Merge pull request #8797 from sreecha/pss_pi

Rewrite pollset_set implementation

1 files changed, 272 insertions, 313 deletions

diff --git a/src/core/lib/iomgr/ev_epoll_linux.c b/src/core/lib/iomgr/ev_epoll_linux.c
index 07fbfd849e..1b15e0eb4f 100644
--- a/src/core/lib/iomgr/ev_epoll_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_linux.c
@@ -69,6 +69,9 @@ static int grpc_polling_trace = 0; /* Disabled by default */
     gpr_log(GPR_INFO, (fmt), __VA_ARGS__); \
   }
 
+/* Uncomment the following enable extra checks on poll_object operations */
+/* #define PO_DEBUG */
+
 static int grpc_wakeup_signal = -1;
 static bool is_grpc_wakeup_signal_initialized = false;
 
@@ -95,10 +98,42 @@ void grpc_use_signal(int signum) {
 
 struct polling_island;
 
+typedef enum {
+  POLL_OBJ_FD,
+  POLL_OBJ_POLLSET,
+  POLL_OBJ_POLLSET_SET
+} poll_obj_type;
+
+typedef struct poll_obj {
+#ifdef PO_DEBUG
+  poll_obj_type obj_type;
+#endif
+  gpr_mu mu;
+  struct polling_island *pi;
+} poll_obj;
+
+const char *poll_obj_string(poll_obj_type po_type) {
+  switch (po_type) {
+    case POLL_OBJ_FD:
+      return "fd";
+    case POLL_OBJ_POLLSET:
+      return "pollset";
+    case POLL_OBJ_POLLSET_SET:
+      return "pollset_set";
+  }
+
+  GPR_UNREACHABLE_CODE(return "UNKNOWN");
+}
+
 /*******************************************************************************
  * Fd Declarations
  */
+
+#define FD_FROM_PO(po) ((grpc_fd *)(po))
+
 struct grpc_fd {
+  poll_obj po;
+
   int fd;
   /* refst format:
        bit 0    : 1=Active / 0=Orphaned
@@ -106,8 +141,6 @@ struct grpc_fd {
      Ref/Unref by two to avoid altering the orphaned bit */
   gpr_atm refst;
 
-  gpr_mu mu;
-
   /* Indicates that the fd is shutdown and that any pending read/write closures
      should fail */
   bool shutdown;
@@ -120,9 +153,6 @@ struct grpc_fd {
   grpc_closure *read_closure;
   grpc_closure *write_closure;
 
-  /* The polling island to which this fd belongs to (protected by mu) */
-  struct polling_island *polling_island;
-
   struct grpc_fd *freelist_next;
   grpc_closure *on_done_closure;
 
@@ -225,41 +255,21 @@ struct grpc_pollset_worker {
 };
 
 struct grpc_pollset {
-  gpr_mu mu;
+  poll_obj po;
+
   grpc_pollset_worker root_worker;
   bool kicked_without_pollers;
 
   bool shutting_down;          /* Is the pollset shutting down ? */
   bool finish_shutdown_called; /* Is the 'finish_shutdown_locked()' called ? */
   grpc_closure *shutdown_done; /* Called after after shutdown is complete */
-
-  /* The polling island to which this pollset belongs to */
-  struct polling_island *polling_island;
 };
 
 /*******************************************************************************
  * Pollset-set Declarations
  */
-/* TODO: sreek - Change the pollset_set implementation such that a pollset_set
- * directly points to a polling_island (and adding an fd/pollset/pollset_set to
- * the current pollset_set would result in polling island merges. This would
- * remove the need to maintain fd_count here. This will also significantly
- * simplify the grpc_fd structure since we would no longer need to explicitly
- * maintain the orphaned state */
 struct grpc_pollset_set {
-  gpr_mu mu;
-
-  size_t pollset_count;
-  size_t pollset_capacity;
-  grpc_pollset **pollsets;
-
-  size_t pollset_set_count;
-  size_t pollset_set_capacity;
-  struct grpc_pollset_set **pollset_sets;
-
-  size_t fd_count;
-  size_t fd_capacity;
-  grpc_fd **fds;
+  poll_obj po;
 };
 
 /*******************************************************************************
@@ -915,7 +925,7 @@ static void fd_global_shutdown(void) {
   while (fd_freelist != NULL) {
     grpc_fd *fd = fd_freelist;
     fd_freelist = fd_freelist->freelist_next;
-    gpr_mu_destroy(&fd->mu);
+    gpr_mu_destroy(&fd->po.mu);
     gpr_free(fd);
   }
   gpr_mu_destroy(&fd_freelist_mu);
@@ -933,13 +943,17 @@ static grpc_fd *fd_create(int fd, const char *name) {
 
   if (new_fd == NULL) {
     new_fd = gpr_malloc(sizeof(grpc_fd));
-    gpr_mu_init(&new_fd->mu);
+    gpr_mu_init(&new_fd->po.mu);
   }
 
