpu_ids) - return; + goto out_unlock; /* Do we have another CPU which isn't us? */ - next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); + next_cpu = cpumask_next_and(cpu, mask, cpu_online_stable_mask); if (next_cpu == this_cpu) - next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); + next_cpu = cpumask_next_and(next_cpu, mask, + cpu_online_stable_mask); /* Fastpath: do that cpu by itself. */ if (next_cpu >= nr_cpu_ids) { smp_call_function_single(cpu, func, info, wait); - return; + goto out_unlock; } data = &__get_cpu_var(cfd_data); @@ -516,14 +525,14 @@ void smp_call_function_many(const struct cpumask *mask, smp_wmb(); /* We rely on the "and" being processed before the store */ - cpumask_and(data->cpumask, mask, cpu_online_mask); + cpumask_and(data->cpumask, mask, cpu_online_stable_mask); cpumask_clear_cpu(this_cpu, data->cpumask); refs = cpumask_weight(data->cpumask); /* Some callers race with other cpus changing the passed mask */ if (unlikely(!refs)) { csd_unlock(&data->csd); - return; + goto out_unlock; } raw_spin_lock_irqsave(&call_function.lock, flags); @@ -554,6 +563,9 @@ void smp_call_function_many(const struct cpumask *mask, /* Optionally wait for the CPUs to complete */ if (wait) csd_lock_wait(&data->csd); + +out_unlock: + put_online_cpus_stable_atomic(); } EXPORT_SYMBOL(smp_call_function_many); @@ -574,9 +586,9 @@ EXPORT_SYMBOL(smp_call_function_many); */ int smp_call_function(smp_call_func_t func, void *info, int wait) { - preempt_disable(); - smp_call_function_many(cpu_online_mask, func, info, wait); - preempt_enable(); + get_online_cpus_stable_atomic(); + smp_call_function_many(cpu_online_stable_mask, func, info, wait); + put_online_cpus_stable_atomic(); return 0; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
