2.6.15-rt4-sr1

2.6.15-rt4-sr1

[Steven Rostedt]

I've just uploaded my new maintenance release.

fixes:

- light soft lockup - currently it doesn't detect the light soft lockups
    because the counter was being reset in the wrong place.  Not sure if
    this was done earlier with some other issue.  But I needed this fix
    to get the low priority lockup to be detected.

- posix_timers deadlock - There's a loop in the posix_timeres code that 
    is entered if the current process is a higher priority than the 
    softirqd thread, and it spins until the softirqd thread is finished.
    But since the thread is of a higher priority than the softirqd, it
    deadlocks.

- read_trylock_rt  - added this for cases that have a loop on
    read_trylock.  Since in RT a read lock is a mutex, a read_trylock
    will fail even if the owner has it only for reading.  But since
    the reads are not protected with irqsaves, this can deadlock when
    a high priority process preempts the owner of the lock and spins
    till it's released. (this was seen in signal.c: send_group_sigqueue,
    there may be others)

Still at the normal location:

http://home.stny.rr.com/rostedt/patches/patch-2.6.15-rt4-sr1

Here is the program that showed all these nice deadlocks ;)

http://www.kihontech.com/tests/rt/timer_stress.c

(Run with -P to get the posix deadlocks)

-- Steve

Re: 2.6.15-rt4-sr1

[Thomas Gleixner]

On Wed, 2006-01-11 at 15:47 -0500, Steven Rostedt wrote:
> - posix_timers deadlock - There's a loop in the posix_timeres code that 
>     is entered if the current process is a higher priority than the 
>     softirqd thread, and it spins until the softirqd thread is finished.
>     But since the thread is of a higher priority than the softirqd, it
>     deadlocks.

Good catch, thanks

	tglx