--- /dev/null
+/*
+ *
+ * Copyright 2015 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_EXEC_CTX_H
+#define GRPC_CORE_LIB_IOMGR_EXEC_CTX_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/impl/codegen/grpc_types.h>
+#include <grpc/support/atm.h>
+#include <grpc/support/cpu.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/gpr/time_precise.h"
+#include "src/core/lib/gpr/tls.h"
+#include "src/core/lib/gprpp/fork.h"
+#include "src/core/lib/iomgr/closure.h"
+
+typedef int64_t grpc_millis;
+
+#define GRPC_MILLIS_INF_FUTURE INT64_MAX
+#define GRPC_MILLIS_INF_PAST INT64_MIN
+
+/** A combiner represents a list of work to be executed later.
+ Forward declared here to avoid a circular dependency with combiner.h. */
+typedef struct grpc_combiner grpc_combiner;
+
+/* This exec_ctx is ready to return: either pre-populated, or cached as soon as
+ the finish_check returns true */
+#define GRPC_EXEC_CTX_FLAG_IS_FINISHED 1
+/* The exec_ctx's thread is (potentially) owned by a call or channel: care
+ should be given to not delete said call/channel from this exec_ctx */
+#define GRPC_EXEC_CTX_FLAG_THREAD_RESOURCE_LOOP 2
+/* This exec ctx was initialized by an internal thread, and should not
+ be counted by fork handlers */
+#define GRPC_EXEC_CTX_FLAG_IS_INTERNAL_THREAD 4
+
+/* This application callback exec ctx was initialized by an internal thread, and
+ should not be counted by fork handlers */
+#define GRPC_APP_CALLBACK_EXEC_CTX_FLAG_IS_INTERNAL_THREAD 1
+
+extern grpc_closure_scheduler* grpc_schedule_on_exec_ctx;
+
+gpr_timespec grpc_millis_to_timespec(grpc_millis millis, gpr_clock_type clock);
+grpc_millis grpc_timespec_to_millis_round_down(gpr_timespec timespec);
+grpc_millis grpc_timespec_to_millis_round_up(gpr_timespec timespec);
+grpc_millis grpc_cycle_counter_to_millis_round_down(gpr_cycle_counter cycles);
+grpc_millis grpc_cycle_counter_to_millis_round_up(gpr_cycle_counter cycles);
+
+namespace grpc_core {
+/** Execution context.
+ * A bag of data that collects information along a callstack.
+ * It is created on the stack at core entry points (public API or iomgr), and
+ * stored internally as a thread-local variable.
+ *
+ * Generally, to create an exec_ctx instance, add the following line at the top
+ * of the public API entry point or at the start of a thread's work function :
+ *
+ * grpc_core::ExecCtx exec_ctx;
+ *
+ * Access the created ExecCtx instance using :
+ * grpc_core::ExecCtx::Get()
+ *
+ * Specific responsibilities (this may grow in the future):
+ * - track a list of core work that needs to be delayed until the base of the
+ * call stack (this provides a convenient mechanism to run callbacks
+ * without worrying about locking issues)
+ * - provide a decision maker (via IsReadyToFinish) that provides a
+ * signal as to whether a borrowed thread should continue to do work or
+ * should actively try to finish up and get this thread back to its owner
+ *
+ * CONVENTIONS:
+ * - Instance of this must ALWAYS be constructed on the stack, never
+ * heap allocated.
+ * - Do not pass exec_ctx as a parameter to a function. Always access it using
+ * grpc_core::ExecCtx::Get().
+ * - NOTE: In the future, the convention is likely to change to allow only one
+ * ExecCtx on a thread's stack at the same time. The TODO below
+ * discusses this plan in more detail.
+ *
+ * TODO(yashykt): Only allow one "active" ExecCtx on a thread at the same time.
+ * Stage 1: If a new one is created on the stack, it should just
+ * pass-through to the underlying ExecCtx deeper in the thread's
+ * stack.
+ * Stage 2: Assert if a 2nd one is ever created on the stack
+ * since that implies a core re-entry outside of application
+ * callbacks.
