watchdog: implement error handling in update_watchdog_all_cpus() and callers

update_watchdog_all_cpus() now passes errors from watchdog_park_threads()
up to functions in the call chain.  This allows watchdog_enable_all_cpus()
and proc_watchdog_update() to handle such errors too.

Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 23 insertions, 7 deletions

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index f0f8a78512a5..704f93317666 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -731,10 +731,17 @@ void lockup_detector_resume(void)
         mutex_unlock(&watchdog_proc_mutex);
 }
 
-static void update_watchdog_all_cpus(void)
+static int update_watchdog_all_cpus(void)
 {
-        watchdog_park_threads();
+        int ret;
+
+        ret = watchdog_park_threads();
+        if (ret)
+                return ret;
+
         watchdog_unpark_threads();
+
+        return 0;
 }
 
 static int watchdog_enable_all_cpus(void)
@@ -753,9 +760,17 @@ static int watchdog_enable_all_cpus(void)
                  * Enable/disable the lockup detectors or
                  * change the sample period 'on the fly'.
                  */
-                update_watchdog_all_cpus();
+                err = update_watchdog_all_cpus();
+
+                if (err) {
+                        watchdog_disable_all_cpus();
+                        pr_err("Failed to update lockup detectors, disabled\n");
+                }
         }
 
+        if (err)
+                watchdog_enabled = 0;
+
         return err;
 }
 
@@ -851,12 +866,13 @@ static int proc_watchdog_common(int which, struct ctl_table *table, int write,
                 } while (cmpxchg(&watchdog_enabled, old, new) != old);
 
                 /*
-                 * Update the run state of the lockup detectors.
-                 * Restore 'watchdog_enabled' on failure.
+                 * Update the run state of the lockup detectors. There is _no_
+                 * need to check the value returned by proc_watchdog_update()
+                 * and to restore the previous value of 'watchdog_enabled' as
+                 * both lockup detectors are disabled if proc_watchdog_update()
+                 * returns an error.
                  */
                 err = proc_watchdog_update();
-                if (err)
-                        watchdog_enabled = old;
         }
 out:
         mutex_unlock(&watchdog_proc_mutex);