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| 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. | |
| 4 | |
| 5 #include "mojo/system/waiter.h" | |
| 6 | |
| 7 #include <limits> | |
| 8 | |
| 9 #include "base/logging.h" | |
| 10 #include "base/time/time.h" | |
| 11 | |
| 12 namespace mojo { | |
| 13 namespace system { | |
| 14 | |
| 15 Waiter::Waiter() | |
| 16 : cv_(&lock_), | |
| 17 #ifndef NDEBUG | |
| 18 initialized_(false), | |
| 19 #endif | |
| 20 awoken_(false), | |
| 21 awake_result_(MOJO_RESULT_INTERNAL), | |
| 22 awake_context_(static_cast<uint32_t>(-1)) { | |
| 23 } | |
| 24 | |
| 25 Waiter::~Waiter() { | |
| 26 } | |
| 27 | |
| 28 void Waiter::Init() { | |
| 29 #ifndef NDEBUG | |
| 30 initialized_ = true; | |
| 31 #endif | |
| 32 awoken_ = false; | |
| 33 // NOTE(vtl): If performance ever becomes an issue, we can disable the setting | |
| 34 // of |awake_result_| (except the first one in |Awake()|) in Release builds. | |
| 35 awake_result_ = MOJO_RESULT_INTERNAL; | |
| 36 } | |
| 37 | |
| 38 // TODO(vtl): Fast-path the |deadline == 0| case? | |
| 39 MojoResult Waiter::Wait(MojoDeadline deadline, uint32_t* context) { | |
| 40 base::AutoLock locker(lock_); | |
| 41 | |
| 42 #ifndef NDEBUG | |
| 43 DCHECK(initialized_); | |
| 44 // It'll need to be re-initialized after this. | |
| 45 initialized_ = false; | |
| 46 #endif | |
| 47 | |
| 48 // Fast-path the already-awoken case: | |
| 49 if (awoken_) { | |
| 50 DCHECK_NE(awake_result_, MOJO_RESULT_INTERNAL); | |
| 51 if (context) | |
| 52 *context = awake_context_; | |
| 53 return awake_result_; | |
| 54 } | |
| 55 | |
| 56 // |MojoDeadline| is actually a |uint64_t|, but we need a signed quantity. | |
| 57 // Treat any out-of-range deadline as "forever" (which is wrong, but okay | |
| 58 // since 2^63 microseconds is ~300000 years). Note that this also takes care | |
| 59 // of the |MOJO_DEADLINE_INDEFINITE| (= 2^64 - 1) case. | |
| 60 if (deadline > static_cast<uint64_t>(std::numeric_limits<int64_t>::max())) { | |
| 61 do { | |
| 62 cv_.Wait(); | |
| 63 } while (!awoken_); | |
| 64 } else { | |
| 65 // NOTE(vtl): This is very inefficient on POSIX, since pthreads condition | |
| 66 // variables take an absolute deadline. | |
| 67 const base::TimeTicks end_time = | |
| 68 base::TimeTicks::Now() + | |
| 69 base::TimeDelta::FromMicroseconds(static_cast<int64_t>(deadline)); | |
| 70 do { | |
| 71 base::TimeTicks now_time = base::TimeTicks::Now(); | |
| 72 if (now_time >= end_time) | |
| 73 return MOJO_RESULT_DEADLINE_EXCEEDED; | |
| 74 | |
| 75 cv_.TimedWait(end_time - now_time); | |
| 76 } while (!awoken_); | |
| 77 } | |
| 78 | |
| 79 DCHECK_NE(awake_result_, MOJO_RESULT_INTERNAL); | |
| 80 if (context) | |
| 81 *context = awake_context_; | |
| 82 return awake_result_; | |
| 83 } | |
| 84 | |
| 85 void Waiter::Awake(MojoResult result, uint32_t context) { | |
| 86 base::AutoLock locker(lock_); | |
| 87 | |
| 88 if (awoken_) | |
| 89 return; | |
| 90 | |
| 91 awoken_ = true; | |
| 92 awake_result_ = result; | |
| 93 awake_context_ = context; | |
| 94 cv_.Signal(); | |
| 95 // |cv_.Wait()|/|cv_.TimedWait()| will return after |lock_| is released. | |
| 96 } | |
| 97 | |
| 98 } // namespace system | |
| 99 } // namespace mojo | |
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