-  /* Note: It is not really needed to get the new_fd->mu lock here. If this is a
-     newly created fd (or an fd we got from the freelist), no one else would be
-     holding a lock to it anyway. */
-  gpr_mu_lock(&new_fd->mu);
+  /* Note: It is not really needed to get the new_fd->po.mu lock here. If this
+   * is a newly created fd (or an fd we got from the freelist), no one else
+   * would be holding a lock to it anyway. */
+  gpr_mu_lock(&new_fd->po.mu);
+  new_fd->po.pi = NULL;
+#ifdef PO_DEBUG
+  new_fd->po.obj_type = POLL_OBJ_FD;
+#endif
 
   gpr_atm_rel_store(&new_fd->refst, (gpr_atm)1);
   new_fd->fd = fd;
@@ -947,12 +961,11 @@ static grpc_fd *fd_create(int fd, const char *name) {
   new_fd->orphaned = false;
   new_fd->read_closure = CLOSURE_NOT_READY;
   new_fd->write_closure = CLOSURE_NOT_READY;
-  new_fd->polling_island = NULL;
   new_fd->freelist_next = NULL;
   new_fd->on_done_closure = NULL;
   new_fd->read_notifier_pollset = NULL;
 
-  gpr_mu_unlock(&new_fd->mu);
+  gpr_mu_unlock(&new_fd->po.mu);
 
   char *fd_name;
   gpr_asprintf(&fd_name, "%s fd=%d", name, fd);
@@ -964,17 +977,13 @@ static grpc_fd *fd_create(int fd, const char *name) {
   return new_fd;
 }
 
-static bool fd_is_orphaned(grpc_fd *fd) {
-  return (gpr_atm_acq_load(&fd->refst) & 1) == 0;
-}
-
 static int fd_wrapped_fd(grpc_fd *fd) {
   int ret_fd = -1;
-  gpr_mu_lock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
   if (!fd->orphaned) {
     ret_fd = fd->fd;
   }
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
 
   return ret_fd;
 }
@@ -986,7 +995,7 @@ static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
   grpc_error *error = GRPC_ERROR_NONE;
   polling_island *unref_pi = NULL;
 
-  gpr_mu_lock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
   fd->on_done_closure = on_done;
 
   /* If release_fd is not NULL, we should be relinquishing control of the file
@@ -1006,25 +1015,25 @@ static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
 
   /* Remove the fd from the polling island:
      - Get a lock on the latest polling island (i.e the last island in the
-       linked list pointed by fd->polling_island). This is the island that
+       linked list pointed by fd->po.pi). This is the island that
        would actually contain the fd
      - Remove the fd from the latest polling island
      - Unlock the latest polling island
-     - Set fd->polling_island to NULL (but remove the ref on the polling island
+     - Set fd->po.pi to NULL (but remove the ref on the polling island
        before doing this.) */
-  if (fd->polling_island != NULL) {
-    polling_island *pi_latest = polling_island_lock(fd->polling_island);
+  if (fd->po.pi != NULL) {
+    polling_island *pi_latest = polling_island_lock(fd->po.pi);
     polling_island_remove_fd_locked(pi_latest, fd, is_fd_closed, &error);
     gpr_mu_unlock(&pi_latest->mu);
 
-    unref_pi = fd->polling_island;
-    fd->polling_island = NULL;
+    unref_pi = fd->po.pi;
+    fd->po.pi = NULL;
   }
 
   grpc_exec_ctx_sched(exec_ctx, fd->on_done_closure, GRPC_ERROR_REF(error),
                       NULL);
 
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
   UNREF_BY(fd, 2, reason); /* Drop the reference */
   if (unref_pi != NULL) {
     /* Unref stale polling island here, outside the fd lock above.
@@ -1089,23 +1098,23 @@ static grpc_pollset *fd_get_read_notifier_pollset(grpc_exec_ctx *exec_ctx,
                                                   grpc_fd *fd) {
   grpc_pollset *notifier = NULL;
 
-  gpr_mu_lock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
   notifier = fd->read_notifier_pollset;
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
 
   return notifier;
 }
 
 static bool fd_is_shutdown(grpc_fd *fd) {
-  gpr_mu_lock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
   const bool r = fd->shutdown;
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
   return r;
 }
 
 /* Might be called multiple times */
 static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  gpr_mu_lock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
   /* Do the actual shutdown only once */
   if (!fd->shutdown) {
     fd->shutdown = true;
@@ -1116,28 +1125,28 @@ static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
     set_ready_locked(exec_ctx, fd, &fd->read_closure);
     set_ready_locked(exec_ctx, fd, &fd->write_closure);
   }
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
 }
 
 static void fd_notify_on_read(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                               grpc_closure *closure) {
-  gpr_mu_lock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
   notify_on_locked(exec_ctx, fd, &fd->read_closure, closure);
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
 }
 
 static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                                grpc_closure *closure) {
-  gpr_mu_lock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
   notify_on_locked(exec_ctx, fd, &fd->write_closure, closure);
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
 }
 
 static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) {
-  gpr_mu_lock(&fd->mu);
-  grpc_workqueue *workqueue = GRPC_WORKQUEUE_REF(
-      (grpc_workqueue *)fd->polling_island, "fd_get_workqueue");
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
+  grpc_workqueue *workqueue =
+      GRPC_WORKQUEUE_REF((grpc_workqueue *)fd->po.pi, "fd_get_workqueue");
+  gpr_mu_unlock(&fd->po.mu);
   return workqueue;
 }
 
