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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-08-25 15:27:40 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-09-23 07:42:23 -0700
commit60f53782c51f27c695840ce90c6c432284319eef (patch)
treedaf20b20a35f09ecfa214127cf3c676f12c4edd1
parent2caa1e4432be7260dca60c3de6949b77eb007515 (diff)
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@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
-rw-r--r--kernel/rcutorture.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 61be03ba598d..aaa7b9f3532a 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) {