SLOW_WORK: Fix the CONFIG_MODULES=n case

Commits 3d7a641 ("SLOW_WORK: Wait for outstanding work items belonging to a
module to clear") introduced some code to make sure that all of a module's
slow-work items were complete before that module was removed, and commit
3bde31a ("SLOW_WORK: Allow a requeueable work item to sleep till the thread is
needed") further extended that, breaking it in the process if CONFIG_MODULES=n:

    CC      kernel/slow-work.o
  kernel/slow-work.c: In function 'slow_work_execute':
  kernel/slow-work.c:313: error: 'slow_work_thread_processing' undeclared (first use in this function)
  kernel/slow-work.c:313: error: (Each undeclared identifier is reported only once
  kernel/slow-work.c:313: error: for each function it appears in.)
  kernel/slow-work.c: In function 'slow_work_wait_for_items':
  kernel/slow-work.c:950: error: 'slow_work_unreg_sync_lock' undeclared (first use in this function)
  kernel/slow-work.c:951: error: 'slow_work_unreg_wq' undeclared (first use in this function)
  kernel/slow-work.c:961: error: 'slow_work_unreg_work_item' undeclared (first use in this function)
  kernel/slow-work.c:974: error: 'slow_work_unreg_module' undeclared (first use in this function)
  kernel/slow-work.c:977: error: 'slow_work_thread_processing' undeclared (first use in this function)
  make[1]: *** [kernel/slow-work.o] Error 1

Fix this by:

 (1) Extracting the bits of slow_work_execute() that are contingent on
     CONFIG_MODULES, and the bits that should be, into inline functions and
     placing them into the #ifdef'd section that defines the relevant variables
     and adding stubs for moduleless kernels.  This allows the removal of some
     #ifdefs.

 (2) #ifdef'ing out the contents of slow_work_wait_for_items() in moduleless
     kernels.

The four functions related to handling module unloading synchronisation (and
their associated variables) could be offloaded into a separate .c file, but
each function is only used once and three of them are tiny, so doing so would
prevent them from being inlined.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 29 insertions, 17 deletions

diff --git a/kernel/slow-work.c b/kernel/slow-work.c
index da94f3c101af..b5c17f15f9de 100644
--- a/kernel/slow-work.c
+++ b/kernel/slow-work.c
@@ -109,6 +109,30 @@ static struct module *slow_work_unreg_module;
 static struct slow_work *slow_work_unreg_work_item;
 static DECLARE_WAIT_QUEUE_HEAD(slow_work_unreg_wq);
 static DEFINE_MUTEX(slow_work_unreg_sync_lock);
+
+static void slow_work_set_thread_processing(int id, struct slow_work *work)
+{
+        if (work)
+                slow_work_thread_processing[id] = work->owner;
+}
+static void slow_work_done_thread_processing(int id, struct slow_work *work)
+{
+        struct module *module = slow_work_thread_processing[id];
+
+        slow_work_thread_processing[id] = NULL;
+        smp_mb();
+        if (slow_work_unreg_work_item == work ||
+            slow_work_unreg_module == module)
+                wake_up_all(&slow_work_unreg_wq);
+}
+static void slow_work_clear_thread_processing(int id)
+{
+        slow_work_thread_processing[id] = NULL;
+}
+#else
+static void slow_work_set_thread_processing(int id, struct slow_work *work) {}
+static void slow_work_done_thread_processing(int id, struct slow_work *work) {}
+static void slow_work_clear_thread_processing(int id) {}
 #endif
 
 /*
@@ -197,9 +221,6 @@ static unsigned slow_work_calc_vsmax(void)
  */
 static noinline bool slow_work_execute(int id)
 {
-#ifdef CONFIG_MODULES
-        struct module *module;
-#endif
         struct slow_work *work = NULL;
         unsigned vsmax;
         bool very_slow;
@@ -236,10 +257,7 @@ static noinline bool slow_work_execute(int id)
                 very_slow = false; /* avoid the compiler warning */
         }
 
-#ifdef CONFIG_MODULES
-        if (work)
-                slow_work_thread_processing[id] = work->owner;
-#endif
+        slow_work_set_thread_processing(id, work);
         if (work) {
                 slow_work_mark_time(work);
                 slow_work_begin_exec(id, work);
@@ -287,15 +305,7 @@ static noinline bool slow_work_execute(int id)
 
         /* sort out the race between module unloading and put_ref() */
         slow_work_put_ref(work);
-
-#ifdef CONFIG_MODULES
-        module = slow_work_thread_processing[id];
-        slow_work_thread_processing[id] = NULL;
-        smp_mb();
-        if (slow_work_unreg_work_item == work ||
-            slow_work_unreg_module == module)
-                wake_up_all(&slow_work_unreg_wq);
-#endif
+        slow_work_done_thread_processing(id, work);
 
         return true;
 
@@ -310,7 +320,7 @@ auto_requeue:
         else
                 list_add_tail(&work->link, &slow_work_queue);
         spin_unlock_irq(&slow_work_queue_lock);
-        slow_work_thread_processing[id] = NULL;
+        slow_work_clear_thread_processing(id);
         return true;
 }
 
@@ -943,6 +953,7 @@ EXPORT_SYMBOL(slow_work_register_user);
  */
 static void slow_work_wait_for_items(struct module *module)
 {
+#ifdef CONFIG_MODULES
         DECLARE_WAITQUEUE(myself, current);
         struct slow_work *work;
         int loop;
@@ -989,6 +1000,7 @@ static void slow_work_wait_for_items(struct module *module)
 
         remove_wait_queue(&slow_work_unreg_wq, &myself);
         mutex_unlock(&slow_work_unreg_sync_lock);
+#endif /* CONFIG_MODULES */
 }
 
 /**