[PATCH] fix problem with reschenduling in rest_init (2.6.35-rc3)

Ilya Loginov
2010-06-23T20:11:54Z

There is a bug in rest_init function. The problem is that kernel_init
thread starts before initialization of kthreadd_task when
CONFIG_PREEMPT_VOLUNTARY is enabled.

kernel_init thread do wake_up_process(kthreadd_task) and I have kernel Oops in
try_to_wake_up when I try to get p->state.

I found this problem on 2.6.34 on FPGA. It is very slow, and
find_task_by_pid is done after reschenduling. I have no this problem on
2.6.35-rc3 because kernel code is moved. But if I write simple loop like
volatile int tmp;
for(i = 0; i < preset_lpj; i++)
tmp++;
right after kernel_thread(kernel_init,.... , I have this problem on
2.6.35-rc3 too.

I understand that real problem is reschenduling in init code, but
I have no ability to fix it.

Signed-off-by: Ilya Loginov <isloginov@gmail.com>
---
diff --git a/init/main.c b/init/main.c
index 3bdb152..9febd69 100644
--- a/init/main.c
+++ b/init/main.c
@@ -428,12 +428,12 @@ static noinline void __init_refok rest_init(void)
int pid;

rcu_scheduler_starting();
- kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
numa_default_policy();
pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
rcu_read_lock();
kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
rcu_read_unlock();
+ kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
unlock_kernel();

/*