Commit-ID: 60f53782c51f27c695840ce90c6c432284319eef
Gitweb: http://git.kernel.org/tip/60f53782c51f27c695840ce90c6c432284319eef
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Sat, 25 Aug 2012 15:27:40 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Sun, 23 Sep 2012 07:42:23 -0700
rcu: Prevent initialization race in rcutorture kthreads
When you do something like "t = kthread_run(...)", it is possible that
the kthread will start running before the assignment to "t" happens.
If the child kthread expects to find a pointer to its task_struct in "t",
it will then be fatally disappointed. This commit therefore switches
such cases to kthread_create() followed by wake_up_process(), guaranteeing
that the assignment happens before the child kthread starts running.
Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcutorture.c | 10 ++++++----
1 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 61be03b..aaa7b9f 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -2029,14 +2029,15 @@ rcu_torture_init(void)
/* Start up the kthreads. */
VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
- writer_task = kthread_run(rcu_torture_writer, NULL,
- "rcu_torture_writer");
+ writer_task = kthread_create(rcu_torture_writer, NULL,
+ "rcu_torture_writer");
if (IS_ERR(writer_task)) {
firsterr = PTR_ERR(writer_task);
VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
writer_task = NULL;
goto unwind;
}
+ wake_up_process(writer_task);
fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
GFP_KERNEL);
if (fakewriter_tasks == NULL) {
@@ -2151,14 +2152,15 @@ rcu_torture_init(void)
}
if (shutdown_secs > 0) {
shutdown_time = jiffies + shutdown_secs * HZ;
- shutdown_task = kthread_run(rcu_torture_shutdown, NULL,
- "rcu_torture_shutdown");
+ shutdown_task = kthread_create(rcu_torture_shutdown, NULL,
+ "rcu_torture_shutdown");
if (IS_ERR(shutdown_task)) {
firsterr = PTR_ERR(shutdown_task);
VERBOSE_PRINTK_ERRSTRING("Failed to create shutdown");
shutdown_task = NULL;
goto unwind;
}
+ wake_up_process(shutdown_task);
}
i = rcu_torture_onoff_init();
if (i != 0) {
--
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