external/bsd/kyua-cli/dist/utils/signals/interrupts.cpp

   1 // Copyright 2012 Google Inc.
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  28
  29 #include "utils/signals/interrupts.hpp"
  30
  31 extern "C" {
  32 #include <signal.h>
  33 #include <unistd.h>
  34 }
  35
  36 #include <cstdlib>
  37 #include <cstring>
  38 #include <set>
  39
  40 #include "utils/sanity.hpp"
  41 #include "utils/signals/exceptions.hpp"
  42 #include "utils/signals/programmer.hpp"
  43
  44 namespace signals = utils::signals;
  45
  46
  47 namespace {
  48
  49
  50 /// The interrupt signal that fired, or -1 if none.
  51 static volatile int fired_signal = -1;
  52
  53
  54 /// Collection of PIDs.
  55 typedef std::set< pid_t > pids_set;
  56
  57
  58 /// List of processes to kill upon reception of a signal.
  59 static pids_set pids_to_kill;
  60
  61
  62 /// Programmer status for the SIGHUP signal.
  63 static std::auto_ptr< signals::programmer > sighup_handler;
  64 /// Programmer status for the SIGINT signal.
  65 static std::auto_ptr< signals::programmer > sigint_handler;
  66 /// Programmer status for the SIGTERM signal.
  67 static std::auto_ptr< signals::programmer > sigterm_handler;
  68
  69
  70 /// Signal mask to restore after exiting a signal inhibited section.
  71 static sigset_t old_sigmask;
  72
  73
  74 /// Whether there is an interrupts_handler object in existence or not.
  75 bool interrupts_handler_active = false;
  76
  77
  78 /// Whether there is an interrupts_inhibiter object in existence or not.
  79 bool interrupts_inhibiter_active = false;
  80
  81
  82 /// Generic handler to capture interrupt signals.
  83 ///
  84 /// From this handler, we record that an interrupt has happened so that
  85 /// check_interrupt() can know whether there execution has to be stopped or not.
  86 /// We also terminate any of our child processes (started by the
  87 /// utils::process::children class) so that any ongoing wait(2) system calls
  88 /// terminate.
  89 ///
  90 /// \param signo The signal that caused this handler to be called.
  91 static void
  92 signal_handler(const int signo)
  93 {
  94     static const char* message = "[-- Signal caught; please wait for "
  95         "cleanup --]\n";
  96     if (::write(STDERR_FILENO, message, std::strlen(message)) == -1) {
  97         // We are exiting: the message printed here is only for informational
  98         // purposes.  If we fail to print it (which probably means something
  99         // is really bad), there is not much we can do within the signal
 100         // handler, so just ignore this.
 101     }
 102
 103     fired_signal = signo;
 104
 105     for (pids_set::const_iterator iter = pids_to_kill.begin();
 106         iter != pids_to_kill.end(); ++iter) {
 107         // Redirecting the interrupt signal to our child processes does NOT
 108         // guarantee that they also terminate.  For that to happen, we'd need to
 109         // SIGKILL them.
 110         //
 111         // *However*, because we use this code to invoke the kyua-testers only,
 112         // and because we assume that such processes are well-behaved and
 113         // terminate according to our expectations, we do it this way, which
 114         // allows the testers to know which specific signal made them terminate.
 115         (void)::kill(*iter, signo);
 116     }
 117 }
 118
 119
 120 /// Installs signal handlers for potential interrupts.
 121 ///
 122 /// \pre Must not have been called before.
 123 /// \post The various sig*_handler global variables are atomically updated.
 124 static void
 125 setup_handlers(void)
 126 {
 127     PRE(sighup_handler.get() == NULL);
 128     PRE(sigint_handler.get() == NULL);
 129     PRE(sigterm_handler.get() == NULL);
 130
 131     // Create the handlers on the stack first so that, if any of them fails, the
 132     // stack unwinding cleans things up.
