Re: [PATCH [RT] 11/14] optimize the !printk fastpath through the lock acquisition

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To: Gregory Haskins <ghaskins@...>

Cc: <mingo@...>, <a.p.zijlstra@...>, <tglx@...>, <rostedt@...>, <linux-rt-users@...>, <linux-kernel@...>, <bill.huey@...>, <kevin@...>, <cminyard@...>, <dsingleton@...>, <dwalker@...>, <npiggin@...>, <dsaxena@...>, <gregkh@...>, <sdietrich@...>, <pmorreale@...>, <mkohari@...>

Subject: Re: [PATCH [RT] 11/14] optimize the !printk fastpath through the lock acquisition

Date: Thursday, February 21, 2008 - 12:36 pm

On Thursday 21 February 2008 16:27:22 Gregory Haskins wrote:

quoted text> @@ -660,12 +660,12 @@ rt_spin_lock_fastlock(struct rt_mutex *lock,
>  		void fastcall (*slowfn)(struct rt_mutex *lock))
>  {
>  	/* Temporary HACK! */
> -	if (!current->in_printk)
> -		might_sleep();
> -	else if (in_atomic() || irqs_disabled())
> +	if (unlikely(current->in_printk) && (in_atomic() || irqs_disabled()))

I have my doubts that gcc will honor unlikelies that don't affect
the complete condition of an if.

Also conditions guarding returns are by default predicted unlikely
anyways AFAIK. 

The patch is likely a nop.

-Andi
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Messages in current thread:

[PATCH [RT] 00/14] RFC - adaptive real-time locks, Gregory Haskins, (Thu Feb 21, 11:26 am)

Re: [PATCH [RT] 00/14] RFC - adaptive real-time locks, Ingo Molnar, (Thu Feb 21, 5:24 pm)

Re: [PATCH [RT] 00/14] RFC - adaptive real-time locks, Andrew Morton, (Sat Feb 23, 4:03 am)

Re: [PATCH [RT] 00/14] RFC - adaptive real-time locks, Peter W. Morreale, (Thu Feb 21, 6:12 pm)

Re: [PATCH [RT] 00/14] RFC - adaptive real-time locks, Peter W. Morreale, (Thu Feb 21, 6:42 pm)

Re: [PATCH [RT] 00/14] RFC - adaptive real-time locks, Gregory Haskins, (Thu Feb 21, 5:40 pm)

Re: [PATCH [RT] 00/14] RFC - adaptive real-time locks, Bill Huey (hui), (Thu Feb 21, 5:33 pm)

Re: [PATCH [RT] 00/14] RFC - adaptive real-time locks, Gregory Haskins, (Thu Feb 21, 12:05 pm)

[PATCH [RT] 14/14] sysctl for runtime-control of lateral mut..., Gregory Haskins, (Thu Feb 21, 11:27 am)

[PATCH [RT] 13/14] allow rt-mutex lock-stealing to include l..., Gregory Haskins, (Thu Feb 21, 11:27 am)

[PATCH [RT] 12/14] remove the extra call to try_to_take_lock, Gregory Haskins, (Thu Feb 21, 11:27 am)

[PATCH [RT] 11/14] optimize the !printk fastpath through the..., Gregory Haskins, (Thu Feb 21, 11:27 am)

Re: [PATCH [RT] 11/14] optimize the !printk fastpath through..., Pavel Machek, (Fri Feb 22, 3:18 pm)

Re: [PATCH [RT] 11/14] optimize the !printk fastpath through..., Gregory Haskins, (Fri Feb 22, 6:20 pm)

Re: [PATCH [RT] 11/14] optimize the !printk fastpath through..., Bill Huey (hui), (Fri Feb 22, 8:43 pm)

Re: [PATCH [RT] 11/14] optimize the !printk fastpath through..., Gregory Haskins, (Mon Feb 25, 1:20 am)

Re: [PATCH [RT] 11/14] optimize the !printk fastpath through..., Bill Huey (hui), (Mon Feb 25, 2:21 am)

Re: [PATCH [RT] 11/14] optimize the !printk fastpath through..., Bill Huey (hui), (Mon Feb 25, 5:02 am)

Re: [PATCH [RT] 11/14] optimize the !printk fastpath through..., Andi Kleen, (Thu Feb 21, 12:36 pm)