@@ -1277,8 +1286,12 @@ static grpc_error *kick_poller(void) {
 }
 
 static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
-  gpr_mu_init(&pollset->mu);
-  *mu = &pollset->mu;
+  gpr_mu_init(&pollset->po.mu);
+  *mu = &pollset->po.mu;
+  pollset->po.pi = NULL;
+#ifdef PO_DEBUG
+  pollset->po.obj_type = POLL_OBJ_POLLSET;
+#endif
 
   pollset->root_worker.next = pollset->root_worker.prev = &pollset->root_worker;
   pollset->kicked_without_pollers = false;
@@ -1286,8 +1299,6 @@ static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
   pollset->shutting_down = false;
   pollset->finish_shutdown_called = false;
   pollset->shutdown_done = NULL;
-
-  pollset->polling_island = NULL;
 }
 
 /* Convert a timespec to milliseconds:
@@ -1317,26 +1328,26 @@ static int poll_deadline_to_millis_timeout(gpr_timespec deadline,
 
 static void fd_become_readable(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                                grpc_pollset *notifier) {
-  /* Need the fd->mu since we might be racing with fd_notify_on_read */
-  gpr_mu_lock(&fd->mu);
+  /* Need the fd->po.mu since we might be racing with fd_notify_on_read */
+  gpr_mu_lock(&fd->po.mu);
   set_ready_locked(exec_ctx, fd, &fd->read_closure);
   fd->read_notifier_pollset = notifier;
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
 }
 
 static void fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  /* Need the fd->mu since we might be racing with fd_notify_on_write */
-  gpr_mu_lock(&fd->mu);
+  /* Need the fd->po.mu since we might be racing with fd_notify_on_write */
+  gpr_mu_lock(&fd->po.mu);
   set_ready_locked(exec_ctx, fd, &fd->write_closure);
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_unlock(&fd->po.mu);
 }
 
 static void pollset_release_polling_island(grpc_exec_ctx *exec_ctx,
                                            grpc_pollset *ps, char *reason) {
-  if (ps->polling_island != NULL) {
-    PI_UNREF(exec_ctx, ps->polling_island, reason);
+  if (ps->po.pi != NULL) {
+    PI_UNREF(exec_ctx, ps->po.pi, reason);
   }
-  ps->polling_island = NULL;
+  ps->po.pi = NULL;
 }
 
 static void finish_shutdown_locked(grpc_exec_ctx *exec_ctx,
@@ -1346,12 +1357,12 @@ static void finish_shutdown_locked(grpc_exec_ctx *exec_ctx,
 
   pollset->finish_shutdown_called = true;
 
-  /* Release the ref and set pollset->polling_island to NULL */
+  /* Release the ref and set pollset->po.pi to NULL */
   pollset_release_polling_island(exec_ctx, pollset, "ps_shutdown");
   grpc_exec_ctx_sched(exec_ctx, pollset->shutdown_done, GRPC_ERROR_NONE, NULL);
 }
 
-/* pollset->mu lock must be held by the caller before calling this */
+/* pollset->po.mu lock must be held by the caller before calling this */
 static void pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                              grpc_closure *closure) {
   GPR_TIMER_BEGIN("pollset_shutdown", 0);
@@ -1376,7 +1387,7 @@ static void pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
  * here */
 static void pollset_destroy(grpc_pollset *pollset) {
   GPR_ASSERT(!pollset_has_workers(pollset));
-  gpr_mu_destroy(&pollset->mu);
+  gpr_mu_destroy(&pollset->po.mu);
 }
 
 static void pollset_reset(grpc_pollset *pollset) {
@@ -1386,7 +1397,7 @@ static void pollset_reset(grpc_pollset *pollset) {
   pollset->finish_shutdown_called = false;
   pollset->kicked_without_pollers = false;
   pollset->shutdown_done = NULL;
-  GPR_ASSERT(pollset->polling_island == NULL);
+  GPR_ASSERT(pollset->po.pi == NULL);
 }
 
 static bool maybe_do_workqueue_work(grpc_exec_ctx *exec_ctx,
@@ -1426,7 +1437,7 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
   GPR_TIMER_BEGIN("pollset_work_and_unlock", 0);
 
   /* We need to get the epoll_fd to wait on. The epoll_fd is in inside the
-     latest polling island pointed by pollset->polling_island.
+     latest polling island pointed by pollset->po.pi
 
      Since epoll_fd is immutable, we can read it without obtaining the polling
      island lock. There is however a possibility that the polling island (from
@@ -1435,36 +1446,36 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
      right-away from epoll_wait() and pick up the latest polling_island the next
      this function (i.e pollset_work_and_unlock()) is called */
 
