lkml.org 
[lkml]   [2010]   [Feb]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 4/5] xtime_lock: Convert to raw_seqlock
On Thu, 18 Feb 2010, Peter Zijlstra wrote:

> On Wed, 2010-02-17 at 18:47 +0000, Thomas Gleixner wrote:
> >
> > xtime_lock needs a raw_spinlock in preempt-rt. Convert it to
> > raw_seqlock and fix up all users.
> >
> s/raw_spinlock/raw_seqlock/ ?
>
> Maybe add an explanation on _why_ -rt needs this for the uninformed
> amongst us.
>
> -rt switches to sleeping spinlocks, but since the vdso is basically
> userspace it cannot schedule, hence we need to keep using actual
> spinlocks (this is also the reason the vdso things must not call into
> lockdep)

No, the read_seq side is not taking the lock. It's just the write side
which is taking the spinlock to serialize against other writers.

xtime_lock is write locked in the timer interrupt context and therefor
cannot take a sleeping spinlock.

Thanks,

tglx


\
 
 \ /
  Last update: 2010-02-18 12:05    [W:0.207 / U:0.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site