[Xen-devel] [PATCH] tools: blktap2 fix stack overflow when closing vbd with pending_requests

[weiwei li <weiweili821@xxxxxxxxx>]

From: Weiwei Li<nuonuoli@xxxxxxxxxxx>

When we close blktap and pending_requests have been completed yet, the 

callchain like this:

 

tapdisk_vbd_close-->with pending_requests

-->td_flag_set(vbd->state, TD_VBD_SHUTDOWN_REQUESTED);

-->tapdisk_vbd_kick

-->tapdisk_vbd_check_state

-->tapdisk_vbd_close

-->tapdisk_vbd_shutdown

-->tapdisk_vbd_kick

which will inter a deadloop as above and makes stack overflow.

To fix this, we just clear TD_VBD_SHUTDOWN_REQUESTED flag before

tapdisk_vbd_shutdown.

 

Signed-off-by: Weiwei Li<nuonuoli@xxxxxxxxxxx>

Signed-off-by: Xiaoming Gao <newtongao@xxxxxxxxxxx>

Signed-off-by: Yi Li <peteryili@xxxxxxxxxxx>

 

---

 tools/blktap2/drivers/tapdisk-vbd.c |    3 ++-

 1 files changed, 2 insertions(+), 1 deletions(-)

 

diff --git a/tools/blktap2/drivers/tapdisk-vbd.c b/tools/blktap2/drivers/tapdisk-vbd.c

index c665f27..a6f697d 100644

--- a/tools/blktap2/drivers/tapdisk-vbd.c

+++ b/tools/blktap2/drivers/tapdisk-vbd.c

@@ -795,6 +795,7 @@ tapdisk_vbd_close(td_vbd_t *vbd)

       !list_empty(&vbd->completed_requests)))

  goto fail;

 

+ td_flag_clear(vbd->state, TD_VBD_SHUTDOWN_REQUESTED);

  return tapdisk_vbd_shutdown(vbd);

 

 fail:

@@ -1100,7 +1101,7 @@ tapdisk_vbd_check_state(td_vbd_t *vbd)

  if (td_flag_test(vbd->state, TD_VBD_PAUSE_REQUESTED))

  tapdisk_vbd_pause(vbd);

 

- if (td_flag_test(vbd->state, TD_VBD_SHUTDOWN_REQUESTED))

+ if (td_flag_test(vbd->state, TD_VBD_SHUTDOWN_REQUESTED) && list_empty(&vbd->pending_requests))

  tapdisk_vbd_close(vbd);

 }

 

-- 

1.7.1

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