-  if (pollset->polling_island == NULL) {
-    pollset->polling_island = polling_island_create(exec_ctx, NULL, error);
-    if (pollset->polling_island == NULL) {
+  if (pollset->po.pi == NULL) {
+    pollset->po.pi = polling_island_create(exec_ctx, NULL, error);
+    if (pollset->po.pi == NULL) {
       GPR_TIMER_END("pollset_work_and_unlock", 0);
       return; /* Fatal error. We cannot continue */
     }
 
-    PI_ADD_REF(pollset->polling_island, "ps");
+    PI_ADD_REF(pollset->po.pi, "ps");
     GRPC_POLLING_TRACE("pollset_work: pollset: %p created new pi: %p",
-                       (void *)pollset, (void *)pollset->polling_island);
+                       (void *)pollset, (void *)pollset->po.pi);
   }
 
-  pi = polling_island_maybe_get_latest(pollset->polling_island);
+  pi = polling_island_maybe_get_latest(pollset->po.pi);
   epoll_fd = pi->epoll_fd;
 
-  /* Update the pollset->polling_island since the island being pointed by
-     pollset->polling_island maybe older than the one pointed by pi) */
-  if (pollset->polling_island != pi) {
+  /* Update the pollset->po.pi since the island being pointed by
+     pollset->po.pi maybe older than the one pointed by pi) */
+  if (pollset->po.pi != pi) {
     /* Always do PI_ADD_REF before PI_UNREF because PI_UNREF may cause the
        polling island to be deleted */
     PI_ADD_REF(pi, "ps");
-    PI_UNREF(exec_ctx, pollset->polling_island, "ps");
-    pollset->polling_island = pi;
+    PI_UNREF(exec_ctx, pollset->po.pi, "ps");
+    pollset->po.pi = pi;
   }
 
   /* Add an extra ref so that the island does not get destroyed (which means
      the epoll_fd won't be closed) while we are are doing an epoll_wait() on the
      epoll_fd */
   PI_ADD_REF(pi, "ps_work");
-  gpr_mu_unlock(&pollset->mu);
+  gpr_mu_unlock(&pollset->po.mu);
 
   /* If we get some workqueue work to do, it might end up completing an item on
      the completion queue, so there's no need to poll... so we skip that and
@@ -1537,17 +1548,17 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
   GPR_ASSERT(pi != NULL);
 
   /* Before leaving, release the extra ref we added to the polling island. It
-     is important to use "pi" here (i.e our old copy of pollset->polling_island
+     is important to use "pi" here (i.e our old copy of pollset->po.pi
      that we got before releasing the polling island lock). This is because
-     pollset->polling_island pointer might get udpated in other parts of the
+     pollset->po.pi pointer might get udpated in other parts of the
      code when there is an island merge while we are doing epoll_wait() above */
   PI_UNREF(exec_ctx, pi, "ps_work");
 
   GPR_TIMER_END("pollset_work_and_unlock", 0);
 }
 
-/* pollset->mu lock must be held by the caller before calling this.
-   The function pollset_work() may temporarily release the lock (pollset->mu)
+/* pollset->po.mu lock must be held by the caller before calling this.
+   The function pollset_work() may temporarily release the lock (pollset->po.mu)
    during the course of its execution but it will always re-acquire the lock and
    ensure that it is held by the time the function returns */
 static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
@@ -1617,7 +1628,7 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                             &g_orig_sigmask, &error);
     grpc_exec_ctx_flush(exec_ctx);
 
-    gpr_mu_lock(&pollset->mu);
+    gpr_mu_lock(&pollset->po.mu);
 
     /* Note: There is no need to reset worker.is_kicked to 0 since we are no
        longer going to use this worker */
@@ -1637,9 +1648,9 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
     GPR_TIMER_MARK("pollset_work.finish_shutdown_locked", 0);
     finish_shutdown_locked(exec_ctx, pollset);
 
-    gpr_mu_unlock(&pollset->mu);
+    gpr_mu_unlock(&pollset->po.mu);
     grpc_exec_ctx_flush(exec_ctx);
-    gpr_mu_lock(&pollset->mu);
+    gpr_mu_lock(&pollset->po.mu);
   }
 
   *worker_hdl = NULL;
@@ -1653,130 +1664,160 @@ static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
   return error;
 }
 
-static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                           grpc_fd *fd) {
-  GPR_TIMER_BEGIN("pollset_add_fd", 0);
-
-  grpc_error *error = GRPC_ERROR_NONE;
+static void add_poll_object(grpc_exec_ctx *exec_ctx, poll_obj *bag,
+                            poll_obj_type bag_type, poll_obj *item,
+                            poll_obj_type item_type) {
+  GPR_TIMER_BEGIN("add_poll_object", 0);
 
-  gpr_mu_lock(&pollset->mu);
-  gpr_mu_lock(&fd->mu);
+#ifdef PO_DEBUG
+  GPR_ASSERT(item->obj_type == item_type);
+  GPR_ASSERT(bag->obj_type == bag_type);
+#endif
 
+  grpc_error *error = GRPC_ERROR_NONE;
   polling_island *pi_new = NULL;
 
