blocking, it registers a function and argument which are invoked
after all ongoing RCU read-side critical sections have completed.
This callback variant is particularly useful in situations where
- it is illegal to block.
+ it is illegal to block or where update-side performance is
+ critically important.
+
+ However, the call_rcu() API should not be used lightly, as use
+ of the synchronize_rcu() API generally results in simpler code.
+ In addition, the synchronize_rcu() API has the nice property
+ of automatically limiting update rate should grace periods
+ be delayed. This property results in system resilience in face
+ of denial-of-service attacks. Code using call_rcu() should limit
+ update rate in order to gain this same sort of resilience. See
+ checklist.txt for some approaches to limiting the update rate.
rcu_assign_pointer()
struct foo *new_fp;
struct foo *old_fp;
- new_fp = kmalloc(sizeof(*fp), GFP_KERNEL);
+ new_fp = kmalloc(sizeof(*new_fp), GFP_KERNEL);
spin_lock(&foo_mutex);
old_fp = gbl_foo;
*new_fp = *old_fp;
struct foo *new_fp;
struct foo *old_fp;
- new_fp = kmalloc(sizeof(*fp), GFP_KERNEL);
+ new_fp = kmalloc(sizeof(*new_fp), GFP_KERNEL);
spin_lock(&foo_mutex);
old_fp = gbl_foo;
*new_fp = *old_fp;
{
int cpu;
- for_each_cpu(cpu)
+ for_each_possible_cpu(cpu)
run_on(cpu);
}
RCU grace period:
- synchronize_kernel (deprecated)
synchronize_net
synchronize_sched
synchronize_rcu