smp: don't warn about csd->flags having CSD_FLAG_LOCK cleared for !wait

blk-mq reuses the request potentially immediately, since the most
cache hot is always given out first. This means that rq->csd could
be reused between csd->func() being called and csd_unlock() being
called. This isn't a problem, since we never use wait == 1 for
the smp call function. Add CSD_FLAG_WAIT to be able to tell the
difference, retaining the warning for other cases.

Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
index 46d3d0b48a8d..dbc3d42d2c68 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -18,6 +18,7 @@
 #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
 enum {
         CSD_FLAG_LOCK           = 0x01,
+        CSD_FLAG_WAIT           = 0x02,
 };
 
 struct call_function_data {
@@ -124,7 +125,7 @@ static void csd_lock(struct call_single_data *csd)
 
 static void csd_unlock(struct call_single_data *csd)
 {
-        WARN_ON(!(csd->flags & CSD_FLAG_LOCK));
+        WARN_ON((csd->flags & CSD_FLAG_WAIT) && !(csd->flags & CSD_FLAG_LOCK));
 
         /*
          * ensure we're all done before releasing data:
@@ -146,6 +147,9 @@ void generic_exec_single(int cpu, struct call_single_data *csd, int wait)
         unsigned long flags;
         int ipi;
 
+        if (wait)
+                csd->flags |= CSD_FLAG_WAIT;
+
         raw_spin_lock_irqsave(&dst->lock, flags);
         ipi = list_empty(&dst->list);
         list_add_tail(&csd->list, &dst->list);