[PATCH 1/2] cpu: hotplug: preserve per instance callback errors

[Bradley Morgan]

cpuhp_invoke_callback() unwinds earlier callbacks for the same
hotplug state when one instance fails. The rollback path currently
reuses ret, so a successful rollback can hide the original error and
make the failed transition look successful.

Keep the rollback result separate from the original error.

Fixes: 724a86881d03 ("smp/hotplug: Callback vs state-machine consistency")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Bradley Morgan <include@xxxxxxxxx>
---
 kernel/cpu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f975bb34915b..0f32086f9ed4 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -174,7 +174,7 @@ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
 	struct cpuhp_step *step = cpuhp_get_step(state);
 	int (*cbm)(unsigned int cpu, struct hlist_node *node);
 	int (*cb)(unsigned int cpu);
-	int ret, cnt;
+	int ret, cnt, rollback_ret;
 
 	if (st->fail == state) {
 		st->fail = CPUHP_INVALID;
@@ -238,12 +238,12 @@ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
 			break;
 
 		trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
-		ret = cbm(cpu, node);
-		trace_cpuhp_exit(cpu, st->state, state, ret);
+		rollback_ret = cbm(cpu, node);
+		trace_cpuhp_exit(cpu, st->state, state, rollback_ret);
 		/*
 		 * Rollback must not fail,
 		 */
-		WARN_ON_ONCE(ret);
+		WARN_ON_ONCE(rollback_ret);
 	}
 	return ret;
 }
-- 
2.53.0