Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
authorLinus Torvalds <torvalds@linux-foundation.org>
Sun, 9 Sep 2018 13:48:06 +0000 (06:48 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sun, 9 Sep 2018 13:48:06 +0000 (06:48 -0700)
Pull cpu hotplug fixes from Thomas Gleixner:
 "Two fixes for the hotplug state machine code:

   - Move the misplaces smb() in the hotplug thread function to the
     proper place, otherwise a half update control struct could be
     observed

   - Prevent state corruption on error rollback, which causes the state
     to advance by one and as a consequence skip it in the bringup
     sequence"

* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu/hotplug: Prevent state corruption on error rollback
  cpu/hotplug: Adjust misplaced smb() in cpuhp_thread_fun()

kernel/cpu.c

index aa7fe85ad62e86de2060d2b89e525b93506cbf0d..0097acec1c717dee6948e50b57ab4c4bb0c15ac7 100644 (file)
@@ -607,15 +607,15 @@ static void cpuhp_thread_fun(unsigned int cpu)
        bool bringup = st->bringup;
        enum cpuhp_state state;
 
+       if (WARN_ON_ONCE(!st->should_run))
+               return;
+
        /*
         * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
         * that if we see ->should_run we also see the rest of the state.
         */
        smp_mb();
 
-       if (WARN_ON_ONCE(!st->should_run))
-               return;
-
        cpuhp_lock_acquire(bringup);
 
        if (st->single) {
@@ -916,7 +916,8 @@ static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
                if (ret) {
                        st->target = prev_state;
-                       undo_cpu_down(cpu, st);
+                       if (st->state < prev_state)
+                               undo_cpu_down(cpu, st);
                        break;
                }
        }
@@ -969,7 +970,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
         * to do the further cleanups.
         */
        ret = cpuhp_down_callbacks(cpu, st, target);
-       if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
+       if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
                cpuhp_reset_state(st, prev_state);
                __cpuhp_kick_ap(st);
        }