linux-kernel - Re: [BUG on PREEMPT_RT, 2.6.23.1-rt5] in rt-mutex code and signals

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Date:	Sat, 17 Nov 2007 09:55:40 -0800
From:	Daniel Walker <dwalker@...sta.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Remy Bohmer <linux@...mer.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	RT <linux-rt-users@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG on PREEMPT_RT, 2.6.23.1-rt5] in rt-mutex code and signals

On Sat, 2007-11-17 at 18:46 +0100, Ingo Molnar wrote:
> * Daniel Walker <dwalker@...sta.com> wrote:
> 
> > > Actually, IMO, compat_semaphores behave like semaphores should 
> > > behave, and thus the same as they behave on a non-RT kernel, and at 
> > > the locations where the semaphores are now misused as mutexes on RT, 
> > > we should replace them by differently-named-mutex-type-semaphores, 
> > > or better: real-RT-mutexes..
> > 
> > The vast majority of semaphore are actually binary semaphores in the 
> > Linux kernel .. So it's easier to mass convert semaphores to mutexes, 
> > then address the ones that don't conform.. Usually they are converted 
> > to the complete API in mainline..
> 
> right now there are 3992 mutex_lock() critical sections in the kernel 
> and only 351 down() based critical sections are left.
> 
> fixing the top 20:
> 
>       4 &vuart_bus_priv.probe_mutex
>       5 &connections_lock
>       5 &irq_ptr->setting_up_sema
>       5 &kbd->sem
>       5 &pnp_res_mutex
>       5 &port->port_lock
>       5 &tq_init_sem
>       6 &adb_handler_sem
>       6 &dev->parent->sem
>       6 &driver_lock
>       6 &ha->vport_sem
>       7 &big_buffer_sem
>       8 &dir_f->sem
>       9 &c->alloc_sem
>      11 &dev->sem
>      11 &usbvision->lock
>      12 &c->erase_free_sem
>      15 &u132->scheduler_lock
>      16 &zfcp_data.config_sema
>      17 &f->sem
> 
> would remove 164 of them, so it would convert half of the remaining 
> semaphore use in the kernel. So the job is almost finished - would 
> anyone like to go for the final grand feat: complete removal of 
> semaphores from the kernel? :-)

Sure, you want to split the list?

Daniel

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