+  gpr_mu_lock(&bag->mu);
+  gpr_mu_lock(&item->mu);
+
 retry:
-  /* 1) If fd->polling_island and pollset->polling_island are both non-NULL and
-   *    equal, do nothing.
-   * 2) If fd->polling_island and pollset->polling_island are both NULL, create
-   *    a new polling island (with a refcount of 2) and make the polling_island
-   *    fields in both fd and pollset to point to the new island
-   * 3) If one of fd->polling_island or pollset->polling_island is NULL, update
-   *    the NULL polling_island field to point to the non-NULL polling_island
-   *    field (ensure that the refcount on the polling island is incremented by
-   *    1 to account for the newly added reference)
-   * 4) Finally, if fd->polling_island and pollset->polling_island are non-NULL
-   *    and different, merge both the polling islands and update the
-   *    polling_island fields in both fd and pollset to point to the merged
-   *    polling island.
+  /*
+   * 1) If item->pi and bag->pi are both non-NULL and equal, do nothing
+   * 2) If item->pi and bag->pi are both NULL, create a new polling island (with
+   *    a refcount of 2) and point item->pi and bag->pi to the new island
+   * 3) If exactly one of item->pi or bag->pi is NULL, update it to point to
+   *    the other's non-NULL pi
+   * 4) Finally if item->pi and bag-pi are non-NULL and not-equal, merge the
+   *    polling islands and update item->pi and bag->pi to point to the new
+   *    island
    */
 
-  if (fd->orphaned) {
-    gpr_mu_unlock(&fd->mu);
-    gpr_mu_unlock(&pollset->mu);
-    /* early out */
+  /* Early out if we are trying to add an 'fd' to a 'bag' but the fd is already
+   * orphaned */
+  if (item_type == POLL_OBJ_FD && (FD_FROM_PO(item))->orphaned) {
+    gpr_mu_unlock(&item->mu);
+    gpr_mu_unlock(&bag->mu);
     return;
   }
 
-  if (fd->polling_island == pollset->polling_island) {
-    pi_new = fd->polling_island;
+  if (item->pi == bag->pi) {
+    pi_new = item->pi;
     if (pi_new == NULL) {
-      /* Unlock before creating a new polling island: the polling island will
-         create a workqueue which creates a file descriptor, and holding an fd
-         lock here can eventually cause a loop to appear to TSAN (making it
-         unhappy). We don't think it's a real loop (there's an epoch point where
-         that loop possibility disappears), but the advantages of keeping TSAN
-         happy outweigh any performance advantage we might have by keeping the
-         lock held. */
-      gpr_mu_unlock(&fd->mu);
-      pi_new = polling_island_create(exec_ctx, fd, &error);
-      gpr_mu_lock(&fd->mu);
-      /* Need to reverify any assumptions made between the initial lock and
-         getting to this branch: if they've changed, we need to throw away our
-         work and figure things out again. */
-      if (fd->polling_island != NULL) {
-        GRPC_POLLING_TRACE(
-            "pollset_add_fd: Raced creating new polling island. pi_new: %p "
-            "(fd: %d, pollset: %p)",
-            (void *)pi_new, fd->fd, (void *)pollset);
-
-        /* No need to lock 'pi_new' here since this is a new polling island and
-         * no one has a reference to it yet */
-        polling_island_remove_all_fds_locked(pi_new, true, &error);
-
-        /* Ref and unref so that the polling island gets deleted during unref */
-        PI_ADD_REF(pi_new, "dance_of_destruction");
-        PI_UNREF(exec_ctx, pi_new, "dance_of_destruction");
-        goto retry;
+      /* GPR_ASSERT(item->pi == bag->pi == NULL) */
+
+      /* If we are adding an fd to a bag (i.e pollset or pollset_set), then
+       * we need to do some extra work to make TSAN happy */
+      if (item_type == POLL_OBJ_FD) {
+        /* Unlock before creating a new polling island: the polling island will
+           create a workqueue which creates a file descriptor, and holding an fd
+           lock here can eventually cause a loop to appear to TSAN (making it
+           unhappy). We don't think it's a real loop (there's an epoch point
+           where that loop possibility disappears), but the advantages of
+           keeping TSAN happy outweigh any performance advantage we might have
+           by keeping the lock held. */
+        gpr_mu_unlock(&item->mu);
+        pi_new = polling_island_create(exec_ctx, FD_FROM_PO(item), &error);
+        gpr_mu_lock(&item->mu);
+
+        /* Need to reverify any assumptions made between the initial lock and
+           getting to this branch: if they've changed, we need to throw away our
+           work and figure things out again. */
+        if (item->pi != NULL) {
+          GRPC_POLLING_TRACE(
+              "add_poll_object: Raced creating new polling island. pi_new: %p "
+              "(fd: %d, %s: %p)",
+              (void *)pi_new, FD_FROM_PO(item)->fd, poll_obj_string(bag_type),
+              (void *)bag);
+          /* No need to lock 'pi_new' here since this is a new polling island
+            * and no one has a reference to it yet */
+          polling_island_remove_all_fds_locked(pi_new, true, &error);
+
+          /* Ref and unref so that the polling island gets deleted during unref
+           */
+          PI_ADD_REF(pi_new, "dance_of_destruction");
+          PI_UNREF(exec_ctx, pi_new, "dance_of_destruction");
+          goto retry;
+        }
       } else {
-        GRPC_POLLING_TRACE(
-            "pollset_add_fd: Created new polling island. pi_new: %p (fd: %d, "
-            "pollset: %p)",
-            (void *)pi_new, fd->fd, (void *)pollset);
+        pi_new = polling_island_create(exec_ctx, NULL, &error);
       }
+
+      GRPC_POLLING_TRACE(
+          "add_poll_object: Created new polling island. pi_new: %p (%s: %p, "
+          "%s: %p)",
+          (void *)pi_new, poll_obj_string(item_type), (void *)item,
+          poll_obj_string(bag_type), (void *)bag);
+    } else {
+      GRPC_POLLING_TRACE(
+          "add_poll_object: Same polling island. pi: %p (%s, %s)",
+          (void *)pi_new, poll_obj_string(item_type),
+          poll_obj_string(bag_type));
+    }
+  } else if (item->pi == NULL) {
+    /* GPR_ASSERT(bag->pi != NULL) */
+    /* Make pi_new point to latest pi*/
+    pi_new = polling_island_lock(bag->pi);
+
+    if (item_type == POLL_OBJ_FD) {
+      grpc_fd *fd = FD_FROM_PO(item);
+      polling_island_add_fds_locked(pi_new, &fd, 1, true, &error);
     }
-  } else if (fd->polling_island == NULL) {
-    pi_new = polling_island_lock(pollset->polling_island);
-    polling_island_add_fds_locked(pi_new, &fd, 1, true, &error);
-    gpr_mu_unlock(&pi_new->mu);
 
