Changes for C to C++. Adding extern C to header files for compatibility.

Also converting to .cc

1 files changed, 241 insertions, 0 deletions

diff --git a/src/core/lib/iomgr/lockfree_event.cc b/src/core/lib/iomgr/lockfree_event.cc
new file mode 100644
index 0000000000..f967b22ba9
--- /dev/null
+++ b/src/core/lib/iomgr/lockfree_event.cc
@@ -0,0 +1,241 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/iomgr/lockfree_event.h"
+
+#include <grpc/support/log.h>
+
+#include "src/core/lib/debug/trace.h"
+
+extern grpc_tracer_flag grpc_polling_trace;
+
+/* 'state' holds the to call when the fd is readable or writable respectively.
+   It can contain one of the following values:
+     CLOSURE_READY     : The fd has an I/O event of interest but there is no
+                         closure yet to execute
+
+     CLOSURE_NOT_READY : The fd has no I/O event of interest
+
+     closure ptr       : The closure to be executed when the fd has an I/O
+                         event of interest
+
+     shutdown_error | FD_SHUTDOWN_BIT :
+                        'shutdown_error' field ORed with FD_SHUTDOWN_BIT.
+                         This indicates that the fd is shutdown. Since all
+                         memory allocations are word-aligned, the lower two
+                         bits of the shutdown_error pointer are always 0. So
+                         it is safe to OR these with FD_SHUTDOWN_BIT
+
+   Valid state transitions:
+
+     <closure ptr> <-----3------ CLOSURE_NOT_READY ----1---->  CLOSURE_READY
+       |  |                         ^   |    ^                         |  |
+       |  |                         |   |    |                         |  |
+       |  +--------------4----------+   6    +---------2---------------+  |
+       |                                |                                 |
+       |                                v                                 |
+       +-----5------->  [shutdown_error | FD_SHUTDOWN_BIT] <----7---------+
+
+    For 1, 4 : See grpc_lfev_set_ready() function
+    For 2, 3 : See grpc_lfev_notify_on() function
+    For 5,6,7: See grpc_lfev_set_shutdown() function */
+
+#define CLOSURE_NOT_READY ((gpr_atm)0)
+#define CLOSURE_READY ((gpr_atm)2)
+
+#define FD_SHUTDOWN_BIT ((gpr_atm)1)
+
+void grpc_lfev_init(gpr_atm *state) {
+  gpr_atm_no_barrier_store(state, CLOSURE_NOT_READY);
+}
+
+void grpc_lfev_destroy(gpr_atm *state) {
+  gpr_atm curr = gpr_atm_no_barrier_load(state);
+  if (curr & FD_SHUTDOWN_BIT) {
+    GRPC_ERROR_UNREF((grpc_error *)(curr & ~FD_SHUTDOWN_BIT));
+  } else {
+    GPR_ASSERT(curr == CLOSURE_NOT_READY || curr == CLOSURE_READY);
+  }
+}
+
+bool grpc_lfev_is_shutdown(gpr_atm *state) {
+  gpr_atm curr = gpr_atm_no_barrier_load(state);
+  return (curr & FD_SHUTDOWN_BIT) != 0;
+}
+
+void grpc_lfev_notify_on(grpc_exec_ctx *exec_ctx, gpr_atm *state,
+                         grpc_closure *closure, const char *variable) {
+  while (true) {
+    gpr_atm curr = gpr_atm_no_barrier_load(state);
+    if (GRPC_TRACER_ON(grpc_polling_trace)) {
+      gpr_log(GPR_ERROR, "lfev_notify_on[%s]: %p curr=%p closure=%p", variable,
+              state, (void *)curr, closure);
+    }
+    switch (curr) {
+      case CLOSURE_NOT_READY: {
+        /* CLOSURE_NOT_READY -> <closure>.
+
+           We're guaranteed by API that there's an acquire barrier before here,
+           so there's no need to double-dip and this can be a release-only.
+
+           The release itself pairs with the acquire half of a set_ready full
+           barrier. */
+        if (gpr_atm_rel_cas(state, CLOSURE_NOT_READY, (gpr_atm)closure)) {
+          return; /* Successful. Return */
+        }
+
+        break; /* retry */
+      }
+
+      case CLOSURE_READY: {
+        /* Change the state to CLOSURE_NOT_READY. Schedule the closure if
+           successful. If not, the state most likely transitioned to shutdown.
+           We should retry.
+
+           This can be a no-barrier cas since the state is being transitioned to
+           CLOSURE_NOT_READY; set_ready and set_shutdown do not schedule any
+           closure when transitioning out of CLOSURE_NO_READY state (i.e there
+           is no other code that needs to 'happen-after' this) */
+        if (gpr_atm_no_barrier_cas(state, CLOSURE_READY, CLOSURE_NOT_READY)) {
+          GRPC_CLOSURE_SCHED(exec_ctx, closure, GRPC_ERROR_NONE);
+          return; /* Successful. Return */
