linux-kernel - Re: [RFC 2/5] BKL: remove the BKL from kernel init code

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Date:	Wed, 02 Jun 2010 21:07:55 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	John Kacur <jkacur@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Jan Blunck <jblunck@...e.de>
Subject: Re: [RFC 2/5] BKL: remove the BKL from kernel init code

On Thu, 2010-06-03 at 02:13 +0200, Arnd Bergmann wrote:
> I have shown by code review that no driver takes
> the BKL at init time any more, so whatever the
> init code was locking against is no longer there
> and it is now safe to remove the BKL there.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  init/main.c          |    5 -----
>  kernel/trace/trace.c |    8 --------
>  2 files changed, 0 insertions(+), 13 deletions(-)
> 
> diff --git a/init/main.c b/init/main.c
> index 3bdb152..81821e1 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -434,7 +434,6 @@ static noinline void __init_refok rest_init(void)
>  	rcu_read_lock();
>  	kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
>  	rcu_read_unlock();
> -	unlock_kernel();
>  
>  	/*
>  	 * The boot idle thread must execute schedule()
> @@ -555,7 +554,6 @@ asmlinkage void __init start_kernel(void)
>   * Interrupts are still disabled. Do necessary setups, then
>   * enable them
>   */
> -	lock_kernel();
>  	tick_init();
>  	boot_cpu_init();
>  	page_address_init();
> @@ -819,7 +817,6 @@ static noinline int init_post(void)
>  	/* need to finish all async __init code before freeing the memory */
>  	async_synchronize_full();
>  	free_initmem();
> -	unlock_kernel();
>  	mark_rodata_ro();
>  	system_state = SYSTEM_RUNNING;
>  	numa_default_policy();
> @@ -855,8 +852,6 @@ static noinline int init_post(void)
>  
>  static int __init kernel_init(void * unused)
>  {
> -	lock_kernel();
> -
>  	/*
>  	 * init can allocate pages on any node
>  	 */
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 086d363..8047ca5 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -734,13 +734,6 @@ __acquires(kernel_lock)
>  		return -1;
>  	}
>  
> -	/*
> -	 * When this gets called we hold the BKL which means that
> -	 * preemption is disabled. Various trace selftests however
> -	 * need to disable and enable preemption for successful tests.
> -	 * So we drop the BKL here and grab it after the tests again.
> -	 */
> -	unlock_kernel();

Acked-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve

>  	mutex_lock(&trace_types_lock);
>  
>  	tracing_selftest_running = true;
> @@ -822,7 +815,6 @@ __acquires(kernel_lock)
>  #endif
>  
>   out_unlock:
> -	lock_kernel();
>  	return ret;
>  }
>  


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