+    gpr_mu_unlock(&pi_new->mu);
     GRPC_POLLING_TRACE(
-        "pollset_add_fd: fd->pi was NULL. pi_new: %p (fd: %d, pollset: %p, "
-        "pollset->pi: %p)",
-        (void *)pi_new, fd->fd, (void *)pollset,
-        (void *)pollset->polling_island);
-  } else if (pollset->polling_island == NULL) {
-    pi_new = polling_island_lock(fd->polling_island);
+        "add_poll_obj: item->pi was NULL. pi_new: %p (item(%s): %p, "
+        "bag(%s): %p)",
+        (void *)pi_new, poll_obj_string(item_type), (void *)item,
+        poll_obj_string(bag_type), (void *)bag);
+  } else if (bag->pi == NULL) {
+    /* GPR_ASSERT(item->pi != NULL) */
+    /* Make pi_new to point to latest pi */
+    pi_new = polling_island_lock(item->pi);
     gpr_mu_unlock(&pi_new->mu);
-
     GRPC_POLLING_TRACE(
-        "pollset_add_fd: pollset->pi was NULL. pi_new: %p (fd: %d, pollset: "
-        "%p, fd->pi: %p",
-        (void *)pi_new, fd->fd, (void *)pollset, (void *)fd->polling_island);
+        "add_poll_obj: bag->pi was NULL. pi_new: %p (item(%s): %p, "
+        "bag(%s): %p)",
+        (void *)pi_new, poll_obj_string(item_type), (void *)item,
+        poll_obj_string(bag_type), (void *)bag);
   } else {
-    pi_new = polling_island_merge(fd->polling_island, pollset->polling_island,
-                                  &error);
+    pi_new = polling_island_merge(item->pi, bag->pi, &error);
     GRPC_POLLING_TRACE(
-        "pollset_add_fd: polling islands merged. pi_new: %p (fd: %d, pollset: "
-        "%p, fd->pi: %p, pollset->pi: %p)",
-        (void *)pi_new, fd->fd, (void *)pollset, (void *)fd->polling_island,
-        (void *)pollset->polling_island);
+        "add_poll_obj: polling islands merged. pi_new: %p (item(%s): %p, "
+        "bag(%s): %p)",
+        (void *)pi_new, poll_obj_string(item_type), (void *)item,
+        poll_obj_string(bag_type), (void *)bag);
   }
 
-  /* At this point, pi_new is the polling island that both fd->polling_island
-     and pollset->polling_island must be pointing to */
+  /* At this point, pi_new is the polling island that both item->pi and bag->pi
+     MUST be pointing to */
 
-  if (fd->polling_island != pi_new) {
-    PI_ADD_REF(pi_new, "fd");
-    if (fd->polling_island != NULL) {
-      PI_UNREF(exec_ctx, fd->polling_island, "fd");
+  if (item->pi != pi_new) {
+    PI_ADD_REF(pi_new, poll_obj_string(item_type));
+    if (item->pi != NULL) {
+      PI_UNREF(exec_ctx, item->pi, poll_obj_string(item_type));
     }
-    fd->polling_island = pi_new;
+    item->pi = pi_new;
   }
 
