Merge pull request #602 from dklempner/unary_promotion_with_concurrent_poll

Ensure there is no concurrent poller for unary->multipoll

src/core/iomgr/fd_posix.c

@@ -38,6 +38,7 @@
 #include "src/core/iomgr/fd_posix.h"
 
 #include <assert.h>
+#include <sys/socket.h>
 #include <unistd.h>
 
 #include "src/core/iomgr/iomgr_internal.h"
@@ -113,6 +114,7 @@ static void ref_by(grpc_fd *fd, int n) {
 static void unref_by(grpc_fd *fd, int n) {
   gpr_atm old = gpr_atm_full_fetch_add(&fd->refst, -n);
   if (old == n) {
+    close(fd->fd);
     grpc_iomgr_add_callback(fd->on_done, fd->on_done_user_data);
     freelist_fd(fd);
     grpc_iomgr_unref();
@@ -158,9 +160,9 @@ static void wake_watchers(grpc_fd *fd) {
 void grpc_fd_orphan(grpc_fd *fd, grpc_iomgr_cb_func on_done, void *user_data) {
   fd->on_done = on_done ? on_done : do_nothing;
   fd->on_done_user_data = user_data;
+  shutdown(fd->fd, SHUT_RDWR);
   ref_by(fd, 1); /* remove active status, but keep referenced */
   wake_watchers(fd);
-  close(fd->fd);
   unref_by(fd, 2); /* drop the reference */
 }
 

src/core/iomgr/pollset.h

@@ -52,9 +52,14 @@
 #include "src/core/iomgr/pollset_windows.h"
 #endif
 
+
 void grpc_pollset_init(grpc_pollset *pollset);
+void grpc_pollset_shutdown(grpc_pollset *pollset,
+                           void (*shutdown_done)(void *arg),
+                           void *shutdown_done_arg);
 void grpc_pollset_destroy(grpc_pollset *pollset);
 
+
 /* Do some work on a pollset.
    May involve invoking asynchronous callbacks, or actually polling file
    descriptors.

src/core/iomgr/pollset_posix.c

@@ -55,6 +55,7 @@
 static grpc_pollset g_backup_pollset;
 static int g_shutdown_backup_poller;
 static gpr_event g_backup_poller_done;
+static gpr_event g_backup_pollset_shutdown_done;
 
 static void backup_poller(void *p) {
   gpr_timespec delta = gpr_time_from_millis(100);
@@ -104,9 +105,14 @@ void grpc_pollset_global_init(void) {
   /* start the backup poller thread */
   g_shutdown_backup_poller = 0;
   gpr_event_init(&g_backup_poller_done);
+  gpr_event_init(&g_backup_pollset_shutdown_done);
   gpr_thd_new(&id, backup_poller, NULL, NULL);
 }
 
+static void on_backup_pollset_shutdown_done(void *arg) {
+  gpr_event_set(&g_backup_pollset_shutdown_done, (void *)1);
+}
+
 void grpc_pollset_global_shutdown(void) {
   /* terminate the backup poller thread */
   gpr_mu_lock(&g_backup_pollset.mu);
@@ -114,6 +120,10 @@ void grpc_pollset_global_shutdown(void) {
   gpr_mu_unlock(&g_backup_pollset.mu);
   gpr_event_wait(&g_backup_poller_done, gpr_inf_future);
 
+  grpc_pollset_shutdown(&g_backup_pollset, on_backup_pollset_shutdown_done,
+                        NULL);
+  gpr_event_wait(&g_backup_pollset_shutdown_done, gpr_inf_future);
+
   /* destroy the backup pollset */
   grpc_pollset_destroy(&g_backup_pollset);
 
@@ -130,6 +140,8 @@ void grpc_pollset_init(grpc_pollset *pollset) {
   gpr_mu_init(&pollset->mu);
   gpr_cv_init(&pollset->cv);
   grpc_pollset_kick_init(&pollset->kick_state);
+  pollset->in_flight_cbs = 0;
+  pollset->shutting_down = 0;
   become_empty_pollset(pollset);
 }
 
@@ -163,7 +175,24 @@ int grpc_pollset_work(grpc_pollset *pollset, gpr_timespec deadline) {
   return pollset->vtable->maybe_work(pollset, deadline, now, 1);
 }
 
