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    SubjectRe: [ANNOUNCE] 2.6.15-rc5-hrt2 - hrtimers based high resolution patches
    Thomas and Ingo,

    I found a bug in 2.6.15-rc5-rt1 that was due to a race in the hrtimers
    code. This bug is most likely in the vanilla hrtimers code as well.

    I added a HRTIMER_RUNNING state because there's a moment in the
    run_hrtimer_queues that turns interrupts on and releases the base lock.
    In this time, a remove_hrtimer can be called while the state is still
    HRTIMER_PENDING_CALLBACK, but it has been removed off the list. The
    remove_hrtimer will then try to remove this again.

    Since I couldn't think of which state to use, I created the
    HRTIMER_RUNNING, and used that instead.

    I have a program (a simple jitter test) that, with out the patch,
    reliably crashes the 2.6.15-rc5-rt1 on a slow UP machine. With the
    patch, it runs solidly, so I know this is the reason for the crash.

    -- Steve

    Index: linux-2.6.15-rc5-rt1/kernel/hrtimer.c
    --- linux-2.6.15-rc5-rt1.orig/kernel/hrtimer.c 2005-12-13 15:51:52.000000000 -0500
    +++ linux-2.6.15-rc5-rt1/kernel/hrtimer.c 2005-12-13 15:53:36.000000000 -0500
    @@ -846,6 +846,7 @@
    data = timer->data;
    set_curr_timer(base, timer);
    + timer->state = HRTIMER_RUNNING;

    @@ -904,6 +905,7 @@
    data = timer->data;
    set_curr_timer(base, timer);
    __remove_hrtimer(timer, base);
    + timer->state = HRTIMER_RUNNING;

    Index: linux-2.6.15-rc5-rt1/include/linux/hrtimer.h
    --- linux-2.6.15-rc5-rt1.orig/include/linux/hrtimer.h 2005-12-13 15:51:40.000000000 -0500
    +++ linux-2.6.15-rc5-rt1/include/linux/hrtimer.h 2005-12-13 15:55:21.000000000 -0500
    @@ -41,6 +41,7 @@
    enum hrtimer_state {
    HRTIMER_INACTIVE, /* Timer is inactive */
    HRTIMER_EXPIRED, /* Timer is expired */
    + HRTIMER_RUNNING, /* Timer is currently running */
    HRTIMER_PENDING, /* Timer is pending */
    HRTIMER_PENDING_CALLBACK, /* Timer is expired, callback pending */

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      Last update: 2005-12-13 22:08    [W:0.029 / U:36.080 seconds]
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