4 // Fraunhofer Institute for Open Communication Systems (FOKUS)
5 // Competence Center NETwork research (NET), St. Augustin, GERMANY
6 // Stefan Bund <g0dil@berlios.de>
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 2 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the
20 // Free Software Foundation, Inc.,
21 // 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
24 \brief FIFORunner non-inline non-template implementation */
26 #include "FIFORunner.hh"
27 //#include "FIFORunner.ih"
32 #include "../Utils/Exception.hh"
33 #include "../Utils/senfassert.hh"
35 //#include "FIFORunner.mpp"
37 ///////////////////////////////cc.p////////////////////////////////////////
39 prefix_ senf::scheduler::detail::FIFORunner::FIFORunner()
40 : tasks_ (), next_ (tasks_.end()), watchdogMs_ (1000), watchdogCount_(0), hangCount_ (0)
43 ::memset(&ev, 0, sizeof(ev));
44 ev.sigev_notify = SIGEV_SIGNAL;
45 ev.sigev_signo = SIGURG;
46 ev.sigev_value.sival_ptr = this;
47 if (timer_create(CLOCK_MONOTONIC, &ev, &watchdogId_) < 0)
48 SENF_THROW_SYSTEM_EXCEPTION("timer_create()");
51 ::memset(&sa, 0, sizeof(sa));
52 sa.sa_sigaction = &watchdog;
53 sa.sa_flags = SA_SIGINFO;
54 if (sigaction(SIGURG, &sa, 0) < 0)
55 SENF_THROW_SYSTEM_EXCEPTION("sigaction()");
59 sigaddset(&mask, SIGURG);
60 if (sigprocmask(SIG_UNBLOCK, &mask, 0) < 0)
61 SENF_THROW_SYSTEM_EXCEPTION("sigprocmask()");
64 prefix_ senf::scheduler::detail::FIFORunner::~FIFORunner()
66 timer_delete(watchdogId_);
67 signal(SIGURG, SIG_DFL);
70 // At the moment, the FIFORunner is not very efficient with many non-runnable tasks since the
71 // complete list of tasks is traversed on each run().
73 // To optimize this, we woould need a way to find the relative ordering of two tasks in O(1) (at the
74 // moment, this is an O(N) operation by traversing the list).
76 // One idea is, to give each task an 'order' value. Whenever a task is added at the end, it's order
77 // value is set to the order value of the last task + 1. Whenever the order value such added exceeds
78 // some threshold (e.g. 2^31 -1 or some such), the task list is traversed from beginning to end to
79 // assign new consecutive order values. This O(N) operation is so seldom, that it is amortized over
82 // With this value at hand, we can do several optimizations: One idea would be the following: The
83 // runnable set always has two types of tasks: There are tasks, which are heavily active and are
84 // signaled constantly and other tasks which lie dormant most of the time. Those dormant tasks will
85 // end up at the beginning of the task queue.
87 // With the above defined 'ordering' field available, we can manage an iterator pointing to the
88 // first and the last runnable task. This will often help a lot since the group of runnable tasks
89 // will mostly be localized to the end of the queue. only occasionally one of the dormant tasks will
90 // be runnable. This additional traversal time will be amortized over a larger time.
92 prefix_ void senf::scheduler::detail::FIFORunner::dequeue(TaskInfo * task)
94 TaskList::iterator i (TaskList::current(*task));
102 : public senf::scheduler::detail::FIFORunner::TaskInfo
104 NullTask() : senf::scheduler::detail::FIFORunner::TaskInfo ("<null>") {}
109 prefix_ void senf::scheduler::detail::FIFORunner::run()
111 // This algorithm is carefully adjusted to make it work even when arbitrary tasks are removed
113 // - Before we begin, we add a NullTask to the queue. The only purpose of this node is, to mark
114 // the current end of the queue. The iterator to this node becomes the end iterator of the
116 // - We update the TaskInfo and move it to the end of the queue before calling the callback so
117 // we don't access the TaskInfo if it is removed while the callback is running
118 // - We keep the next to-be-processed node in a class variable which is checked and updated
119 // whenever a node is removed.
121 struct itimerspec timer;
122 timer.it_interval.tv_sec = watchdogMs_ / 1000;
123 timer.it_interval.tv_nsec = (watchdogMs_ % 1000) * 1000000ul;
124 timer.it_value.tv_sec = timer.it_interval.tv_sec;
125 timer.it_value.tv_nsec = timer.it_interval.tv_nsec;
126 tasks_.push_back(null);
127 TaskList::iterator end (TaskList::current(null));
128 next_ = tasks_.begin();
130 if (timer_settime(watchdogId_, 0, &timer, 0) < 0)
131 SENF_THROW_SYSTEM_EXCEPTION("timer_settime()");
132 while (next_ != end) {
133 TaskInfo & task (*next_);
134 if (task.runnable_) {
135 task.runnable_ = false;
136 runningName_ = task.name_;
138 runningBacktrace_ = task.backtrace_;
140 TaskList::iterator i (next_);
142 tasks_.splice(tasks_.end(), tasks_, i);
152 timer.it_interval.tv_sec = 0;
153 timer.it_interval.tv_nsec = 0;
154 timer.it_value.tv_sec = 0;
155 timer.it_value.tv_nsec = 0;
156 timer_settime(watchdogId_, 0, &timer, 0);
158 next_ = tasks_.end();
162 timer.it_interval.tv_sec = 0;
163 timer.it_interval.tv_nsec = 0;
164 timer.it_value.tv_sec = 0;
165 timer.it_value.tv_nsec = 0;
166 if (timer_settime(watchdogId_, 0, &timer, 0) < 0)
167 SENF_THROW_SYSTEM_EXCEPTION("timer_settime()");
169 next_ = tasks_.end();
172 prefix_ void senf::scheduler::detail::FIFORunner::watchdog(int, siginfo_t * si, void *)
174 FIFORunner & runner (*static_cast<FIFORunner *>(si->si_value.sival_ptr));
175 if (runner.watchdogCount_ > 0) {
176 ++ runner.watchdogCount_;
177 if (runner.watchdogCount_ > 2) {
178 ++ runner.hangCount_;
179 write(1, "\n\n*** Scheduler task hanging: ", 30);
180 write(1, runner.runningName_.c_str(), runner.runningName_.size());
183 write(1, "Task was initialized at\n", 24);
184 write(1, runner.runningBacktrace_.c_str(), runner.runningBacktrace_.size());
191 ///////////////////////////////cc.e////////////////////////////////////////
193 //#include "FIFORunner.mpp"
199 // comment-column: 40
200 // c-file-style: "senf"
201 // indent-tabs-mode: nil
202 // ispell-local-dictionary: "american"
203 // compile-command: "scons -u test"