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>

diff --git a/kernel/smp.c b/kernel/smp.c
index 46d3d0b48a8d22298256c3ba94d374148f8cd6ed..dbc3d42d2c686c98d85d83c7890bc59a1cc5bae4 100644 (file)
--- 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);