Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 5/5] rcu: Prevent initialization race in rcutorture kthreads | Date | Thu, 30 Aug 2012 11:45:12 -0700 |
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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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> --- kernel/rcutorture.c | 10 ++++++---- 1 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 8ea2726..3e2adae 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -2028,14 +2028,15 @@ 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) { @@ -2150,14 +2151,15 @@ 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) { -- 1.7.8
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