Subject: Re: [linux-audio-dev] priority inversion & inheritance
From: Peter Hanappe (peter_AT_hanappe.com)
Date: Fri Jul 12 2002 - 11:31:14 EEST
yodaiken_AT_fsmlabs.com wrote:
> On Fri, Jul 12, 2002 at 01:40:42AM +0200, Peter Hanappe wrote:
>
>>yodaiken_AT_fsmlabs.com wrote:
>>
>>
>>>For example, in RTLinux, fifos shared
>>>between Linux (non-rt) processes and RT threads are asymmetric: the
>>>RT thread never blocks, the non-RT thread blocks. In many cases
>>>it is best to optimize the data operations and perform them under
>>>a spin_lock with interrupts disabled. In RTLinux pthread_spin_lock
>>>disables irqs and, in SMP also sets the lock
>>> pthread_spin_lock(&myq.spin);
>>> myq.tail->next = new;
>>> new->next = 0;
>>> myq.tail= next;
>>> if(!myq.head)myq.head = new;
>>> pthread_spin_unlock(&myq.spin);
>>>
>>How do you tell a blocking non-RT thread that new data is available?
>>
>
> It's done automatically by a write: a write does sends a soft interrupt to
> Linux and the interrupt handler does a standard wakeup on flagged fifos.
This wakeup doesn't involve a call to the scheduler?
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