+void grpc_pollset_shutdown(grpc_pollset *pollset,
+                           void (*shutdown_done)(void *arg),
+                           void *shutdown_done_arg) {
+  int in_flight_cbs;
+  gpr_mu_lock(&pollset->mu);
+  pollset->shutting_down = 1;
+  in_flight_cbs = pollset->in_flight_cbs;
+  pollset->shutdown_done_cb = shutdown_done;
+  pollset->shutdown_done_arg = shutdown_done_arg;
+  gpr_mu_unlock(&pollset->mu);
+  if (in_flight_cbs == 0) {
+    shutdown_done(shutdown_done_arg);
+  }
+}
+
 void grpc_pollset_destroy(grpc_pollset *pollset) {
+  GPR_ASSERT(pollset->shutting_down);
+  GPR_ASSERT(pollset->in_flight_cbs == 0);
   pollset->vtable->destroy(pollset);
   grpc_pollset_kick_destroy(&pollset->kick_state);
   gpr_mu_destroy(&pollset->mu);
@@ -201,21 +230,119 @@ static void become_empty_pollset(grpc_pollset *pollset) {
  *                      via poll()
  */
 
+
+typedef struct grpc_unary_promote_args {
+  const grpc_pollset_vtable *original_vtable;
+  grpc_pollset *pollset;
+  grpc_fd *fd;
+} grpc_unary_promote_args;
+
+static void unary_poll_do_promote(void *args, int success) {
+  grpc_unary_promote_args *up_args = args;
+  const grpc_pollset_vtable *original_vtable = up_args->original_vtable;
+  grpc_pollset *pollset = up_args->pollset;
+  grpc_fd *fd = up_args->fd;
+  int do_shutdown_cb = 0;
+  gpr_free(up_args);
+
+  /*
+   * This is quite tricky. There are a number of cases to keep in mind here:
+   * 1. fd may have been orphaned
+   * 2. The pollset may no longer be a unary poller (and we can't let case #1
+   * leak to other pollset types!)
+   * 3. pollset's fd (which may have changed) may have been orphaned
+   * 4. The pollset may be shutting down.
+   */
+
+  gpr_mu_lock(&pollset->mu);
+  /* First we need to ensure that nobody is polling concurrently */
+  while (pollset->counter != 0) {
+    grpc_pollset_kick(pollset);
+    gpr_cv_wait(&pollset->cv, &pollset->mu, gpr_inf_future);
+  }
+  /* At this point the pollset may no longer be a unary poller. In that case
+   * we should just call the right add function and be done. */
+  /* TODO(klempner): If we're not careful this could cause infinite recursion.
+   * That's not a problem for now because empty_pollset has a trivial poller
+   * and we don't have any mechanism to unbecome multipoller. */
+  pollset->in_flight_cbs--;
+  if (pollset->shutting_down) {
+    gpr_log(GPR_INFO, "Shutting down");
+    /* We don't care about this pollset anymore. */
+    if (pollset->in_flight_cbs == 0) {
+      do_shutdown_cb = 1;
+    }
+  } else if (grpc_fd_is_orphaned(fd)) {
+    /* Don't try to add it to anything, we'll drop our ref on it below */
+  } else if (pollset->vtable != original_vtable) {
+    gpr_log(GPR_INFO, "Not original vtable");
+    pollset->vtable->add_fd(pollset, fd);
+  } else if (fd != pollset->data.ptr) {
+    grpc_fd *fds[2];
+    fds[0] = pollset->data.ptr;
+    fds[1] = fd;
+
+    if (!grpc_fd_is_orphaned(fds[0])) {
+      grpc_platform_become_multipoller(pollset, fds, GPR_ARRAY_SIZE(fds));
+      grpc_fd_unref(fds[0]);
+    } else {
+      /* old fd is orphaned and we haven't cleaned it up until now, so remain a
+       * unary poller */
+      /* Note that it is possible that fds[1] is also orphaned at this point.
+       * That's okay, we'll correct it at the next add or poll. */
+      grpc_fd_unref(fds[0]);
+      pollset->data.ptr = fd;
+      grpc_fd_ref(fd);
+    }
+  }
+
+  gpr_cv_broadcast(&pollset->cv);
+  gpr_mu_unlock(&pollset->mu);
+
+  if (do_shutdown_cb) {
+    pollset->shutdown_done_cb(pollset->shutdown_done_arg);
+  }
+
+  /* Matching ref in unary_poll_pollset_add_fd */
+  grpc_fd_unref(fd);
+}
+
 static void unary_poll_pollset_add_fd(grpc_pollset *pollset, grpc_fd *fd) {
-  grpc_fd *fds[2];
+  grpc_unary_promote_args *up_args;
   if (fd == pollset->data.ptr) return;
-  fds[0] = pollset->data.ptr;
-  fds[1] = fd;
-  if (!grpc_fd_is_orphaned(fds[0])) {
-    grpc_platform_become_multipoller(pollset, fds, GPR_ARRAY_SIZE(fds));
-    grpc_fd_unref(fds[0]);
-  } else {
-    /* old fd is orphaned and we haven't cleaned it up until now, so remain a
-     * unary poller */
-    grpc_fd_unref(fds[0]);
-    pollset->data.ptr = fd;
-    grpc_fd_ref(fd);
+
+  if (!pollset->counter) {
+    /* Fast path -- no in flight cbs */
+    /* TODO(klempner): Comment this out and fix any test failures or establish
+     * they are due to timing issues */
+    grpc_fd *fds[2];
+    fds[0] = pollset->data.ptr;
+    fds[1] = fd;
+
+    if (!grpc_fd_is_orphaned(fds[0])) {
+      grpc_platform_become_multipoller(pollset, fds, GPR_ARRAY_SIZE(fds));
+      grpc_fd_unref(fds[0]);
+    } else {
+      /* old fd is orphaned and we haven't cleaned it up until now, so remain a
+       * unary poller */
+      grpc_fd_unref(fds[0]);
+      pollset->data.ptr = fd;
+      grpc_fd_ref(fd);
+    }
+    return;
   }
+
+  /* Now we need to promote. This needs to happen when we're not polling. Since
+   * this may be called from poll, the wait needs to happen asynchronously. */
+  grpc_fd_ref(fd);
+  pollset->in_flight_cbs++;
+  up_args = gpr_malloc(sizeof(*up_args));
+  up_args->pollset = pollset;
+  up_args->fd = fd;
+  up_args->original_vtable = pollset->vtable;
+  grpc_iomgr_add_callback(unary_poll_do_promote, up_args);
+
+  grpc_pollset_kick(pollset);
 }
 
