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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/edk/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 = static_cast<uint32_t>(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 = static_cast<uint32_t>(awake_context_); | |
82 return awake_result_; | |
83 } | |
84 | |
85 bool Waiter::Awake(MojoResult result, uintptr_t context) { | |
86 base::AutoLock locker(lock_); | |
87 | |
88 if (awoken_) | |
89 return true; | |
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 return true; | |
97 } | |
98 | |
99 } // namespace system | |
100 } // namespace mojo | |
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