lkml.org 
[lkml]   [2013]   [Aug]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 5/8] rcu: eliminate deadlock for rcu read site
On Thu, 22 Aug 2013 10:34:31 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Thu, 22 Aug 2013 22:23:09 +0800
> Lai Jiangshan <eag0628@gmail.com> wrote:
>
>
> > > By making it a irq-safe lock, we need to disable interrupts every time
> > > it is taken, which means the entire pi-chain walk in
> > > rt_mutex_adjust_prio_chain() will pretty much be with interrupts
> > > disabled.
> >
> >
> > I didn't catch your meaning.
> > rt_mutex_adjust_prio_chain() is called without wait_lock held.
> > current C.S. of wait_lock are really short.
> >
>
> There is quite a bit of overhead to enable and disable interrupts. If
> we are doing this in a very fast path, it's going to slow down -rt even
> more.

Looking at the rt_mutex_adjust_prio_chain(), it's not that bad because
the pi_lock needs irqs disabled too, and we would just extend that
section.

But it still extends irqs off.

But in -rt, it is used in the rt_spin_lock_slowlock() where it can exit
out of the code without ever having to disable interrupts.

>
> It would be really nice to avoid making wait_lock be irq safe.

I still would like to exhaust other options before just making
wait_lock irq safe.

-- Steve


\
 
 \ /
  Last update: 2013-08-22 17:01    [W:0.226 / U:0.420 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site