Once stop_machine() is gone from the CPU offline path, we won't be able to depend on disabling preemption to prevent CPUs from going offline from under us.
Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, while invoking from atomic context. Cc: Al Viro <[email protected]> Cc: Tejun Heo <[email protected]> Signed-off-by: Srivatsa S. Bhat <[email protected]> --- lib/percpu_counter.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index ba6085d..f5e718d 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -98,6 +98,15 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc) s64 ret; int cpu; + /* + * The calls to get/put_online_cpus_atomic() is strictly not + * necessary, since CPU hotplug is explicitly handled via the + * hotplug callback which synchronizes through fbc->lock. + * But we add them here anyway to make it easier for the debug + * code under CONFIG_DEBUG_HOTPLUG_CPU to validate the correctness + * of hotplug synchronization. + */ + get_online_cpus_atomic(); raw_spin_lock(&fbc->lock); ret = fbc->count; for_each_online_cpu(cpu) { @@ -105,6 +114,7 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc) ret += *pcount; } raw_spin_unlock(&fbc->lock); + put_online_cpus_atomic(); return ret; } EXPORT_SYMBOL(__percpu_counter_sum); -- 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/
