svn commit: r309670 - head/sys/dev/hyperv/vmbus

[Sepherosa Ziehau]

Author: sephe
Date: Wed Dec  7 08:12:02 2016
New Revision: 309670
URL: https://svnweb.freebsd.org/changeset/base/309670

Log:
  hyperv/vmbus: Use pause if possible.
  
  This makes booting on Hyper-V w/ small # of vCPUs work properly.
  
  Reported by:  Hongxiong Xian <v-hoxian microsoft com>, Hongjiang Zhang 
<honzhan microsoft com>
  MFC after:    1 week
  Sponsored by: Microsoft

Modified:
  head/sys/dev/hyperv/vmbus/vmbus_chan.c

Modified: head/sys/dev/hyperv/vmbus/vmbus_chan.c
==============================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_chan.c      Wed Dec  7 07:27:47 2016        
(r309669)
+++ head/sys/dev/hyperv/vmbus/vmbus_chan.c      Wed Dec  7 08:12:02 2016        
(r309670)
@@ -67,7 +67,7 @@ static void                   vmbus_chan_set_chmap(struc
 static void                    vmbus_chan_clear_chmap(struct vmbus_channel *);
 static void                    vmbus_chan_detach(struct vmbus_channel *);
 static bool                    vmbus_chan_wait_revoke(
-                                   const struct vmbus_channel *);
+                                   const struct vmbus_channel *, bool);
 
 static void                    vmbus_chan_ins_prilist(struct vmbus_softc *,
                                    struct vmbus_channel *);
@@ -478,14 +478,14 @@ vmbus_chan_open_br(struct vmbus_channel 
                                msg = vmbus_msghc_poll_result(sc, mh);
                                if (msg != NULL)
                                        break;
-                               DELAY(1000);
+                               pause("rchopen", 1);
                        }
 #undef REVOKE_LINGER
                        if (msg == NULL)
                                vmbus_msghc_exec_cancel(sc, mh);
                        break;
                }
-               DELAY(1000);
+               pause("chopen", 1);
        }
        if (msg != NULL) {
                status = ((const struct vmbus_chanmsg_chopen_resp *)
@@ -658,7 +658,7 @@ vmbus_chan_gpadl_connect(struct vmbus_ch
 }
 
 static bool
-vmbus_chan_wait_revoke(const struct vmbus_channel *chan)
+vmbus_chan_wait_revoke(const struct vmbus_channel *chan, bool can_sleep)
 {
 #define WAIT_COUNT     200     /* 200ms */
 
@@ -667,8 +667,10 @@ vmbus_chan_wait_revoke(const struct vmbu
        for (i = 0; i < WAIT_COUNT; ++i) {
                if (vmbus_chan_is_revoked(chan))
                        return (true);
-               /* Not sure about the context; use busy-wait. */
-               DELAY(1000);
+               if (can_sleep)
+                       pause("wchrev", 1);
+               else
+                       DELAY(1000);
        }
        return (false);
 
@@ -705,7 +707,7 @@ vmbus_chan_gpadl_disconnect(struct vmbus
        if (error) {
                vmbus_msghc_put(sc, mh);
 
-               if (vmbus_chan_wait_revoke(chan)) {
+               if (vmbus_chan_wait_revoke(chan, true)) {
                        /*
                         * Error is benign; this channel is revoked,
                         * so this GPADL will not be touched anymore.
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