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    SubjectRe: [PATCH] BUG(): sched.c: Line 944
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    On Tue, 2002-09-17 at 04:12, Robert Love wrote:

    > + if (unlikely(!kernel_locked()))
    > + tsk->lock_depth = -2;

    Eh, this should be likely()...

    Robert Love

    diff -urN linux-2.5.35/include/asm-i386/hardirq.h linux/include/asm-i386/hardirq.h
    --- linux-2.5.35/include/asm-i386/hardirq.h Sun Sep 15 22:18:46 2002
    +++ linux/include/asm-i386/hardirq.h Tue Sep 17 03:20:00 2002
    @@ -77,7 +77,8 @@
    #define irq_enter() (preempt_count() += HARDIRQ_OFFSET)

    #if CONFIG_PREEMPT
    -# define in_atomic() (preempt_count() != kernel_locked())
    +# define in_atomic() \
    + ((preempt_count() & ~PREEMPT_ACTIVE) != (current->lock_depth != -1))
    # define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1)
    #else
    # define in_atomic() (preempt_count() != 0)
    diff -urN linux-2.5.35/kernel/exit.c linux/kernel/exit.c
    --- linux-2.5.35/kernel/exit.c Tue Sep 17 03:18:53 2002
    +++ linux/kernel/exit.c Tue Sep 17 03:55:12 2002
    @@ -637,6 +637,21 @@
    preempt_disable();
    if (current->exit_signal == -1)
    release_task(current);
    +
    + /*
    + * This little bit of genius comes from the twisted mind of Linus.
    + * We need exit() to be atomic but we also want a debugging check
    + * in schedule() to whine if we are atomic. The wickedness is in
    + * these rules:
    + * - task->lock_depth = -2 means "validly nonpreemptable"
    + * - task->lock_depth = -1 means "BKL not held"
    + * - task->lock_depth >= 0 means "BKL held"
    + * release_kernel_lock and kernel_locked() check >=0, and
    + * in_atomic() checks != -1... the "fake BKL" will "cancel out"
    + * the preempt_disable() above and the world is happy.
    + */
    + if (likely(!kernel_locked()))
    + tsk->lock_depth = -2;
    schedule();
    BUG();
    /*
    diff -urN linux-2.5.35/kernel/sched.c linux/kernel/sched.c
    --- linux-2.5.35/kernel/sched.c Sun Sep 15 22:18:24 2002
    +++ linux/kernel/sched.c Tue Sep 17 03:50:04 2002
    @@ -940,8 +940,10 @@
    struct list_head *queue;
    int idx;

    - if (unlikely(in_atomic()))
    - BUG();
    + if (unlikely(in_atomic())) {
    + printk(KERN_ERR "error: scheduling while non-atomic!\n");
    + dump_stack();
    + }

    #if CONFIG_DEBUG_HIGHMEM
    check_highmem_ptes();
    @@ -959,7 +961,7 @@
    * if entering off of a kernel preemption go straight
    * to picking the next task.
    */
    - if (unlikely(preempt_count() & PREEMPT_ACTIVE))
    + if (unlikely(preempt_count() == PREEMPT_ACTIVE))
    goto pick_next_task;

    switch (prev->state) {
    -
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