On Sat, 6 Mar 2004, Adam Tla/lka wrote:
> On Sat, Mar 06, 2004 at 11:59:45AM +0100, Jaroslav Kysela wrote:
> > On Sat, 6 Mar 2004, Giuliano Pochini wrote:
> >
> > > On the Echoaudio cards the sample rate is a global setting, so I need a way
> > > to prevent an app to change the rate if someone else already set it (the
> > > card han several devices/subdevices). I was thinking to put a simple
> > > "if (IsAudioOpen()) rate_min=rate_max=current_rate;" in pcm_open callback,
> > > but this solution is racy.
> Talking about race conditions you could use a variable which is set to 0
> at the beginning. Now if app wants to set a rate it does atomic compare
> and increase (cmpxchg on x86) instruction so only one app could set
> rate. The other could only read memorized rate settins and report an
> error if rate is different.
We have already a number of locking features in kernel (spinlocks,
mutexes, atomic integer operations, atomic bitmap operations etc).
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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