Mention gdb+vkernel issues

diff --git a/docs/howtos/HowToDebugVKernels/index.mdwn b/docs/howtos/HowToDebugVKernels/index.mdwn
index 1617347..808518b 100644 (file)
--- a/docs/howtos/HowToDebugVKernels/index.mdwn
+++ b/docs/howtos/HowToDebugVKernels/index.mdwn
@@ -194,4 +194,12 @@ Oops. There is no trace to any vnode, whatsoever, for this process. The code wil
     #6  0x00000000 in ?? ()
     (gdb) 
 
-When the vkernel is sitting at a db> prompt all vkernel threads representing virtual cpu's except the one handling the db> prompt itself will be suspended in stopsig(). The backtrace only sees one of the N threads.
+When the vkernel is sitting at a db> prompt all vkernel threads representing virtual cpu's except the one handling the db> prompt itself 
+will be suspended in stopsig(). The backtrace only sees one of the N threads.
+
+## Gdb + vkernel issues
+gdb and vkernel (SMP or not) don't play well together anymore.  It is possible to get into
+a state where the vkernel is in state "stop" and the vkernel is in "wait", and nothing moves on.
+The only help is to kill gdb, which either makes the vkernel run again, or kills it as well.
+
+See also [this bug report](http://bugs.dragonflybsd.org/issue1301).