* Mike Travis <tra...@sgi.com> wrote:
> This patch adds a kgdb_nmicallin() interface that can be used by
> external NMI handlers to call the KGDB/KDB handler. The primary need
> for this is for those types of NMI interrupts where all the CPUs
> have already received the NMI signal. Therefore no send_IPI(NMI)
> is required, and in fact it will cause a 2nd unhandled NMI to occur.
> This generates the "Dazed and Confuzed" messages.
>
> Since all the CPUs are getting the NMI at roughly the same time, it's not
> guaranteed that the first CPU that hits the NMI handler will manage to
> enter KGDB and set the dbg_master_lock before the slaves start entering.
> The new argument "send_ready" was added for KGDB to signal the NMI handler
> to release the slave CPUs for entry into KGDB.
>
> Signed-off-by: Mike Travis <tra...@sgi.com>
> Reviewed-by: Dimitri Sivanich <sivan...@sgi.com>
> Reviewed-by: Hedi Berriche <h...@sgi.com>
> Acked-by: Jason Wessel <jason.wes...@windriver.com>
> ---
> v3: make entry into SYSTEM_NMI section more specific
> ---
> include/linux/kdb.h | 1 +
> include/linux/kgdb.h | 1 +
> kernel/debug/debug_core.c | 30 +++++++++++++++++++++++++++++-
> kernel/debug/debug_core.h | 1 +
> kernel/debug/kdb/kdb_debugger.c | 5 ++++-
> kernel/debug/kdb/kdb_main.c | 3 +++
> 6 files changed, 39 insertions(+), 2 deletions(-)
>
> --- linux.orig/include/linux/kdb.h
> +++ linux/include/linux/kdb.h
> @@ -109,6 +109,7 @@ typedef enum {
> KDB_REASON_RECURSE, /* Recursive entry to kdb;
> * regs probably valid */
> KDB_REASON_SSTEP, /* Single Step trap. - regs valid */
> + KDB_REASON_SYSTEM_NMI, /* In NMI due to SYSTEM cmd; regs valid */
> } kdb_reason_t;
Note that this is within an #ifdef CONFIG_KGDB_KDB section.
> --- linux.orig/kernel/debug/debug_core.c
> +++ linux/kernel/debug/debug_core.c
> @@ -575,8 +575,12 @@ return_normal:
> raw_spin_lock(&dbg_slave_lock);
>
> #ifdef CONFIG_SMP
> + /* If SYSTEM_NMI, slaves are already waiting */
> + if (ks->err_code == KDB_REASON_SYSTEM_NMI)
> + atomic_set(ks->send_ready, 1);
And this then fails to build if CONFIG_KGDB_KDB is turned off:
kernel/debug/debug_core.c:579:22: error: ‘KDB_REASON_SYSTEM_NMI’ undeclared
(first use in this function)
kernel/debug/debug_core.c:753:19: error: ‘KDB_REASON_SYSTEM_NMI’ undeclared
(first use in this function)
More fundamentally, I think the way KDB internals added to debug_core.c by
this patch violates its relatively layered design.
It would be cleaner to add helper functions defined in kdb and turned into
empty inlines in the !CONFIG_KGDB_KDB case, like it's done for a couple of
other cases in kdb.h:
static inline void kdb_init(int level) {}
static inline int kdb_register(char *cmd, kdb_func_t func, char *usage,
char *help, short minlen) { return 0; }
static inline int kdb_register_repeat(char *cmd, kdb_func_t func, char *usage,
char *help, short minlen,
kdb_repeat_t repeat) { return 0; }
static inline int kdb_unregister(char *cmd) { return 0; }
So this needs more work.
Thanks,
Ingo
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