+ */
+class ExecCtx {
+ public:
+ /** Default Constructor */
+
+ ExecCtx() : flags_(GRPC_EXEC_CTX_FLAG_IS_FINISHED) {
+ grpc_core::Fork::IncExecCtxCount();
+ Set(this);
+ }
+
+ /** Parameterised Constructor */
+ ExecCtx(uintptr_t fl) : flags_(fl) {
+ if (!(GRPC_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags_)) {
+ grpc_core::Fork::IncExecCtxCount();
+ }
+ Set(this);
+ }
+
+ /** Destructor */
+ virtual ~ExecCtx() {
+ flags_ |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
+ Flush();
+ Set(last_exec_ctx_);
+ if (!(GRPC_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags_)) {
+ grpc_core::Fork::DecExecCtxCount();
+ }
+ }
+
+ /** Disallow copy and assignment operators */
+ ExecCtx(const ExecCtx&) = delete;
+ ExecCtx& operator=(const ExecCtx&) = delete;
+
+ unsigned starting_cpu() const { return starting_cpu_; }
+
+ struct CombinerData {
+ /* currently active combiner: updated only via combiner.c */
+ grpc_combiner* active_combiner;
+ /* last active combiner in the active combiner list */
+ grpc_combiner* last_combiner;
+ };
+
+ /** Only to be used by grpc-combiner code */
+ CombinerData* combiner_data() { return &combiner_data_; }
+
+ /** Return pointer to grpc_closure_list */
+ grpc_closure_list* closure_list() { return &closure_list_; }
+
+ /** Return flags */
+ uintptr_t flags() { return flags_; }
+
+ /** Checks if there is work to be done */
+ bool HasWork() {
+ return combiner_data_.active_combiner != nullptr ||
+ !grpc_closure_list_empty(closure_list_);
+ }
+
+ /** Flush any work that has been enqueued onto this grpc_exec_ctx.
+ * Caller must guarantee that no interfering locks are held.
+ * Returns true if work was performed, false otherwise.
+ */
+ bool Flush();
+
+ /** Returns true if we'd like to leave this execution context as soon as
+ * possible: useful for deciding whether to do something more or not
+ * depending on outside context.
+ */
+ bool IsReadyToFinish() {
+ if ((flags_ & GRPC_EXEC_CTX_FLAG_IS_FINISHED) == 0) {
+ if (CheckReadyToFinish()) {
+ flags_ |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
+ return true;
+ }
+ return false;
+ } else {
+ return true;
+ }
+ }
+
+ /** Returns the stored current time relative to start if valid,
+ * otherwise refreshes the stored time, sets it valid and returns the new
+ * value.
+ */
+ grpc_millis Now();
+
+ /** Invalidates the stored time value. A new time value will be set on calling
+ * Now().
+ */
+ void InvalidateNow() { now_is_valid_ = false; }
+
+ /** To be used only by shutdown code in iomgr */
+ void SetNowIomgrShutdown() {
+ now_ = GRPC_MILLIS_INF_FUTURE;
+ now_is_valid_ = true;
+ }
+
+ /** To be used only for testing.
+ * Sets the now value.
+ */
+ void TestOnlySetNow(grpc_millis new_val) {
+ now_ = new_val;
+ now_is_valid_ = true;
+ }
+
+ static void TestOnlyGlobalInit(gpr_timespec new_val);
+
+ /** Global initialization for ExecCtx. Called by iomgr. */
+ static void GlobalInit(void);
+
+ /** Global shutdown for ExecCtx. Called by iomgr. */
+ static void GlobalShutdown(void) { gpr_tls_destroy(&exec_ctx_); }
+
+ /** Gets pointer to current exec_ctx. */
+ static ExecCtx* Get() {
+ return reinterpret_cast<ExecCtx*>(gpr_tls_get(&exec_ctx_));
+ }
+
+ static void Set(ExecCtx* exec_ctx) {
+ gpr_tls_set(&exec_ctx_, reinterpret_cast<intptr_t>(exec_ctx));
+ }
+
+ protected:
+ /** Check if ready to finish. */
+ virtual bool CheckReadyToFinish() { return false; }
+
+ /** Disallow delete on ExecCtx. */
+ static void operator delete(void* p) { abort(); }
+
+ private:
+ /** Set exec_ctx_ to exec_ctx. */
+
+ grpc_closure_list closure_list_ = GRPC_CLOSURE_LIST_INIT;
+ CombinerData combiner_data_ = {nullptr, nullptr};
+ uintptr_t flags_;
+
+ unsigned starting_cpu_ = gpr_cpu_current_cpu();
+
+ bool now_is_valid_ = false;
+ grpc_millis now_ = 0;
+
+ GPR_TLS_CLASS_DECL(exec_ctx_);
+ ExecCtx* last_exec_ctx_ = Get();
+};
+
+/** Application-callback execution context.
+ * A bag of data that collects information along a callstack.
+ * It is created on the stack at core entry points, and stored internally
+ * as a thread-local variable.
+ *
+ * There are three key differences between this structure and ExecCtx:
+ * 1. ApplicationCallbackExecCtx builds a list of application-level
+ * callbacks, but ExecCtx builds a list of internal callbacks to invoke.
+ * 2. ApplicationCallbackExecCtx invokes its callbacks only at destruction;
+ * there is no explicit Flush method.
+ * 3. If more than one ApplicationCallbackExecCtx is created on the thread's
+ * stack, only the one closest to the base of the stack is actually
+ * active and this is the only one that enqueues application callbacks.
