1 // Copyright 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #ifndef MOJO_EDK_SYSTEM_DISPATCHER_H_
6 #define MOJO_EDK_SYSTEM_DISPATCHER_H_
13 #include "base/macros.h"
14 #include "base/memory/ref_counted.h"
15 #include "base/memory/scoped_ptr.h"
16 #include "base/synchronization/lock.h"
17 #include "mojo/edk/embedder/platform_handle.h"
18 #include "mojo/edk/embedder/platform_handle_vector.h"
19 #include "mojo/edk/system/handle_signals_state.h"
20 #include "mojo/edk/system/memory.h"
21 #include "mojo/edk/system/system_impl_export.h"
22 #include "mojo/public/c/system/buffer.h"
23 #include "mojo/public/c/system/data_pipe.h"
24 #include "mojo/public/c/system/message_pipe.h"
25 #include "mojo/public/c/system/types.h"
30 class PlatformSharedBufferMapping;
38 class DispatcherTransport;
40 class LocalMessagePipeEndpoint;
41 class ProxyMessagePipeEndpoint;
45 typedef std::vector<scoped_refptr<Dispatcher>> DispatcherVector;
49 // Test helper. We need to declare it here so we can friend it.
50 MOJO_SYSTEM_IMPL_EXPORT DispatcherTransport
51 DispatcherTryStartTransport(Dispatcher* dispatcher);
55 // A |Dispatcher| implements Mojo primitives that are "attached" to a particular
56 // handle. This includes most (all?) primitives except for |MojoWait...()|. This
57 // object is thread-safe, with its state being protected by a single lock
58 // |lock_|, which is also made available to implementation subclasses (via the
60 class MOJO_SYSTEM_IMPL_EXPORT Dispatcher
61 : public base::RefCountedThreadSafe<Dispatcher> {
66 kTypeDataPipeProducer,
67 kTypeDataPipeConsumer,
70 // "Private" types (not exposed via the public interface):
71 kTypePlatformHandle = -1
73 virtual Type GetType() const = 0;
75 // These methods implement the various primitives named |Mojo...()|. These
76 // take |lock_| and handle races with |Close()|. Then they call out to
77 // subclasses' |...ImplNoLock()| methods (still under |lock_|), which actually
78 // implement the primitives.
79 // NOTE(vtl): This puts a big lock around each dispatcher (i.e., handle), and
80 // prevents the various |...ImplNoLock()|s from releasing the lock as soon as
81 // possible. If this becomes an issue, we can rethink this.
84 // |transports| may be non-null if and only if there are handles to be
85 // written; not that |this| must not be in |transports|. On success, all the
86 // dispatchers in |transports| must have been moved to a closed state; on
87 // failure, they should remain in their original state.
88 MojoResult WriteMessage(UserPointer<const void> bytes,
90 std::vector<DispatcherTransport>* transports,
91 MojoWriteMessageFlags flags);
92 // |dispatchers| must be non-null but empty, if |num_dispatchers| is non-null
93 // and nonzero. On success, it will be set to the dispatchers to be received
94 // (and assigned handles) as part of the message.
95 MojoResult ReadMessage(UserPointer<void> bytes,
96 UserPointer<uint32_t> num_bytes,
97 DispatcherVector* dispatchers,
98 uint32_t* num_dispatchers,
99 MojoReadMessageFlags flags);
100 MojoResult WriteData(UserPointer<const void> elements,
101 UserPointer<uint32_t> elements_num_bytes,
102 MojoWriteDataFlags flags);
103 MojoResult BeginWriteData(UserPointer<void*> buffer,
104 UserPointer<uint32_t> buffer_num_bytes,
105 MojoWriteDataFlags flags);
106 MojoResult EndWriteData(uint32_t num_bytes_written);
107 MojoResult ReadData(UserPointer<void> elements,
108 UserPointer<uint32_t> num_bytes,
109 MojoReadDataFlags flags);
110 MojoResult BeginReadData(UserPointer<const void*> buffer,
111 UserPointer<uint32_t> buffer_num_bytes,
112 MojoReadDataFlags flags);
113 MojoResult EndReadData(uint32_t num_bytes_read);
114 // |options| may be null. |new_dispatcher| must not be null, but
115 // |*new_dispatcher| should be null (and will contain the dispatcher for the
116 // new handle on success).
