[Xen-devel] [PATCH 3/3] xen/blkback: don't use xen_blkif_get() in xen-blkback kthread

[Juergen Gross <jgross@xxxxxxxx>]

There is no need to use xen_blkif_get()/xen_blkif_put() in the kthread
of xen-blkback. Thread stopping is synchronous and using the blkif
reference counting in the kthread will avoid to ever let the reference
count drop to zero at the end of an I/O running concurrent to
disconnecting and multiple rings.

Setting ring->xenblkd to NULL after stopping the kthread isn't needed
as the kthread does this already.

Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Glenn Enright <glenn@xxxxxxxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 drivers/block/xen-blkback/blkback.c | 3 ---
 drivers/block/xen-blkback/xenbus.c  | 1 -
 2 files changed, 4 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index 726c32e35db9..6b14c509f3c7 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -609,8 +609,6 @@ int xen_blkif_schedule(void *arg)
        unsigned long timeout;
        int ret;
 
-       xen_blkif_get(blkif);
-
        set_freezable();
        while (!kthread_should_stop()) {
                if (try_to_freeze())
@@ -665,7 +663,6 @@ int xen_blkif_schedule(void *arg)
                print_stats(ring);
 
        ring->xenblkd = NULL;
-       xen_blkif_put(blkif);
 
        return 0;
 }
diff --git a/drivers/block/xen-blkback/xenbus.c 
b/drivers/block/xen-blkback/xenbus.c
index 4d2f57fa35da..1dc0ff5ed912 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -255,7 +255,6 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
                if (ring->xenblkd) {
                        kthread_stop(ring->xenblkd);
                        wake_up(&ring->shutdown_wq);
-                       ring->xenblkd = NULL;
                }
 
                /* The above kthread_stop() guarantees that at this point we
-- 
2.12.0


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