Re: [PATCH [RT] 11/14] optimize the !printk fastpath through..., Gregory Haskins, (Thu Feb 21, 12:47 pm)

[PATCH [RT] 10/14] adjust pi_lock usage in wakeup, Gregory Haskins, (Thu Feb 21, 11:27 am)

Re: [PATCH [RT] 10/14] adjust pi_lock usage in wakeup, Steven Rostedt, (Thu Feb 21, 12:48 pm)

Re: [PATCH [RT] 10/14] adjust pi_lock usage in wakeup, Peter W. Morreale, (Thu Feb 21, 1:09 pm)

[PATCH [RT] 09/14] adaptive mutexes, Gregory Haskins, (Thu Feb 21, 11:27 am)

[PATCH [RT] 08/14] add a loop counter based timeout mechanism, Gregory Haskins, (Thu Feb 21, 11:27 am)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Andi Kleen, (Thu Feb 21, 12:41 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Paul E. McKenney, (Fri Feb 22, 3:08 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Bill Huey (hui), (Fri Feb 22, 3:19 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Bill Huey (hui), (Fri Feb 22, 3:21 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Paul E. McKenney, (Fri Feb 22, 3:43 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Peter W. Morreale, (Fri Feb 22, 4:15 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Sven-Thorsten Dietrich, (Fri Feb 22, 3:55 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Peter W. Morreale, (Fri Feb 22, 4:36 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Sven-Thorsten Dietrich, (Sat Feb 23, 3:36 am)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Paul E. McKenney, (Fri Feb 22, 4:23 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Gregory Haskins, (Fri Feb 22, 6:03 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Andi Kleen, (Sat Feb 23, 8:31 am)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Paul E. McKenney, (Sat Feb 23, 12:32 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Sven-Thorsten Dietrich, (Thu Feb 21, 1:06 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Peter W. Morreale, (Thu Feb 21, 1:04 pm)

Re: [PATCH [RT] 08/14] add a loop counter based timeout mech..., Gregory Haskins, (Thu Feb 21, 1:02 pm)

[PATCH [RT] 07/14] adaptive real-time lock support, Gregory Haskins, (Thu Feb 21, 11:27 am)

Re: [PATCH [RT] 07/14] adaptive real-time lock support, Pavel Machek, (Fri Feb 22, 3:14 pm)

[PATCH [RT] 06/14] optimize rt lock wakeup, Gregory Haskins, (Thu Feb 21, 11:26 am)

[PATCH [RT] 05/14] rearrange rt_spin_lock sleep, Gregory Haskins, (Thu Feb 21, 11:26 am)

Re: [PATCH [RT] 05/14] rearrange rt_spin_lock sleep, Gregory Haskins, (Fri Feb 22, 9:29 am)

Re: [PATCH [RT] 05/14] rearrange rt_spin_lock sleep, Ingo Molnar, (Fri Feb 22, 9:35 am)

Re: [PATCH [RT] 05/14] rearrange rt_spin_lock sleep, Steven Rostedt, (Fri Feb 22, 9:46 am)

Re: [PATCH [RT] 05/14] rearrange rt_spin_lock sleep, Steven Rostedt, (Fri Feb 22, 9:43 am)

Re: [PATCH [RT] 05/14] rearrange rt_spin_lock sleep, Steven Rostedt, (Fri Feb 22, 9:35 am)

Re: [PATCH [RT] 05/14] rearrange rt_spin_lock sleep, Peter Zijlstra, (Fri Feb 22, 9:40 am)

[PATCH [RT] 04/14] disable PREEMPT_SPINLOCK_WAITERS when x86..., Gregory Haskins, (Thu Feb 21, 11:26 am)

[PATCH [RT] 03/14] x86: FIFO ticket spinlocks, Gregory Haskins, (Thu Feb 21, 11:26 am)

[PATCH [RT] 02/14] spinlock: make preemptible-waiter feature..., Gregory Haskins, (Thu Feb 21, 11:26 am)

Re: [PATCH [RT] 02/14] spinlock: make preemptible-waiter fea..., Pavel Machek, (Fri Feb 22, 3:09 pm)

[PATCH [RT] 01/14] spinlocks: fix preemption feature when PR..., Gregory Haskins, (Thu Feb 21, 11:26 am)

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