BackoffThrottle: wait() if past max

Otherwise, we risk spinning on wait_for() with a small
delay.

Fixes: http://tracker.ceph.com/issues/15953
Signed-off-by: Samuel Just <sjust@redhat.com>
(cherry picked from commit 6f835726a7df5b29a96849fc1362186fd2116d9b)

diff --git a/src/common/Throttle.cc b/src/common/Throttle.cc
index 14cf1ba894d91ee2d0d0d48361ea1c86cc4fc62f..8a52906cd5e5de436ac1470eb80e4f877be4c248 100644 (file)
--- a/src/common/Throttle.cc
+++ b/src/common/Throttle.cc
@@ -376,10 +376,15 @@ std::chrono::duration<double> BackoffThrottle::get(uint64_t c)
 
   auto start = std::chrono::system_clock::now();
   delay = _get_delay(c);
-  while ((delay > std::chrono::duration<double>(0)) ||
-        !((max == 0) || (current == 0) || ((current + c) <= max))) {
+  while (true) {
+    if (!((max == 0) || (current == 0) || (current + c) <= max)) {
+      (*ticket)->wait(l);
+    } else if (delay > std::chrono::duration<double>(0)) {
+      (*ticket)->wait_for(l, delay);
+    } else {
+      break;
+    }
     assert(ticket == waiters.begin());
-    (*ticket)->wait_for(l, delay);
     delay = _get_delay(c) - (std::chrono::system_clock::now() - start);
   }
   waiters.pop_front();