On 12/9/18 11:01 AM, Guenter Roeck wrote:
> On 12/9/18 9:50 AM, Jens Axboe wrote:
>> On 12/9/18 9:58 AM, Guenter Roeck wrote:
>>> On Sun, Dec 09, 2018 at 07:26:47AM -0700, Jens Axboe wrote:
>>>>
>>>> Ming that lockdep spews the following trace. What this essentially says
>>>> is that the sbitmap swap_lock was used inconsistently in IRQ enabled
>>>> and disabled context, and that is usually indicative of a bug that will
>>>> cause a deadlock.
>>>>
>>>> For this case, it's a false positive. The swap_lock is used from process
>>>> context only, when we swap the bits in the word and cleared mask. We
>>>> also end up doing that when we are getting a driver tag, from the
>>>> blk_mq_mark_tag_wait(), and from there we hold the waitqueue lock with
>>>> IRQs disabled. However, this isn't from an actual IRQ, it's still
>>>> process context.
>>>>
>>>> Mark the swap_lock as not needing validation to silence this warning.
>>>>
>>>
>>> checkpatch says:
>>>
>>> $ scripts/checkpatch.pl jens2
>>> ERROR: lockdep_no_validate class is reserved for device->mutex.
>>> #357: FILE: lib/sbitmap.c:68:
>>> + lockdep_set_novalidate_class(&sb->map[i].swap_lock);
>>>
>>> ... which I think explains the warning I am seeing with this patch applied.
>>
>> Try the other patch I sent out earlier, that should work.
>>
>
> Ok, I am lost. No idea which patch you refer to. I'll just wait for the problem
> to disappear from -next, or report it again if it shows up in mainline.
This one, sent out this morning in this thread:
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index a89fbe7cf6ca..23da156f7a17 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -118,8 +118,13 @@ static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
{
unsigned long mask, val;
+ unsigned long flags;
bool ret = false;
+ /* Silence bogus lockdep warning */
+#if defined(CONFIG_LOCKDEP)
+ local_irq_save(flags);
+#endif
spin_lock(&sb->map[index].swap_lock);
if (!sb->map[index].cleared)
@@ -142,6 +147,9 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index)
ret = true;
out_unlock:
spin_unlock(&sb->map[index].swap_lock);
+#if defined(CONFIG_LOCKDEP)
+ local_irq_restore(flags);
+#endif
return ret;
}
--
Jens Axboe
