Hi folks!
I'm sorry to bother you, guys, but neither the mailing list
'[email protected]' nor Robert's address
'[email protected]' exist anymore.
If I have to address someone else, pls let me know.
We're currently investigating the locking of data structures in the
Linux Kernel -- namely 3.16.
Doing so, we've been logging every call to *lock() or *unlock(). For
further analysis, we log the preempt count as well.
Although we use a voluntary preemptive kernel
(defined(CONFIG_PREEMPT_VOLUNTARY) && !defined(CONFIG_PREEMPT) &&
!defined(CONFIG_PREEMPT_COUNT), the actual preemption count, the first
eight bits, aren't zero all time.
I'd expect the kernel to not touch those bits, because the
preempt_{enable,disable} functions do nearly nothing in my case.
They actually insert a memory barrier, but nothing more.
As you can see in the file (query.txt) attached to this mail, there are
several occasions where the preemption count is above zero. I'm a bit
puzzled why this happens...
The format is as follows:
The first three columns donate the position within the source code where
a lock has been acquired. The fourth column is the preemption count, as
returned by preemption_count(), after acquiring the lock.
The last column tells how often this happens.
I attached my kernel config as well.
Can you please tell why this happens?
Have I missed something? Might this be a bug?
Thanks!
Regards,
Alex
--
Technische Universität Dortmund
Alexander Lochmann PGP key: 0xBC3EF6FD
Otto-Hahn-Str. 16 phone: +49.231.7556141
D-44227 Dortmund fax: +49.231.7556116
http://ess.cs.tu-dortmund.de/Staff/al