kdb: Avoid array subscript warnings on non-SMP builds

Recent versions of gcc (reported on gcc-7.4) issue array subscript
warnings for builds where SMP is not enabled.

kernel/debug/debug_core.c: In function 'kdb_dump_stack_on_cpu':
kernel/debug/debug_core.c:452:17: warning: array subscript is outside array
+bounds [-Warray-bounds]
     if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
           ~~~~~~~~~^~~~~
   kernel/debug/debug_core.c:469:33: warning: array subscript is outside array
+bounds [-Warray-bounds]
     kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
   kernel/debug/debug_core.c:470:18: warning: array subscript is outside array
+bounds [-Warray-bounds]
     while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)

There is no bug here but there is scope to improve the code
generation for non-SMP systems (whilst also silencing the warning).

Reported-by: kbuild test robot <lkp@intel.com>
Fixes: 2277b492582d ("kdb: Fix stack crawling on 'running' CPUs that aren't the master")
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20191021101057.23861-1-daniel.thompson@linaro.org
Reviewed-by: Douglas Anderson <dianders@chromium.org>

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 70e86b4b4932df083ce5c47b35f757c35431c773..2b7c9b67931d6818d85d5066544172f2df8693ac 100644 (file)
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -444,7 +444,7 @@ setundefined:
 #ifdef CONFIG_KGDB_KDB
 void kdb_dump_stack_on_cpu(int cpu)
 {
-       if (cpu == raw_smp_processor_id()) {
+       if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) {
                dump_stack();
                return;
        }