From 3f95aa81d265223fdb13ea2b59883766a05adbdf Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 4 Aug 2014 06:10:23 -0700 Subject: [PATCH] rcu: Make TASKS_RCU handle tasks that are almost done exiting Once a task has passed exit_notify() in the do_exit() code path, it is no longer on the task lists, and is therefore no longer visible to rcu_tasks_kthread(). This means that an almost-exited task might be preempted while within a trampoline, and this task won't be waited on by rcu_tasks_kthread(). This commit fixes this bug by adding an srcu_struct. An exiting task does srcu_read_lock() just before calling exit_notify(), and does the corresponding srcu_read_unlock() after doing the final preempt_disable(). This means that rcu_tasks_kthread() can do synchronize_srcu() to wait for all mostly-exited tasks to reach their final preempt_disable() region, and then use synchronize_sched() to wait for those tasks to finish exiting. Reported-by: Oleg Nesterov Suggested-by: Lai Jiangshan Signed-off-by: Paul E. McKenney --- Reading git-format-patch failed