Messages in this thread | | | Date | Mon, 25 Oct 2004 12:40:23 +0200 | From | Ingo Molnar <> | Subject | [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0 |
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i have released the -V0 Real-Time Preemption patch, which can be downloaded from:
http://redhat.com/~mingo/realtime-preempt/
NOTE: this is a highly experimental release, a more experimental one than -U10.3.
the big change in the '-V' series of the patchset is that i have converted the last couple of non-preemptible kernel subsystems to fully-preemptible mutex-based locking. These subsystems are:
- the SLAB allocator - the buddy page allocator - waitqueue handling - soft-timer subsystem - security/selinux - workqueues - the random driver
this is probably the last 'big leap forward' in terms of the scope of the patch. (having reached the ultimate scope: it now encompasses everything ;)
But as an inevitable result of this big leap it will likely break in a couple of places. Unfortunately these subsystems were largely interdependent so it's an all-or-nothing step with not much middle ground between the locking done in -U10.3 and in -V0.
another result of these changes is that the number of critical sections in -V0 is roughly 30% of that in -U10.3. Now we only have the scheduler and very lowlevel IRQ-hardware locks as raw spinlocks. (plus the lone holdout vga_lock - which i will probably make a mutex too in the near future)
[ NOTE: there's one known bug in this release: selinux on one of my testsystems broke, it hangs during bootup. With CONFIG_SECURITY disabled it works fine. I'm working on the fix. So please keep CONFIG_SECURITY disabled for the time being. ]
other changes in -V0:
- build fixes: more driver fixes from Thomas Gleixner
- crash fix: fixed a bug found by Thomas Gleixner: rwsem runtime initialization was racy.
- deadlock fix: fixed lockup bug caused by __schedule clearing PREEMPT_ACTIVE. The need_resched loop is now outside of __schedule(). This might solve lockups/slowdowns reported by some people.
- latency fix: made keventd SCHED_FIFO - this could fix the mouse related delays reported by a number of people.
- latency fix: fixed SMP lock-break mechanism of mutexes.
- usability feature: hard-interrupts get decreasing SCHED_FIFO priority starting at prio 49 and stopping at prio 25. This should give a good default.
- debug feature: implemented SysRq-D to show the list of tasks with locks blocked on, if RW_SEM_DEADLOCK_DETECTION is enabled.
to create a -V0 tree from scratch, the patching order is:
http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.9.tar.bz2 + http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.9/2.6.9-mm1/2.6.9-mm1.bz2 + http://redhat.com/~mingo/realtime-preempt/realtime-preempt-2.6.9-mm1-V0
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