+ * (Unlike ExecCtx, it is not feasible to prevent multiple of these on the
+ * stack since the executing application callback may itself enter core.
+ * However, the new one created will just pass callbacks through to the
+ * base one and those will not be executed until the return to the
+ * destructor of the base one, preventing unlimited stack growth.)
+ *
+ * This structure exists because application callbacks may themselves cause a
+ * core re-entry (e.g., through a public API call) and if that call in turn
+ * causes another application-callback, there could be arbitrarily growing
+ * stacks of core re-entries. Instead, any application callbacks instead should
+ * not be invoked until other core work is done and other application callbacks
+ * have completed. To accomplish this, any application callback should be
+ * enqueued using grpc_core::ApplicationCallbackExecCtx::Enqueue .
+ *
+ * CONVENTIONS:
+ * - Instances of this must ALWAYS be constructed on the stack, never
+ * heap allocated.
+ * - Instances of this are generally constructed before ExecCtx when needed.
+ * The only exception is for ExecCtx's that are explicitly flushed and
+ * that survive beyond the scope of the function that can cause application
+ * callbacks to be invoked (e.g., in the timer thread).
+ *
+ * Generally, core entry points that may trigger application-level callbacks
+ * will have the following declarations:
+ *
+ * grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
+ * grpc_core::ExecCtx exec_ctx;
+ *
+ * This ordering is important to make sure that the ApplicationCallbackExecCtx
+ * is destroyed after the ExecCtx (to prevent the re-entry problem described
+ * above, as well as making sure that ExecCtx core callbacks are invoked first)
+ *
+ */
+
+class ApplicationCallbackExecCtx {
+ public:
+ /** Default Constructor */
+ ApplicationCallbackExecCtx() { Set(this, flags_); }
+
+ /** Parameterised Constructor */
+ ApplicationCallbackExecCtx(uintptr_t fl) : flags_(fl) { Set(this, flags_); }
+
+ ~ApplicationCallbackExecCtx() {
+ if (reinterpret_cast<ApplicationCallbackExecCtx*>(
+ gpr_tls_get(&callback_exec_ctx_)) == this) {
+ while (head_ != nullptr) {
+ auto* f = head_;
+ head_ = f->internal_next;
+ if (f->internal_next == nullptr) {
+ tail_ = nullptr;
+ }
+ (*f->functor_run)(f, f->internal_success);
+ }
+ gpr_tls_set(&callback_exec_ctx_, reinterpret_cast<intptr_t>(nullptr));
+ if (!(GRPC_APP_CALLBACK_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags_)) {
+ grpc_core::Fork::DecExecCtxCount();
+ }
+ } else {
+ GPR_DEBUG_ASSERT(head_ == nullptr);
+ GPR_DEBUG_ASSERT(tail_ == nullptr);
+ }
+ }
+
+ static void Set(ApplicationCallbackExecCtx* exec_ctx, uintptr_t flags) {
+ if (reinterpret_cast<ApplicationCallbackExecCtx*>(
+ gpr_tls_get(&callback_exec_ctx_)) == nullptr) {
+ if (!(GRPC_APP_CALLBACK_EXEC_CTX_FLAG_IS_INTERNAL_THREAD & flags)) {
+ grpc_core::Fork::IncExecCtxCount();
+ }
+ gpr_tls_set(&callback_exec_ctx_, reinterpret_cast<intptr_t>(exec_ctx));
+ }
+ }
+
+ static void Enqueue(grpc_experimental_completion_queue_functor* functor,
+ int is_success) {
+ functor->internal_success = is_success;
+ functor->internal_next = nullptr;
+
+ auto* ctx = reinterpret_cast<ApplicationCallbackExecCtx*>(
+ gpr_tls_get(&callback_exec_ctx_));
+
+ if (ctx->head_ == nullptr) {
+ ctx->head_ = functor;
+ }
+ if (ctx->tail_ != nullptr) {
+ ctx->tail_->internal_next = functor;
+ }
+ ctx->tail_ = functor;
+ }
+
+ /** Global initialization for ApplicationCallbackExecCtx. Called by init. */
+ static void GlobalInit(void) { gpr_tls_init(&callback_exec_ctx_); }
+
+ /** Global shutdown for ApplicationCallbackExecCtx. Called by init. */
+ static void GlobalShutdown(void) { gpr_tls_destroy(&callback_exec_ctx_); }
+
+ private:
+ uintptr_t flags_{0u};
+ grpc_experimental_completion_queue_functor* head_{nullptr};
+ grpc_experimental_completion_queue_functor* tail_{nullptr};
+ GPR_TLS_CLASS_DECL(callback_exec_ctx_);
+};
+} // namespace grpc_core
+
+#endif /* GRPC_CORE_LIB_IOMGR_EXEC_CTX_H */
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