From 557c88c3ac835f343b6510f5b6ed309773042c87 Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Wed, 5 Apr 2017 17:20:18 -0700
Subject: [PATCH] Change pollset rules

---
 src/core/lib/iomgr/ev_epoll_linux.c     | 4 ++--
 src/core/lib/iomgr/ev_poll_posix.c      | 4 ++--
 src/core/lib/iomgr/pollset.h            | 4 ++++
 src/core/lib/iomgr/pollset_windows.c    | 4 ++--
 src/core/lib/surface/completion_queue.c | 5 ++---
 5 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/src/core/lib/iomgr/ev_epoll_linux.c b/src/core/lib/iomgr/ev_epoll_linux.c
index 7014b983495..e5cf54f10a9 100644
--- a/src/core/lib/iomgr/ev_epoll_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_linux.c
@@ -1717,7 +1717,7 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
   worker.pt_id = pthread_self();
   gpr_atm_no_barrier_store(&worker.is_kicked, (gpr_atm)0);
 
-  *worker_hdl = &worker;
+  if (worker_hdl) *worker_hdl = &worker;
 
   gpr_tls_set(&g_current_thread_pollset, (intptr_t)pollset);
   gpr_tls_set(&g_current_thread_worker, (intptr_t)&worker);
@@ -1795,7 +1795,7 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
     gpr_mu_lock(&pollset->po.mu);
   }
 
-  *worker_hdl = NULL;
+  if (worker_hdl) *worker_hdl = NULL;
 
   gpr_tls_set(&g_current_thread_pollset, (intptr_t)0);
   gpr_tls_set(&g_current_thread_worker, (intptr_t)0);
diff --git a/src/core/lib/iomgr/ev_poll_posix.c b/src/core/lib/iomgr/ev_poll_posix.c
index d90f2233622..9834cdd1979 100644
--- a/src/core/lib/iomgr/ev_poll_posix.c
+++ b/src/core/lib/iomgr/ev_poll_posix.c
@@ -871,7 +871,7 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                                 grpc_pollset_worker **worker_hdl,
                                 gpr_timespec now, gpr_timespec deadline) {
   grpc_pollset_worker worker;
-  *worker_hdl = &worker;
+  if (worker_hdl) *worker_hdl = &worker;
   grpc_error *error = GRPC_ERROR_NONE;
 
   /* Avoid malloc for small number of elements. */
@@ -1092,7 +1092,7 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
       gpr_mu_lock(&pollset->mu);
     }
   }
-  *worker_hdl = NULL;
+  if (worker_hdl) *worker_hdl = NULL;
   GPR_TIMER_END("pollset_work", 0);
   GRPC_LOG_IF_ERROR("pollset_work", GRPC_ERROR_REF(error));
   return error;
diff --git a/src/core/lib/iomgr/pollset.h b/src/core/lib/iomgr/pollset.h
index e19ce697b8d..9bf3cdac89e 100644
--- a/src/core/lib/iomgr/pollset.h
+++ b/src/core/lib/iomgr/pollset.h
@@ -75,6 +75,10 @@ void grpc_pollset_destroy(grpc_pollset *pollset);
    and it is guaranteed that it will not be released by grpc_pollset_work
    AFTER worker has been destroyed.
 
+   It's legal for worker to be NULL: in that case, this specific thread can not
+   be directly woken with a kick, but maybe be indirectly (with a kick against
+   the pollset as a whole).
+
    Tries not to block past deadline.
    May call grpc_closure_list_run on grpc_closure_list, without holding the
    pollset
diff --git a/src/core/lib/iomgr/pollset_windows.c b/src/core/lib/iomgr/pollset_windows.c
index 17043c1ea1a..04c6b717475 100644
--- a/src/core/lib/iomgr/pollset_windows.c
+++ b/src/core/lib/iomgr/pollset_windows.c
@@ -120,7 +120,7 @@ grpc_error *grpc_pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                               grpc_pollset_worker **worker_hdl,
                               gpr_timespec now, gpr_timespec deadline) {
   grpc_pollset_worker worker;
-  *worker_hdl = &worker;
+  if (worker_hdl) *worker_hdl = &worker;
 
   int added_worker = 0;
   worker.links[GRPC_POLLSET_WORKER_LINK_POLLSET].next =
@@ -185,7 +185,7 @@ done:
     remove_worker(&worker, GRPC_POLLSET_WORKER_LINK_POLLSET);
   }
   gpr_cv_destroy(&worker.cv);
-  *worker_hdl = NULL;
+  if (worker_hdl) *worker_hdl = NULL;
   return GRPC_ERROR_NONE;
 }
 
diff --git a/src/core/lib/surface/completion_queue.c b/src/core/lib/surface/completion_queue.c
index b4594817e45..3273addf1d0 100644
--- a/src/core/lib/surface/completion_queue.c
+++ b/src/core/lib/surface/completion_queue.c
@@ -345,7 +345,6 @@ static void dump_pending_tags(grpc_completion_queue *cc) {}
 grpc_event grpc_completion_queue_next(grpc_completion_queue *cc,
                                       gpr_timespec deadline, void *reserved) {
   grpc_event ret;
-  grpc_pollset_worker *worker = NULL;
   gpr_timespec now;
 
   GPR_TIMER_BEGIN("grpc_completion_queue_next", 0);
@@ -426,8 +425,8 @@ grpc_event grpc_completion_queue_next(grpc_completion_queue *cc,
       gpr_mu_lock(cc->mu);
       continue;
     } else {
-      grpc_error *err = grpc_pollset_work(&exec_ctx, POLLSET_FROM_CQ(cc),
-                                          &worker, now, iteration_deadline);
+      grpc_error *err = grpc_pollset_work(&exec_ctx, POLLSET_FROM_CQ(cc), NULL,
+                                          now, iteration_deadline);
       if (err != GRPC_ERROR_NONE) {
         gpr_mu_unlock(cc->mu);
         const char *msg = grpc_error_string(err);