 static void unary_poll_pollset_del_fd(grpc_pollset *pollset, grpc_fd *fd) {
@@ -238,6 +365,10 @@ static int unary_poll_pollset_maybe_work(grpc_pollset *pollset,
   if (pollset->counter) {
     return 0;
   }
+  if (pollset->in_flight_cbs) {
+    /* Give do_promote priority so we don't starve it out */
+    return 0;
+  }
   fd = pollset->data.ptr;
   if (grpc_fd_is_orphaned(fd)) {
     grpc_fd_unref(fd);

src/core/iomgr/pollset_posix.h

@@ -55,6 +55,10 @@ typedef struct grpc_pollset {
   gpr_cv cv;
   grpc_pollset_kick_state kick_state;
   int counter;
+  int in_flight_cbs;
+  int shutting_down;
+  void (*shutdown_done_cb)(void *arg);
+  void *shutdown_done_arg;
   union {
     int fd;
     void *ptr;

src/core/iomgr/pollset_windows.c

@@ -46,6 +46,12 @@ void grpc_pollset_init(grpc_pollset *pollset) {
   gpr_cv_init(&pollset->cv);
 }
 
+void grpc_pollset_shutdown(grpc_pollset *pollset,
+                           void (*shutdown_done)(void *arg),
+                           void *shutdown_done_arg) {
+  shutdown_done(shutdown_done_arg);
+}
+
 void grpc_pollset_destroy(grpc_pollset *pollset) {
   gpr_mu_destroy(&pollset->mu);
   gpr_cv_destroy(&pollset->cv);

src/core/surface/completion_queue.c

@@ -389,12 +389,17 @@ void grpc_completion_queue_shutdown(grpc_completion_queue *cc) {
   }
 }
 
-void grpc_completion_queue_destroy(grpc_completion_queue *cc) {
-  GPR_ASSERT(cc->queue == NULL);
+static void on_pollset_destroy_done(void *arg) {
+  grpc_completion_queue *cc = arg;
   grpc_pollset_destroy(&cc->pollset);
   gpr_free(cc);
 }
 
+void grpc_completion_queue_destroy(grpc_completion_queue *cc) {
+  GPR_ASSERT(cc->queue == NULL);
+  grpc_pollset_shutdown(&cc->pollset, on_pollset_destroy_done, cc);
+}
+
 void grpc_event_finish(grpc_event *base) {
   event *ev = (event *)base;
   ev->on_finish(ev->on_finish_user_data, GRPC_OP_OK);