Hi,
On Wed, May 6, 2020 at 9:42 AM Daniel Thompson
<daniel.thomp...@linaro.org> wrote:
>
> Currently there is a small window where a badly timed migration could
> cause in_dbg_master() to spuriously return true. Specifically if we
> migrate to a new core after reading the processor id and the previous
> core takes a breakpoint then we will evaluate true if we read
> kgdb_active before we get the IPI to bring us to halt.
>
> Fix this by checking irqs_disabled() first. Interrupts are always
> disabled when we are executing the kgdb trap so this is an acceptable
> prerequisite. This also allows us to replace raw_smp_processor_id()
> with smp_processor_id() since the short circuit logic will prevent
> warnings from PREEMPT_DEBUG.
>
> Fixes: dcc7871128e9 ("kgdb: core changes to support kdb")
> Suggested-by: Will Deacon <w...@kernel.org>
> Signed-off-by: Daniel Thompson <daniel.thomp...@linaro.org>
> ---
> include/linux/kgdb.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
> index b072aeb1fd78..4d6fe87fd38f 100644
> --- a/include/linux/kgdb.h
> +++ b/include/linux/kgdb.h
> @@ -323,7 +323,7 @@ extern void gdbstub_exit(int status);
> extern int kgdb_single_step;
> extern atomic_t kgdb_active;
> #define in_dbg_master() \
> - (raw_smp_processor_id() == atomic_read(&kgdb_active))
> + (irqs_disabled() && (smp_processor_id() == atomic_read(&kgdb_active)))
> extern bool dbg_is_early;
> extern void __init dbg_late_init(void);
> extern void kgdb_panic(const char *msg);
Reviewed-by: Douglas Anderson <diand...@chromium.org>
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