Hi,

2012/5/2 Ivo Sieben [off-list ref]:

quoted

Hi,

Indeed the lock is only taken for a very short time. So  in most
situations it works fine, the lock is free, and can be taken quickly.
But when I stress my system (e.g. by continuously dumpling a lot of
text data to another serial terminal from the background), my high
priority task sometimes finds the lock is taken. In that case
additional lock handling comes in: priority inheritance, a context
switch to the background task that holds the lock, and a context
switch back after the lock is released again. This makes a normal read
that takes about 50us, to increase in execution time to 150us.

The PREEMPT_RT uses mutexes for "normal" spin locks that do not
disable interrupts...
I'll try to use raw spinlocks in this code section and for the tty flip buffer
See if that can solve my problem.

If you have other ideas... let me know!

Regards,
Ivo
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