Revert "workqueue: allow work_on_cpu() to be called recursively"

This reverts commit c2fda509667b0fda4372a237f5a59ea4570b1627.

c2fda509667b removed lockdep annotation from work_on_cpu() to work around
the PCI path that calls work_on_cpu() from within a work_on_cpu() work item
(PF driver .probe() method -> pci_enable_sriov() -> add VFs -> VF driver
.probe method).

961da7fb6b22 ("PCI: Avoid unnecessary CPU switch when calling driver
.probe() method) avoids that recursive work_on_cpu() use in a different
way, so this revert restores the work_on_cpu() lockdep annotation.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Tejun Heo <tj@kernel.org>

1 files changed, 10 insertions, 22 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 987293d03ebc..5690b8eabfbc 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2840,19 +2840,6 @@ already_gone:
         return false;
 }
 
-static bool __flush_work(struct work_struct *work)
-{
-        struct wq_barrier barr;
-
-        if (start_flush_work(work, &barr)) {
-                wait_for_completion(&barr.done);
-                destroy_work_on_stack(&barr.work);
-                return true;
-        } else {
-                return false;
-        }
-}
-
 /**
  * flush_work - wait for a work to finish executing the last queueing instance
  * @work: the work to flush
@@ -2866,10 +2853,18 @@ static bool __flush_work(struct work_struct *work)
  */
 bool flush_work(struct work_struct *work)
 {
+        struct wq_barrier barr;
+
         lock_map_acquire(&work->lockdep_map);
         lock_map_release(&work->lockdep_map);
 
-        return __flush_work(work);
+        if (start_flush_work(work, &barr)) {
+                wait_for_completion(&barr.done);
+                destroy_work_on_stack(&barr.work);
+                return true;
+        } else {
+                return false;
+        }
 }
 EXPORT_SYMBOL_GPL(flush_work);
 
@@ -4814,14 +4809,7 @@ long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
 
         INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
         schedule_work_on(cpu, &wfc.work);
-
-        /*
-         * The work item is on-stack and can't lead to deadlock through
-         * flushing.  Use __flush_work() to avoid spurious lockdep warnings
-         * when work_on_cpu()s are nested.
-         */
-        __flush_work(&wfc.work);
-
+        flush_work(&wfc.work);
         return wfc.ret;
 }
 EXPORT_SYMBOL_GPL(work_on_cpu);