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    Subject[PATCH] sched: Use show_regs() to improve __schedule_bug() output
    Hi Ingo,


    On Sun, 2 Sep 2007, Ingo Molnar wrote:
    >
    > Thanks! Not sure how that bug slipped in, in my tree it does this:
    >
    > + struct pt_regs *regs;
    > ...
    > + regs = get_irq_regs();

    You're very right indeed -- this bit was absent from -rc4-mm1's
    softlockup-improve-debug-output.patch but now that I looked at your
    original patch at http://lkml.org/lkml/2007/7/17/180, it becomes
    obvious this was simply a mismerge issue after all :-)

    [ Andrew, feel free to ignore my patch in case you just resolve
    the mismerge by yourself. ]


    BTW would something similar would be useful in __schedule_bug() too?
    I sure think so -- I'm not sure if EIP holds anything useful there,
    but CPU#, EFLAGS and the init_utsname() stuff would be definitely
    helpful ...


    [PATCH] sched: Use show_regs() to improve __schedule_bug() output

    A full register dump along with stack backtrace would make the "scheduling
    while atomic" message more helpful. Use show_regs() instead of dump_stack()
    for this. We already know we're atomic in here (that is why this function
    was called) so show_regs()'s atomicity expectations are guaranteed.

    Also, modify the output of the "BUG: scheduling while atomic:" header a bit
    to keep task->comm and task->pid together and preempt_count() after them.

    Signed-off-by: Satyam Sharma <satyam@infradead.org>

    ---

    kernel/sched.c | 14 +++++++++++---
    1 files changed, 11 insertions(+), 3 deletions(-)

    diff --git a/kernel/sched.c b/kernel/sched.c
    index b533d6d..4fb07c1 100644
    --- a/kernel/sched.c
    +++ b/kernel/sched.c
    @@ -63,6 +63,7 @@
    #include <linux/unistd.h>

    #include <asm/tlb.h>
    +#include <asm/irq_regs.h>

    /*
    * Scheduler clock - returns current time in nanosec units.
    @@ -3404,12 +3405,19 @@ EXPORT_SYMBOL(sub_preempt_count);
    */
    static noinline void __schedule_bug(struct task_struct *prev)
    {
    - printk(KERN_ERR "BUG: scheduling while atomic: %s/0x%08x/%d\n",
    - prev->comm, preempt_count(), prev->pid);
    + struct pt_regs *regs = get_irq_regs();
    +
    + printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
    + prev->comm, prev->pid, preempt_count());
    +
    debug_show_held_locks(prev);
    if (irqs_disabled())
    print_irqtrace_events(prev);
    - dump_stack();
    +
    + if (regs)
    + show_regs(regs);
    + else
    + dump_stack();
    }

    /*
    -
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      Last update: 2007-09-06 08:41    [W:0.023 / U:93.168 seconds]
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