Hi,
I see that in 2.6.18-rt7 the rtmutex's wait_lock is sudden interrupt
disabling. I don't see the need as no (hard) interrupt-handlers should be
touching any mutex.
Esben
On Mon, 2006-10-23 at 11:55 +0200, Esben Nielsen wrote:
> Hi,
> I see that in 2.6.18-rt7 the rtmutex's wait_lock is sudden interrupt
> disabling. I don't see the need as no (hard) interrupt-handlers should be
> touching any mutex.
It does not touch mutexes, but the dynamic priority adjustment of the
hrtimer softirq needs it.
The correct solution will be moving the timer callback into the process
context, as it will be woken up anyway, but that's more complex to do
than it looks in the first place.
tglx
On Tue, 24 Oct 2006, Thomas Gleixner wrote:
> On Mon, 2006-10-23 at 11:55 +0200, Esben Nielsen wrote:
>> Hi,
>> I see that in 2.6.18-rt7 the rtmutex's wait_lock is sudden interrupt
>> disabling. I don't see the need as no (hard) interrupt-handlers should be
>> touching any mutex.
>
> It does not touch mutexes, but the dynamic priority adjustment of the
> hrtimer softirq needs it.
>
> The correct solution will be moving the timer callback into the process
> context, as it will be woken up anyway, but that's more complex to do
> than it looks in the first place.
>
I have send out patches doing the correct priority adjustment without
touching the wait_lock. Why not use that?
I found it in the archives:
http://www.uwsg.iu.edu/hypermail/linux/kernel/0610.0/0049.html
(or more specific in
http://www.uwsg.iu.edu/hypermail/linux/kernel/0610.0/0051.html, look for
changes to sched.c)
It is very bad to do PI traversal in interrupt context. In the general
case, where there are user-space locks, that operation unbounded. I
know that in your case you can only traverse kernel locks, but I think it
is bad to open for such posibilities if it can be avoided.
Esben
> tglx
>
>