-  if (pollset->polling_island != pi_new) {
-    PI_ADD_REF(pi_new, "ps");
-    if (pollset->polling_island != NULL) {
-      PI_UNREF(exec_ctx, pollset->polling_island, "ps");
+  if (bag->pi != pi_new) {
+    PI_ADD_REF(pi_new, poll_obj_string(bag_type));
+    if (bag->pi != NULL) {
+      PI_UNREF(exec_ctx, bag->pi, poll_obj_string(bag_type));
     }
-    pollset->polling_island = pi_new;
+    bag->pi = pi_new;
   }
 
-  gpr_mu_unlock(&fd->mu);
-  gpr_mu_unlock(&pollset->mu);
+  gpr_mu_unlock(&item->mu);
+  gpr_mu_unlock(&bag->mu);
 
-  GRPC_LOG_IF_ERROR("pollset_add_fd", error);
+  GRPC_LOG_IF_ERROR("add_poll_object", error);
+  GPR_TIMER_END("add_poll_object", 0);
+}
 
-  GPR_TIMER_END("pollset_add_fd", 0);
+static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+                           grpc_fd *fd) {
+  add_poll_object(exec_ctx, &pollset->po, POLL_OBJ_POLLSET, &fd->po,
+                  POLL_OBJ_FD);
 }
 
 /*******************************************************************************
@@ -1784,142 +1825,60 @@ retry:
  */
 
 static grpc_pollset_set *pollset_set_create(void) {
-  grpc_pollset_set *pollset_set = gpr_malloc(sizeof(*pollset_set));
-  memset(pollset_set, 0, sizeof(*pollset_set));
-  gpr_mu_init(&pollset_set->mu);
-  return pollset_set;
+  grpc_pollset_set *pss = gpr_malloc(sizeof(*pss));
+  gpr_mu_init(&pss->po.mu);
+  pss->po.pi = NULL;
+#ifdef PO_DEBUG
+  pss->po.obj_type = POLL_OBJ_POLLSET_SET;
+#endif
+  return pss;
 }
 
-static void pollset_set_destroy(grpc_pollset_set *pollset_set) {
-  size_t i;
-  gpr_mu_destroy(&pollset_set->mu);
-  for (i = 0; i < pollset_set->fd_count; i++) {
-    GRPC_FD_UNREF(pollset_set->fds[i], "pollset_set");
+static void pollset_set_destroy(grpc_pollset_set *pss) {
+  gpr_mu_destroy(&pss->po.mu);
+
+  if (pss->po.pi != NULL) {
+    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+    PI_UNREF(&exec_ctx, pss->po.pi, "pss_destroy");
+    grpc_exec_ctx_finish(&exec_ctx);
   }
-  gpr_free(pollset_set->pollsets);
-  gpr_free(pollset_set->pollset_sets);
-  gpr_free(pollset_set->fds);
-  gpr_free(pollset_set);
+
+  gpr_free(pss);
 }
 
-static void pollset_set_add_fd(grpc_exec_ctx *exec_ctx,
-                               grpc_pollset_set *pollset_set, grpc_fd *fd) {
-  size_t i;
-  gpr_mu_lock(&pollset_set->mu);
-  if (pollset_set->fd_count == pollset_set->fd_capacity) {
-    pollset_set->fd_capacity = GPR_MAX(8, 2 * pollset_set->fd_capacity);
-    pollset_set->fds = gpr_realloc(
-        pollset_set->fds, pollset_set->fd_capacity * sizeof(*pollset_set->fds));
-  }
-  GRPC_FD_REF(fd, "pollset_set");
-  pollset_set->fds[pollset_set->fd_count++] = fd;
-  for (i = 0; i < pollset_set->pollset_count; i++) {
-    pollset_add_fd(exec_ctx, pollset_set->pollsets[i], fd);
-  }
-  for (i = 0; i < pollset_set->pollset_set_count; i++) {
-    pollset_set_add_fd(exec_ctx, pollset_set->pollset_sets[i], fd);
-  }
-  gpr_mu_unlock(&pollset_set->mu);
+static void pollset_set_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset_set *pss,
+                               grpc_fd *fd) {
+  add_poll_object(exec_ctx, &pss->po, POLL_OBJ_POLLSET_SET, &fd->po,
+                  POLL_OBJ_FD);
 }
 
-static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
-                               grpc_pollset_set *pollset_set, grpc_fd *fd) {
-  size_t i;
-  gpr_mu_lock(&pollset_set->mu);
-  for (i = 0; i < pollset_set->fd_count; i++) {
-    if (pollset_set->fds[i] == fd) {
-      pollset_set->fd_count--;
-      GPR_SWAP(grpc_fd *, pollset_set->fds[i],
-               pollset_set->fds[pollset_set->fd_count]);
-      GRPC_FD_UNREF(fd, "pollset_set");
-      break;
-    }
-  }
-  for (i = 0; i < pollset_set->pollset_set_count; i++) {
-    pollset_set_del_fd(exec_ctx, pollset_set->pollset_sets[i], fd);
-  }
-  gpr_mu_unlock(&pollset_set->mu);
+static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx, grpc_pollset_set *pss,
+                               grpc_fd *fd) {
+  /* Nothing to do */
 }
 
