lkml.org 
[lkml]   [2005]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Subject[RT] Race condition on bug output.
    From
    Date
    Hi Ingo,

    I found a race condition in my kernel which can also be found in yours.
    When I trigger the printk in check_periodic_interval, interrupts are
    turned on in release_console_sem. Unfortunately, this can have an
    interrupt go off there (since they are turned back on there) and the
    write_lock system_time_lock will be taken again, thus producing a
    deadlock.

    I'm not sure if this is the best solution, but this was the easiest.

    Maybe the CONFIG_PARANOID_GENERIC_TIME should be added in the warnings
    in init/main.c too?

    Since interrupts are kept off in the ktimer (hrtimer, whatever) in
    printk, this does not affect those patches. This is a PREEMPT_RT only
    problem.

    -- Steve

    Index: linux-2.6.14-rt22/kernel/printk.c
    ===================================================================
    --- linux-2.6.14-rt22.orig/kernel/printk.c 2005-12-06 21:44:53.000000000 -0500
    +++ linux-2.6.14-rt22/kernel/printk.c 2005-12-06 21:52:11.000000000 -0500
    @@ -757,7 +757,8 @@
    * on PREEMPT_RT, call console drivers with
    * interrupts enabled (unless we are debugging):
    */
    -#if defined(CONFIG_PREEMPT_RT) && !defined(CONFIG_PRINTK_IGNORE_LOGLEVEL) && !defined(CONFIG_PPC)
    +#if defined(CONFIG_PREEMPT_RT) && !defined(CONFIG_PRINTK_IGNORE_LOGLEVEL) && !defined(CONFIG_PPC) \
    + && !defined(CONFIG_PARANOID_GENERIC_TIME)
    spin_unlock_irq(&logbuf_lock);
    #else
    spin_unlock(&logbuf_lock);

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-12-07 04:37    [W:0.021 / U:123.036 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site