117 MojoResult DuplicateBufferHandle(
118 UserPointer<const MojoDuplicateBufferHandleOptions> options,
119 scoped_refptr<Dispatcher>* new_dispatcher);
120 MojoResult MapBuffer(
123 MojoMapBufferFlags flags,
124 scoped_ptr<embedder::PlatformSharedBufferMapping>* mapping);
126 // Gets the current handle signals state. (The default implementation simply
127 // returns a default-constructed |HandleSignalsState|, i.e., no signals
128 // satisfied or satisfiable.) Note: The state is subject to change from other
130 HandleSignalsState GetHandleSignalsState() const;
132 // Adds a waiter to this dispatcher. The waiter will be woken up when this
133 // object changes state to satisfy |signals| with context |context|. It will
134 // also be woken up when it becomes impossible for the object to ever satisfy
135 // |signals| with a suitable error status.
137 // If |signals_state| is non-null, on *failure* |*signals_state| will be set
138 // to the current handle signals state (on success, it is left untouched).
141 // - |MOJO_RESULT_OK| if the waiter was added;
142 // - |MOJO_RESULT_ALREADY_EXISTS| if |signals| is already satisfied;
143 // - |MOJO_RESULT_INVALID_ARGUMENT| if the dispatcher has been closed; and
144 // - |MOJO_RESULT_FAILED_PRECONDITION| if it is not (or no longer) possible
145 // that |signals| will ever be satisfied.
146 MojoResult AddWaiter(Waiter* waiter,
147 MojoHandleSignals signals,
149 HandleSignalsState* signals_state);
150 // Removes a waiter from this dispatcher. (It is valid to call this multiple
151 // times for the same |waiter| on the same object, so long as |AddWaiter()|
152 // was called at most once.) If |signals_state| is non-null, |*signals_state|
153 // will be set to the current handle signals state.
154 void RemoveWaiter(Waiter* waiter, HandleSignalsState* signals_state);
156 // A dispatcher must be put into a special state in order to be sent across a
157 // message pipe. Outside of tests, only |HandleTableAccess| is allowed to do
158 // this, since there are requirements on the handle table (see below).
160 // In this special state, only a restricted set of operations is allowed.
161 // These are the ones available as |DispatcherTransport| methods. Other
162 // |Dispatcher| methods must not be called until |DispatcherTransport::End()|
164 class HandleTableAccess {
167 friend class HandleTable;
168 // Tests also need this, to avoid needing |Core|.
169 friend DispatcherTransport test::DispatcherTryStartTransport(Dispatcher*);
171 // This must be called under the handle table lock and only if the handle
172 // table entry is not marked busy. The caller must maintain a reference to
173 // |dispatcher| until |DispatcherTransport::End()| is called.
174 static DispatcherTransport TryStartTransport(Dispatcher* dispatcher);
177 // A |TransportData| may serialize dispatchers that are given to it (and which
178 // were previously attached to the |MessageInTransit| that is creating it) to
179 // a given |Channel| and then (probably in a different process) deserialize.
180 // Note that the |MessageInTransit| "owns" (i.e., has the only ref to) these
181 // dispatchers, so there are no locking issues. (There's no lock ordering
182 // issue, and in fact no need to take dispatcher locks at all.)
183 // TODO(vtl): Consider making another wrapper similar to |DispatcherTransport|
184 // (but with an owning, unique reference), and having
185 // |CreateEquivalentDispatcherAndCloseImplNoLock()| return that wrapper (and
186 // |MessageInTransit|, etc. only holding on to such wrappers).
187 class TransportDataAccess {
189 friend class TransportData;
191 // Serialization API. These functions may only be called on such
192 // dispatchers. (|channel| is the |Channel| to which the dispatcher is to be
193 // serialized.) See the |Dispatcher| methods of the same names for more
195 static void StartSerialize(Dispatcher* dispatcher,
198 size_t* max_platform_handles);
199 static bool EndSerializeAndClose(
200 Dispatcher* dispatcher,
204 embedder::PlatformHandleVector* platform_handles);
206 // Deserialization API.
207 // Note: This "clears" (i.e., reset to the invalid handle) any platform
208 // handles that it takes ownership of.
