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    SubjectRe: [patch] Real-Time Preemption, -RT-2.6.13-rc4-V0.7.52-01

    * Steven Rostedt <rostedt@goodmis.org> wrote:

    > Ingo,
    >
    > What's with the "BUG: possible soft lockup detected on CPU..."? I'm
    > getting a bunch of them from the IDE interrupt. It's not locking up,
    > but it does things that probably do take some time. Is this really
    > necessary? Here's an example dump:

    doh - it's Daniel not Cc:-ing lkml when sending me patches, so people
    dont know what's going on ...

    here's the patch below. Could you try to revert it?

    Ingo

    On Sun, 2005-07-31 at 20:27 +0200, Ingo Molnar wrote:
    > looks good, but i'd suggest to use printk_ratelimit(). (and the use of
    > u16 can be a performance hit on x86 due to potential 16-bit prefixes -
    > the best thing to use is an 'int' on pretty much every arch. with
    > printk_ratelimit() this flag go away anyway.)


    Ok, here's with your suggestions.


    Index: linux-2.6.12/kernel/softlockup.c
    ===================================================================
    --- linux-2.6.12.orig/kernel/softlockup.c 2005-07-31 15:31:09.000000000 +0000
    +++ linux-2.6.12/kernel/softlockup.c 2005-07-31 18:43:35.000000000 +0000
    @@ -9,6 +9,7 @@

    #include <linux/mm.h>
    #include <linux/cpu.h>
    +#include <linux/sched.h>
    #include <linux/init.h>
    #include <linux/delay.h>
    #include <linux/kthread.h>
    @@ -19,6 +20,7 @@ static DEFINE_RAW_SPINLOCK(print_lock);
    static DEFINE_PER_CPU(unsigned long, timeout) = INITIAL_JIFFIES;
    static DEFINE_PER_CPU(unsigned long, timestamp) = INITIAL_JIFFIES;
    static DEFINE_PER_CPU(unsigned long, print_timestamp) = INITIAL_JIFFIES;
    +static DEFINE_PER_CPU(struct task_struct *, prev_task);
    static DEFINE_PER_CPU(struct task_struct *, watchdog_task);

    static int did_panic = 0;
    @@ -56,6 +58,23 @@ void softlockup_tick(void)
    if (!per_cpu(watchdog_task, this_cpu))
    return;

    + if (per_cpu(prev_task, this_cpu) != current ||
    + !rt_task(current)) {
    + per_cpu(prev_task, this_cpu) = current;
    + }
    + else if (printk_ratelimit()) {
    +
    + spin_lock(&print_lock);
    + printk(KERN_ERR "BUG: possible soft lockup detected on CPU#%u! %lu-%lu(%lu)\n",
    + this_cpu, jiffies, timestamp, timeout);
    + dump_stack();
    +#if defined(__i386__) && defined(CONFIG_SMP)
    + nmi_show_all_regs();
    +#endif
    + spin_unlock(&print_lock);
    +
    + }
    +
    wake_up_process(per_cpu(watchdog_task, this_cpu));
    per_cpu(timeout, this_cpu) = jiffies + msecs_to_jiffies(1000);
    }
    @@ -71,7 +90,7 @@ void softlockup_tick(void)
    per_cpu(print_timestamp, this_cpu) = timestamp;

    spin_lock(&print_lock);
    - printk(KERN_ERR "BUG: soft lockup detected on CPU#%d! %ld-%ld(%ld)\n",
    + printk(KERN_ERR "BUG: soft lockup detected on CPU#%u! %lu-%lu(%lu)\n",
    this_cpu, jiffies, timestamp, timeout);
    dump_stack();
    #if defined(__i386__) && defined(CONFIG_SMP)
    -
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