13902 Fix for 13717 may break 8-disk raidz2
13915 installctx() blocking allocate causes problems
Portions contributed by: Jerry Jelinek <gjelinek@gmail.com>
Change-Id: I934d69946cec42630fc541fa8c7385b862b69ca2

*** 19,28 ****
--- 19,29 ----
   * CDDL HEADER END
   */
  
  /*
   * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
+  * Copyright 2021 Joyent, Inc.
   */
  
  #include <sys/param.h>
  #include <sys/thread.h>
  #include <sys/cpuvar.h>
*** 316,326 ****
  
          /*
           * Add a device context to the subject thread.
           */
          installctx(t, ctx, kcpc_save, kcpc_restore, NULL,
!             kcpc_lwp_create, NULL, kcpc_free);
  
          /*
           * Ask the backend to program the hardware.
           */
          if (t == curthread) {
--- 317,327 ----
  
          /*
           * Add a device context to the subject thread.
           */
          installctx(t, ctx, kcpc_save, kcpc_restore, NULL,
!             kcpc_lwp_create, NULL, kcpc_free, NULL);
  
          /*
           * Ask the backend to program the hardware.
           */
          if (t == curthread) {
*** 1422,1432 ****
                  ttolwp(ct)->lwp_pcb.pcb_flags |= CPC_OVERFLOW;
                  aston(ct);
          }
  
          installctx(ct, cctx, kcpc_save, kcpc_restore,
!             NULL, kcpc_lwp_create, NULL, kcpc_free);
  }
  
  /*
   * Counter Stoppage Theory
   *
--- 1423,1433 ----
                  ttolwp(ct)->lwp_pcb.pcb_flags |= CPC_OVERFLOW;
                  aston(ct);
          }
  
          installctx(ct, cctx, kcpc_save, kcpc_restore,
!             NULL, kcpc_lwp_create, NULL, kcpc_free, NULL);
  }
  
  /*
   * Counter Stoppage Theory
   *