On 1/4/2016 5:52 PM, Steven Rostedt wrote:
On Mon, 4 Jan 2016 14:34:44 -0500 Chris Metcalf<cmetcalf@xxxxxxxxxx> wrote:>+#ifdef CONFIG_TASK_ISOLATION >+void task_isolation_debug(int cpu) >+{ >+ struct task_struct *p; >+ >+ if (!task_isolation_possible(cpu)) >+ return; >+ >+ rcu_read_lock();What's the rcu_read_lock() for? I don't see what is being protected by rcu here?
I'm not completely clear either, but this is the same idiom as is used throughout kernel/sched/core.c when mapping from a pid or a cpu to a task_struct, since obviously you could end up racing with the task_struct being removed after the task dies. My best understanding is that the rcu_read_lock() holds up the final free of the structure so that we have time here to get another reference to it. See for example sched_setaffinity() for a similar use of the idiom. -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