209 static scoped_refptr<Dispatcher> Deserialize(
214 embedder::PlatformHandleVector* platform_handles);
218 friend class base::RefCountedThreadSafe<Dispatcher>;
221 virtual ~Dispatcher();
223 // These are to be overridden by subclasses (if necessary). They are called
224 // exactly once -- first |CancelAllWaitersNoLock()|, then |CloseImplNoLock()|,
225 // when the dispatcher is being closed. They are called under |lock_|.
226 virtual void CancelAllWaitersNoLock();
227 virtual void CloseImplNoLock();
228 virtual scoped_refptr<Dispatcher>
229 CreateEquivalentDispatcherAndCloseImplNoLock() = 0;
231 // These are to be overridden by subclasses (if necessary). They are never
232 // called after the dispatcher has been closed. They are called under |lock_|.
233 // See the descriptions of the methods without the "ImplNoLock" for more
235 virtual MojoResult WriteMessageImplNoLock(
236 UserPointer<const void> bytes,
238 std::vector<DispatcherTransport>* transports,
239 MojoWriteMessageFlags flags);
240 virtual MojoResult ReadMessageImplNoLock(UserPointer<void> bytes,
241 UserPointer<uint32_t> num_bytes,
242 DispatcherVector* dispatchers,
243 uint32_t* num_dispatchers,
244 MojoReadMessageFlags flags);
245 virtual MojoResult WriteDataImplNoLock(UserPointer<const void> elements,
246 UserPointer<uint32_t> num_bytes,
247 MojoWriteDataFlags flags);
248 virtual MojoResult BeginWriteDataImplNoLock(
249 UserPointer<void*> buffer,
250 UserPointer<uint32_t> buffer_num_bytes,
251 MojoWriteDataFlags flags);
252 virtual MojoResult EndWriteDataImplNoLock(uint32_t num_bytes_written);
253 virtual MojoResult ReadDataImplNoLock(UserPointer<void> elements,
254 UserPointer<uint32_t> num_bytes,
255 MojoReadDataFlags flags);
256 virtual MojoResult BeginReadDataImplNoLock(
257 UserPointer<const void*> buffer,
258 UserPointer<uint32_t> buffer_num_bytes,
259 MojoReadDataFlags flags);
260 virtual MojoResult EndReadDataImplNoLock(uint32_t num_bytes_read);
261 virtual MojoResult DuplicateBufferHandleImplNoLock(
262 UserPointer<const MojoDuplicateBufferHandleOptions> options,
263 scoped_refptr<Dispatcher>* new_dispatcher);
264 virtual MojoResult MapBufferImplNoLock(
267 MojoMapBufferFlags flags,
268 scoped_ptr<embedder::PlatformSharedBufferMapping>* mapping);
269 virtual HandleSignalsState GetHandleSignalsStateImplNoLock() const;
270 virtual MojoResult AddWaiterImplNoLock(Waiter* waiter,
271 MojoHandleSignals signals,
273 HandleSignalsState* signals_state);
274 virtual void RemoveWaiterImplNoLock(Waiter* waiter,
275 HandleSignalsState* signals_state);
277 // These implement the API used to serialize dispatchers to a |Channel|
278 // (described below). They will only be called on a dispatcher that's attached
279 // to and "owned" by a |MessageInTransit|. See the non-"impl" versions for
282 // Note: |StartSerializeImplNoLock()| is actually called with |lock_| NOT
283 // held, since the dispatcher should only be accessible to the calling thread.
284 // On Debug builds, |EndSerializeAndCloseImplNoLock()| is called with |lock_|
285 // held, to satisfy any |lock_.AssertAcquired()| (e.g., in |CloseImplNoLock()|
286 // -- and anything it calls); disentangling those assertions is
287 // difficult/fragile, and would weaken our general checking of invariants.
289 // TODO(vtl): Consider making these pure virtual once most things support
290 // being passed over a message pipe.
291 virtual void StartSerializeImplNoLock(Channel* channel,
293 size_t* max_platform_handles);
294 virtual bool EndSerializeAndCloseImplNoLock(
298 embedder::PlatformHandleVector* platform_handles);
300 // Available to subclasses. (Note: Returns a non-const reference, just like
301 // |base::AutoLock|'s constructor takes a non-const reference.)
