svn commit: r334145 - head/sys/dev/xen/blkback

[Roger Pau Monné]

Author: royger
Date: Thu May 24 10:19:54 2018
New Revision: 334145
URL: https://svnweb.freebsd.org/changeset/base/334145

Log:
  xen-blkback: don't unbind the interrupt while holding the lock
  
  There's no need to perform the interrupt unbind while holding the
  blkback lock, and doing so leads to the following LOR:
  
  lock order reversal: (sleepable after non-sleepable)
   1st 0xfffff8000802fe90 xbbd1 (xbbd1) @ /usr/src/sys/dev/xen/blkback/blkback.c:3423
   2nd 0xffffffff81fdf890 intrsrc (intrsrc) @ /usr/src/sys/x86/x86/intr_machdep.c:224
  stack backtrace:
  #0 0xffffffff80bdd993 at witness_debugger+0x73
  #1 0xffffffff80bdd814 at witness_checkorder+0xe34
  #2 0xffffffff80b7d798 at _sx_xlock+0x68
  #3 0xffffffff811b3913 at intr_remove_handler+0x43
  #4 0xffffffff811c63ef at xen_intr_unbind+0x10f
  #5 0xffffffff80a12ecf at xbb_disconnect+0x2f
  #6 0xffffffff80a12e54 at xbb_shutdown+0x1e4
  #7 0xffffffff80a10be4 at xbb_frontend_changed+0x54
  #8 0xffffffff80ed66a4 at xenbusb_back_otherend_changed+0x14
  #9 0xffffffff80a2a382 at xenwatch_thread+0x182
  #10 0xffffffff80b34164 at fork_exit+0x84
  #11 0xffffffff8101ec9e at fork_trampoline+0xe
  
  Reported by:    Nathan Friess <nathan.friess at gmail.com>
  Sponsored by:   Citrix Systems R&D

Modified:
  head/sys/dev/xen/blkback/blkback.c

Modified: head/sys/dev/xen/blkback/blkback.c
==============================================================================
--- head/sys/dev/xen/blkback/blkback.c	Thu May 24 10:18:31 2018	(r334144)
+++ head/sys/dev/xen/blkback/blkback.c	Thu May 24 10:19:54 2018	(r334145)
@@ -2803,9 +2803,8 @@ xbb_disconnect(struct xbb_softc *xbb)
 	if ((xbb->flags & XBBF_RING_CONNECTED) == 0)
 		return (0);
 
-	xen_intr_unbind(&xbb->xen_intr_handle);
-
 	mtx_unlock(&xbb->lock);
+	xen_intr_unbind(&xbb->xen_intr_handle);
 	taskqueue_drain(xbb->io_taskqueue, &xbb->io_task); 
 	mtx_lock(&xbb->lock);