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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-08-04 06:10:23 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-09-07 16:27:22 -0700 |
| commit | 3f95aa81d265223fdb13ea2b59883766a05adbdf (patch) | |
| tree | 5b6d2c42aaf8b20397bd09c0ac31738618f57046 /kernel/exit.c | |
| parent | 53c6d4edf874d3cbc031a53738c6cba9277faea5 (diff) | |
| download | linux-3f95aa81d265223fdb13ea2b59883766a05adbdf.tar.gz linux-3f95aa81d265223fdb13ea2b59883766a05adbdf.tar.xz | |
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 <oleg@redhat.com>
Suggested-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/exit.c')
| -rw-r--r-- | kernel/exit.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 32c58f7433a3..d13f2eec4bb8 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -667,6 +667,7 @@ void do_exit(long code) { struct task_struct *tsk = current; int group_dead; + TASKS_RCU(int tasks_rcu_i); profile_task_exit(tsk); @@ -775,6 +776,7 @@ void do_exit(long code) */ flush_ptrace_hw_breakpoint(tsk); + TASKS_RCU(tasks_rcu_i = __srcu_read_lock(&tasks_rcu_exit_srcu)); exit_notify(tsk, group_dead); proc_exit_connector(tsk); #ifdef CONFIG_NUMA @@ -814,6 +816,7 @@ void do_exit(long code) if (tsk->nr_dirtied) __this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied); exit_rcu(); + TASKS_RCU(__srcu_read_unlock(&tasks_rcu_exit_srcu, tasks_rcu_i)); /* * The setting of TASK_RUNNING by try_to_wake_up() may be delayed |