302 base::Lock& lock() const { return lock_; }
305 friend class DispatcherTransport;
307 // This should be overridden to return true if/when there's an ongoing
308 // operation (e.g., two-phase read/writes on data pipes) that should prevent a
309 // handle from being sent over a message pipe (with status "busy").
310 virtual bool IsBusyNoLock() const;
312 // Closes the dispatcher. This must be done under lock, and unlike |Close()|,
313 // the dispatcher must not be closed already. (This is the "equivalent" of
314 // |CreateEquivalentDispatcherAndCloseNoLock()|, for situations where the
315 // dispatcher must be disposed of instead of "transferred".)
318 // Creates an equivalent dispatcher -- representing the same resource as this
319 // dispatcher -- and close (i.e., disable) this dispatcher. I.e., this
320 // dispatcher will look as though it was closed, but the resource it
321 // represents will be assigned to the new dispatcher. This must be called
322 // under the dispatcher's lock.
323 scoped_refptr<Dispatcher> CreateEquivalentDispatcherAndCloseNoLock();
325 // API to serialize dispatchers to a |Channel|, exposed to only
326 // |TransportData| (via |TransportData|). They may only be called on a
327 // dispatcher attached to a |MessageInTransit| (and in particular not in
328 // |CoreImpl|'s handle table).
330 // Starts the serialization. Returns (via the two "out" parameters) the
331 // maximum amount of space that may be needed to serialize this dispatcher to
332 // the given |Channel| (no more than
333 // |TransportData::kMaxSerializedDispatcherSize|) and the maximum number of
334 // |PlatformHandle|s that may need to be attached (no more than
335 // |TransportData::kMaxSerializedDispatcherPlatformHandles|). If this
336 // dispatcher cannot be serialized to the given |Channel|, |*max_size| and
337 // |*max_platform_handles| should be set to zero. A call to this method will
338 // ALWAYS be followed by a call to |EndSerializeAndClose()| (even if this
339 // dispatcher cannot be serialized to the given |Channel|).
340 void StartSerialize(Channel* channel,
342 size_t* max_platform_handles);
343 // Completes the serialization of this dispatcher to the given |Channel| and
344 // closes it. (This call will always follow an earlier call to
345 // |StartSerialize()|, with the same |Channel|.) This does so by writing to
346 // |destination| and appending any |PlatformHandle|s needed to
347 // |platform_handles| (which may be null if no platform handles were indicated
348 // to be required to |StartSerialize()|). This may write no more than the
349 // amount indicated by |StartSerialize()|. (WARNING: Beware of races, e.g., if
350 // something can be mutated between the two calls!) Returns true on success,
351 // in which case |*actual_size| is set to the amount it actually wrote to
352 // |destination|. On failure, |*actual_size| should not be modified; however,
353 // the dispatcher will still be closed.
354 bool EndSerializeAndClose(Channel* channel,
357 embedder::PlatformHandleVector* platform_handles);
359 // This protects the following members as well as any state added by
361 mutable base::Lock lock_;
364 DISALLOW_COPY_AND_ASSIGN(Dispatcher);
367 // Wrapper around a |Dispatcher| pointer, while it's being processed to be
368 // passed in a message pipe. See the comment about
369 // |Dispatcher::HandleTableAccess| for more details.
371 // Note: This class is deliberately "thin" -- no more expensive than a
373 class MOJO_SYSTEM_IMPL_EXPORT DispatcherTransport {
375 DispatcherTransport() : dispatcher_(nullptr) {}
379 Dispatcher::Type GetType() const { return dispatcher_->GetType(); }
380 bool IsBusy() const { return dispatcher_->IsBusyNoLock(); }
381 void Close() { dispatcher_->CloseNoLock(); }
382 scoped_refptr<Dispatcher> CreateEquivalentDispatcherAndClose() {
383 return dispatcher_->CreateEquivalentDispatcherAndCloseNoLock();
386 bool is_valid() const { return !!dispatcher_; }
389 Dispatcher* dispatcher() { return dispatcher_; }
392 friend class Dispatcher::HandleTableAccess;
394 explicit DispatcherTransport(Dispatcher* dispatcher)
395 : dispatcher_(dispatcher) {}
397 Dispatcher* dispatcher_;
399 // Copy and assign allowed.
402 } // namespace system
405 #endif // MOJO_EDK_SYSTEM_DISPATCHER_H_