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    Subject[PATCH 1/7] kgdb: Add the ability to schedule a breakpoint via a tasklet
    Date
    Some kgdb I/O modules require the ability to create a breakpoint
    tasklet, such as kgdboc and external modules such as kgdboe. The
    breakpoint tasklet is used as an asynchronous entry point into the
    debugger which will have a different function scope than the current
    execution path where it might not be safe to have an inline breakpoint
    inside the kgdb I/O driver.

    Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
    ---
    include/linux/kgdb.h | 1 +
    kernel/kgdb.c | 26 ++++++++++++++++++++++++++
    2 files changed, 27 insertions(+), 0 deletions(-)

    diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
    index 6adcc29..8fdd3cb 100644
    --- a/include/linux/kgdb.h
    +++ b/include/linux/kgdb.h
    @@ -279,5 +279,6 @@ extern int kgdb_nmicallback(int cpu, void *regs);

    extern int kgdb_single_step;
    extern atomic_t kgdb_active;
    +extern void kgdb_schedule_breakpoint(void);

    #endif /* _KGDB_H_ */
    diff --git a/kernel/kgdb.c b/kernel/kgdb.c
    index e4dcfb2..5365d46 100644
    --- a/kernel/kgdb.c
    +++ b/kernel/kgdb.c
    @@ -123,6 +123,7 @@ atomic_t kgdb_active = ATOMIC_INIT(-1);
    */
    static atomic_t passive_cpu_wait[NR_CPUS];
    static atomic_t cpu_in_kgdb[NR_CPUS];
    +static atomic_t kgdb_break_tasklet_var;
    atomic_t kgdb_setting_breakpoint;

    struct task_struct *kgdb_usethread;
    @@ -1623,6 +1624,31 @@ static void kgdb_unregister_callbacks(void)
    }
    }

    +/*
    + * There are times a tasklet needs to be used vs a compiled in in
    + * break point so as to cause an exception outside a kgdb I/O module,
    + * such as is the case with kgdboe, where calling a breakpoint in the
    + * I/O driver itself would be fatal.
    + */
    +static void kgdb_tasklet_bpt(unsigned long ing)
    +{
    + kgdb_breakpoint();
    + atomic_set(&kgdb_break_tasklet_var, 0);
    +}
    +
    +static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
    +
    +void kgdb_schedule_breakpoint(void)
    +{
    + if (atomic_read(&kgdb_break_tasklet_var) ||
    + atomic_read(&kgdb_active) != -1 ||
    + atomic_read(&kgdb_setting_breakpoint))
    + return;
    + atomic_inc(&kgdb_break_tasklet_var);
    + tasklet_schedule(&kgdb_tasklet_breakpoint);
    +}
    +EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
    +
    static void kgdb_initial_breakpoint(void)
    {
    kgdb_break_asap = 0;
    --
    1.6.0.2


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