+        }
+
+        break; /* retry */
+      }
+
+      default: {
+        /* 'curr' is either a closure or the fd is shutdown(in which case 'curr'
+           contains a pointer to the shutdown-error). If the fd is shutdown,
+           schedule the closure with the shutdown error */
+        if ((curr & FD_SHUTDOWN_BIT) > 0) {
+          grpc_error *shutdown_err = (grpc_error *)(curr & ~FD_SHUTDOWN_BIT);
+          GRPC_CLOSURE_SCHED(exec_ctx, closure,
+                             GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
+                                 "FD Shutdown", &shutdown_err, 1));
+          return;
+        }
+
+        /* There is already a closure!. This indicates a bug in the code */
+        gpr_log(GPR_ERROR,
+                "notify_on called with a previous callback still pending");
+        abort();
+      }
+    }
+  }
+
+  GPR_UNREACHABLE_CODE(return );
+}
+
+bool grpc_lfev_set_shutdown(grpc_exec_ctx *exec_ctx, gpr_atm *state,
+                            grpc_error *shutdown_err) {
+  gpr_atm new_state = (gpr_atm)shutdown_err | FD_SHUTDOWN_BIT;
+
+  while (true) {
+    gpr_atm curr = gpr_atm_no_barrier_load(state);
+    if (GRPC_TRACER_ON(grpc_polling_trace)) {
+      gpr_log(GPR_ERROR, "lfev_set_shutdown: %p curr=%p err=%s", state,
+              (void *)curr, grpc_error_string(shutdown_err));
+    }
+    switch (curr) {
+      case CLOSURE_READY:
+      case CLOSURE_NOT_READY:
+        /* Need a full barrier here so that the initial load in notify_on
+           doesn't need a barrier */
+        if (gpr_atm_full_cas(state, curr, new_state)) {
+          return true; /* early out */
+        }
+        break; /* retry */
+
+      default: {
+        /* 'curr' is either a closure or the fd is already shutdown */
+
+        /* If fd is already shutdown, we are done */
+        if ((curr & FD_SHUTDOWN_BIT) > 0) {
+          GRPC_ERROR_UNREF(shutdown_err);
+          return false;
+        }
+
+        /* Fd is not shutdown. Schedule the closure and move the state to
+           shutdown state.
+           Needs an acquire to pair with setting the closure (and get a
+           happens-after on that edge), and a release to pair with anything
+           loading the shutdown state. */
+        if (gpr_atm_full_cas(state, curr, new_state)) {
+          GRPC_CLOSURE_SCHED(exec_ctx, (grpc_closure *)curr,
+                             GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
+                                 "FD Shutdown", &shutdown_err, 1));
+          return true;
+        }
+
+        /* 'curr' was a closure but now changed to a different state. We will
+          have to retry */
+        break;
+      }
+    }
+  }
+
+  GPR_UNREACHABLE_CODE(return false);
+}
+
+void grpc_lfev_set_ready(grpc_exec_ctx *exec_ctx, gpr_atm *state,
+                         const char *variable) {
+  while (true) {
+    gpr_atm curr = gpr_atm_no_barrier_load(state);
+
+    if (GRPC_TRACER_ON(grpc_polling_trace)) {
+      gpr_log(GPR_ERROR, "lfev_set_ready[%s]: %p curr=%p", variable, state,
+              (void *)curr);
+    }
+
+    switch (curr) {
+      case CLOSURE_READY: {
+        /* Already ready. We are done here */
+        return;
+      }
+
+      case CLOSURE_NOT_READY: {
+        /* No barrier required as we're transitioning to a state that does not
+           involve a closure */
+        if (gpr_atm_no_barrier_cas(state, CLOSURE_NOT_READY, CLOSURE_READY)) {
+          return; /* early out */
+        }
+        break; /* retry */
+      }
+
+      default: {
+        /* 'curr' is either a closure or the fd is shutdown */
+        if ((curr & FD_SHUTDOWN_BIT) > 0) {
+          /* The fd is shutdown. Do nothing */
+          return;
+        }
+        /* Full cas: acquire pairs with this cas' release in the event of a
+           spurious set_ready; release pairs with this or the acquire in
+           notify_on (or set_shutdown) */
+        else if (gpr_atm_full_cas(state, curr, CLOSURE_NOT_READY)) {
+          GRPC_CLOSURE_SCHED(exec_ctx, (grpc_closure *)curr, GRPC_ERROR_NONE);
+          return;
+        }
+        /* else the state changed again (only possible by either a racing
+           set_ready or set_shutdown functions. In both these cases, the closure
+           would have been scheduled for execution. So we are done here */
+        return;
+      }
+    }
+  }
+}