 static void pollset_set_add_pollset(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset_set *pollset_set,
-                                    grpc_pollset *pollset) {
-  size_t i, j;
-  gpr_mu_lock(&pollset_set->mu);
-  if (pollset_set->pollset_count == pollset_set->pollset_capacity) {
-    pollset_set->pollset_capacity =
-        GPR_MAX(8, 2 * pollset_set->pollset_capacity);
-    pollset_set->pollsets =
-        gpr_realloc(pollset_set->pollsets, pollset_set->pollset_capacity *
-                                               sizeof(*pollset_set->pollsets));
-  }
-  pollset_set->pollsets[pollset_set->pollset_count++] = pollset;
-  for (i = 0, j = 0; i < pollset_set->fd_count; i++) {
-    if (fd_is_orphaned(pollset_set->fds[i])) {
-      GRPC_FD_UNREF(pollset_set->fds[i], "pollset_set");
-    } else {
-      pollset_add_fd(exec_ctx, pollset, pollset_set->fds[i]);
-      pollset_set->fds[j++] = pollset_set->fds[i];
-    }
-  }
-  pollset_set->fd_count = j;
-  gpr_mu_unlock(&pollset_set->mu);
+                                    grpc_pollset_set *pss, grpc_pollset *ps) {
+  add_poll_object(exec_ctx, &pss->po, POLL_OBJ_POLLSET_SET, &ps->po,
+                  POLL_OBJ_POLLSET);
 }
 
 static void pollset_set_del_pollset(grpc_exec_ctx *exec_ctx,
-                                    grpc_pollset_set *pollset_set,
-                                    grpc_pollset *pollset) {
-  size_t i;
-  gpr_mu_lock(&pollset_set->mu);
-  for (i = 0; i < pollset_set->pollset_count; i++) {
-    if (pollset_set->pollsets[i] == pollset) {
-      pollset_set->pollset_count--;
-      GPR_SWAP(grpc_pollset *, pollset_set->pollsets[i],
-               pollset_set->pollsets[pollset_set->pollset_count]);
-      break;
-    }
-  }
-  gpr_mu_unlock(&pollset_set->mu);
+                                    grpc_pollset_set *pss, grpc_pollset *ps) {
+  /* Nothing to do */
 }
 
 static void pollset_set_add_pollset_set(grpc_exec_ctx *exec_ctx,
                                         grpc_pollset_set *bag,
                                         grpc_pollset_set *item) {
-  size_t i, j;
-  gpr_mu_lock(&bag->mu);
-  if (bag->pollset_set_count == bag->pollset_set_capacity) {
-    bag->pollset_set_capacity = GPR_MAX(8, 2 * bag->pollset_set_capacity);
-    bag->pollset_sets =
-        gpr_realloc(bag->pollset_sets,
-                    bag->pollset_set_capacity * sizeof(*bag->pollset_sets));
-  }
-  bag->pollset_sets[bag->pollset_set_count++] = item;
-  for (i = 0, j = 0; i < bag->fd_count; i++) {
-    if (fd_is_orphaned(bag->fds[i])) {
-      GRPC_FD_UNREF(bag->fds[i], "pollset_set");
-    } else {
-      pollset_set_add_fd(exec_ctx, item, bag->fds[i]);
-      bag->fds[j++] = bag->fds[i];
-    }
-  }
-  bag->fd_count = j;
-  gpr_mu_unlock(&bag->mu);
+  add_poll_object(exec_ctx, &bag->po, POLL_OBJ_POLLSET_SET, &item->po,
+                  POLL_OBJ_POLLSET_SET);
 }
 
 static void pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
                                         grpc_pollset_set *bag,
                                         grpc_pollset_set *item) {
-  size_t i;
-  gpr_mu_lock(&bag->mu);
-  for (i = 0; i < bag->pollset_set_count; i++) {
-    if (bag->pollset_sets[i] == item) {
-      bag->pollset_set_count--;
-      GPR_SWAP(grpc_pollset_set *, bag->pollset_sets[i],
-               bag->pollset_sets[bag->pollset_set_count]);
-      break;
-    }
-  }
-  gpr_mu_unlock(&bag->mu);
+  /* Nothing to do */
 }
 
 /* Test helper functions
@@ -1927,9 +1886,9 @@ static void pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
 void *grpc_fd_get_polling_island(grpc_fd *fd) {
   polling_island *pi;
 
-  gpr_mu_lock(&fd->mu);
-  pi = fd->polling_island;
-  gpr_mu_unlock(&fd->mu);
+  gpr_mu_lock(&fd->po.mu);
+  pi = fd->po.pi;
+  gpr_mu_unlock(&fd->po.mu);
 
   return pi;
 }
@@ -1937,9 +1896,9 @@ void *grpc_fd_get_polling_island(grpc_fd *fd) {
 void *grpc_pollset_get_polling_island(grpc_pollset *ps) {
   polling_island *pi;
 
-  gpr_mu_lock(&ps->mu);
-  pi = ps->polling_island;
-  gpr_mu_unlock(&ps->mu);
+  gpr_mu_lock(&ps->po.mu);
+  pi = ps->po.pi;
+  gpr_mu_unlock(&ps->po.mu);
 
   return pi;
 }