1 # Copyright (c) 2010 Nicira, Inc.
3 # Licensed under the Apache License, Version 2.0 (the "License");
4 # you may not use this file except in compliance with the License.
5 # You may obtain a copy of the License at:
7 # http://www.apache.org/licenses/LICENSE-2.0
9 # Unless required by applicable law or agreed to in writing, software
10 # distributed under the License is distributed on an "AS IS" BASIS,
11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 # See the License for the specific language governing permissions and
13 # limitations under the License.
21 vlog = ovs.vlog.Vlog("poller")
29 # eventlet/gevent doesn't support select.poll. If select.poll is used,
30 # python interpreter is blocked as a whole instead of switching from the
31 # current thread that is about to block to other runnable thread.
32 # So emulate select.poll by select.select because using python means that
33 # performance isn't so important.
34 class _SelectSelect(object):
35 """ select.poll emulation by using select.select.
36 Only register and poll are needed at the moment.
43 def register(self, fd, events):
44 if isinstance(fd, socket.socket):
46 assert isinstance(fd, int)
56 def poll(self, timeout):
58 # epoll uses -1 for infinite timeout, select uses None.
61 timeout = float(timeout) / 1000
63 rlist, wlist, xlist = select.select(self.rlist, self.wlist, self.xlist,
65 # collections.defaultdict is introduced by python 2.5 and
66 # XenServer uses python 2.4. We don't use it for XenServer.
67 # events_dict = collections.defaultdict(int)
68 # events_dict[fd] |= event
71 events_dict[fd] = events_dict.get(fd, 0) | POLLIN
73 events_dict[fd] = events_dict.get(fd, 0) | POLLOUT
75 events_dict[fd] = events_dict.get(fd, 0) | (POLLERR |
78 return events_dict.items()
81 SelectPoll = _SelectSelect
82 # If eventlet/gevent isn't used, we can use select.poll by replacing
83 # _SelectPoll with select.poll class
84 # _SelectPoll = select.poll
88 """High-level wrapper around the "poll" system call.
90 Intended usage is for the program's main loop to go about its business
91 servicing whatever events it needs to. Then, when it runs out of immediate
92 tasks, it calls each subordinate module or object's "wait" function, which
93 in turn calls one (or more) of the functions Poller.fd_wait(),
94 Poller.immediate_wake(), and Poller.timer_wait() to register to be awakened
95 when the appropriate event occurs. Then the main loop calls
96 Poller.block(), which blocks until one of the registered events happens."""
101 def fd_wait(self, fd, events):
102 """Registers 'fd' as waiting for the specified 'events' (which should
103 be select.POLLIN or select.POLLOUT or their bitwise-OR). The following
104 call to self.block() will wake up when 'fd' becomes ready for one or
105 more of the requested events.
107 The event registration is one-shot: only the following call to
108 self.block() is affected. The event will need to be re-registered
109 after self.block() is called if it is to persist.
111 'fd' may be an integer file descriptor or an object with a fileno()
112 method that returns an integer file descriptor."""
113 self.poll.register(fd, events)
115 def __timer_wait(self, msec):
116 if self.timeout < 0 or msec < self.timeout:
119 def timer_wait(self, msec):
120 """Causes the following call to self.block() to block for no more than
121 'msec' milliseconds. If 'msec' is nonpositive, the following call to
122 self.block() will not block at all.
124 The timer registration is one-shot: only the following call to
125 self.block() is affected. The timer will need to be re-registered
126 after self.block() is called if it is to persist."""
128 self.immediate_wake()
130 self.__timer_wait(msec)
132 def timer_wait_until(self, msec):
133 """Causes the following call to self.block() to wake up when the
134 current time, as returned by ovs.timeval.msec(), reaches 'msec' or
135 later. If 'msec' is earlier than the current time, the following call
136 to self.block() will not block at all.
138 The timer registration is one-shot: only the following call to
139 self.block() is affected. The timer will need to be re-registered
140 after self.block() is called if it is to persist."""
141 now = ovs.timeval.msec()
143 self.immediate_wake()
145 self.__timer_wait(msec - now)
147 def immediate_wake(self):
148 """Causes the following call to self.block() to wake up immediately,
153 """Blocks until one or more of the events registered with
154 self.fd_wait() occurs, or until the minimum duration registered with
155 self.timer_wait() elapses, or not at all if self.immediate_wake() has
159 events = self.poll.poll(self.timeout)
160 self.__log_wakeup(events)
161 except select.error, e:
164 if error != errno.EINTR:
165 vlog.err("poll: %s" % e[1])
169 def __log_wakeup(self, events):
171 vlog.dbg("%d-ms timeout" % self.timeout)
173 for fd, revents in events:
178 if revents & POLLOUT:
180 if revents & POLLERR:
182 if revents & POLLHUP:
184 if revents & POLLNVAL:
186 vlog.dbg("%s on fd %d" % (s, fd))
189 self.poll = SelectPoll()