|Subject:||[RFC/PATCH] FUSYN Realtime & robust mutexes for Linux try 2.2|
|Date:||Tue, 20 Apr 2004 21:03:26 -0700|
Hi All This is a new release of the code for providing a user and kernel space synchronization infrastructure that provides real-time friendly behavior, priority inversion protection (through serialized unlocks, priority inheritance and protection), deadlock detection and robustness. It builds upon the design of futexes and its usage model as NPTL does. Please look at the first patch, containing the documentation for information on how is it implemented. High level changelog since release 2.1: - Ported to 2.6.5 - Priority inheritance rework: now it should be fully functional: supports SCHED_NORMAL tasks, holding multiple mutexes (without bugs), ownership/wait chains with complex propagation rules and plays fine with the planned priority protection support. It required kind of invasive surgery at sched.c; need to find a way to simplify it as it is touching some very hot paths. - Added unserialized mode: in this mode, during unlocks, the mutex is not kept locked (this is how NPTL works). Performance increases, but you loose robustness guarantees. - Greg Weeks, from TimeSYS, provided the ports to ppc and ppc64; haven't tested myself as I lack such a machine. - Fix nasty bug when a signal is sent to a waiter--still can be improved. - Fix nastier bug in changing the priority of a waiter--can't call fuqueue_waiter_chprio() from inside a task_rq_lock/unlock pair or bad things might happen during priority inheritance (double spin lock). - Updated a wee bit the consistency() interface, now called ctl(), as it does way more than consistency control. Made the implementation a wee bit cleaner, still very ugly though. - Clean up some symbol names for correctness and meaning; wipe out some debugging stuff--still a lot left around, but will clean up IANF. Still to-do: - Requeue-like support for speeding up conditional variables. - Jamie's auto unlock-method detection. - Ugly bug triggered by running rtnptl-test-misc::str03 with: $ (ulimit -s 32; time ./str03 -b5 -d5 > /tmp/kk) [triggers inconsistency warning on NPTL patched with the rtnptl patch--haven't been able to reproduce it lately using the unserialized mode, but need to try with the serialized one again]. - Finish implementing priority protection; most of the infrastructure is there already. - Add a flag to the passing of timeout information to indicate if it is relative or absolute, and as we are there, the clock source. This way we avoid a costly kernel access in pthread_mutex_timelock() and friends. Plan to encapsulate the whole thing (timespec, rel/abs, clock source) in a struct copied from user space. - Wipe out debug stuff - research using single bit mode for fast-path on arches without compare-and-exchange but with test-and-set bit. - Call fuqueue_waiter_cancel() into try_to_wake_up? - Add CONFIG option to compile out parts or all. - Research more into safe static allocation as proposed by Scott Wood--the basic idea has a bunch of problems, mainly that it kills caching and some others, but needs further research. Did I miss anything? The patch is split in the following parts: 1/11: documentation files 2/11: modifications to the core 3/11: Support for i386 4/11: Support for ia64 5/11: Support for ppc 6/11: Support for ppc64 7/11: kernel fuqueues 8/11: user space/kernel space tracker 9/11: user space fuqueues 10/11: kernel fulocks 11/11: user space fulocks We have a site at http://developer.osdl.org/dev/robustmutexes with references to all the releases, test code and NPTL modifications (rtnptl) to use this code. As well, the patch is there in a single file, in case you don't want to paste them manually. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to firstname.lastname@example.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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