lockdep: suggest the fix for "lockdep bfs error:-1" on print_bfs_bug

When lockdep fails while performing the Breadth-first-search operation
due to lack of memory, hint that increasing the value of the config
switch LOCKDEP_CIRCULAR_QUEUE_BITS should fix the warning.

Preface the scary backtrace with the suggestion:

    [  163.849242] Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:
    [  163.849248] ------------[ cut here ]------------
    [  163.849250] lockdep bfs error:-1
    [  163.849263] WARNING: CPU: 24 PID: 2454 at kernel/locking/lockdep.c:2091 print_bfs_bug+0x27/0x40
    ...

Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Link: https://lkml.kernel.org/r/Zqkmy0lS-9Sw0M9j@uudg.org

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 726b22ce7d0b018d605655d40523a3bb41bcf0b6..fee21f3c3b9972095587b315cc191ebab8d9653e 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2067,6 +2067,9 @@ static noinline void print_bfs_bug(int ret)
        /*
         * Breadth-first-search failed, graph got corrupted?
         */
+       if (ret == BFS_EQUEUEFULL)
+               pr_warn("Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:\n");
+
        WARN(1, "lockdep bfs error:%d\n", ret);
 }