 133     std::auto_ptr< signals::programmer > tmp_sighup_handler(
 134         new signals::programmer(SIGHUP, signal_handler));
 135     std::auto_ptr< signals::programmer > tmp_sigint_handler(
 136         new signals::programmer(SIGINT, signal_handler));
 137     std::auto_ptr< signals::programmer > tmp_sigterm_handler(
 138         new signals::programmer(SIGTERM, signal_handler));
 139
 140     // Now, update the global pointers, which is an operation that cannot fail.
 141     sighup_handler = tmp_sighup_handler;
 142     sigint_handler = tmp_sigint_handler;
 143     sigterm_handler = tmp_sigterm_handler;
 144 }
 145
 146
 147 /// Uninstalls the signal handlers installed by setup_handlers().
 148 static void
 149 cleanup_handlers(void)
 150 {
 151     sighup_handler->unprogram(); sighup_handler.reset(NULL);
 152     sigint_handler->unprogram(); sigint_handler.reset(NULL);
 153     sigterm_handler->unprogram(); sigterm_handler.reset(NULL);
 154 }
 155
 156
 157
 158 /// Masks the signals installed by setup_handlers().
 159 static void
 160 mask_signals(void)
 161 {
 162     sigset_t mask;
 163     sigemptyset(&mask);
 164     sigaddset(&mask, SIGHUP);
 165     sigaddset(&mask, SIGINT);
 166     sigaddset(&mask, SIGTERM);
 167 #if defined(__minix) && !defined(NDEBUG)
 168     const int ret =
 169 #endif /* defined(__minix) && !defined(NDEBUG) */
 170     ::sigprocmask(SIG_BLOCK, &mask, &old_sigmask);
 171     INV(ret != -1);
 172 }
 173
 174
 175 /// Resets the signal masking put in place by mask_signals().
 176 static void
 177 unmask_signals(void)
 178 {
 179 #if defined(__minix) && !defined(NDEBUG)
 180     const int ret =
 181 #endif /* defined(__minix) && !defined(NDEBUG) */
 182     ::sigprocmask(SIG_SETMASK, &old_sigmask, NULL);
 183     INV(ret != -1);
 184 }
 185
 186
 187 }  // anonymous namespace
 188
 189
 190 /// Constructor that sets up the signal handlers.
 191 signals::interrupts_handler::interrupts_handler(void)
 192 {
 193     PRE(!interrupts_handler_active);
 194     setup_handlers();
 195     interrupts_handler_active = true;
 196 }
 197
 198
 199 /// Destructor that removes the signal handlers.
 200 signals::interrupts_handler::~interrupts_handler(void)
 201 {
 202     cleanup_handlers();
 203     interrupts_handler_active = false;
 204 }
 205
 206
 207 /// Constructor that sets up signal masking.
 208 signals::interrupts_inhibiter::interrupts_inhibiter(void)
 209 {
 210     PRE(!interrupts_inhibiter_active);
 211     mask_signals();
 212     interrupts_inhibiter_active = true;
 213 }
 214
 215
 216 /// Destructor that removes signal masking.
 217 signals::interrupts_inhibiter::~interrupts_inhibiter(void)
 218 {
 219     unmask_signals();
 220     interrupts_inhibiter_active = false;
 221 }
 222
 223
 224 /// Checks if an interrupt has fired.
 225 ///
 226 /// Calls to this function should be sprinkled in strategic places through the
 227 /// code protected by an interrupts_handler object.
 228 ///
 229 /// \throw interrupted_error If there has been an interrupt.
 230 void
 231 signals::check_interrupt(void)
 232 {
 233     if (fired_signal != -1)
 234         throw interrupted_error(fired_signal);
 235 }
 236
 237
 238 /// Registers a child process to be killed upon reception of an interrupt.
 239 ///
 240 /// \pre Must be called with interrupts being inhibited.  The caller must ensure
 241 /// that the call call to fork() and the addition of the PID happen atomically.
 242 ///
 243 /// \param pid The PID of the child process.  Must not have been yet regsitered.
 244 void
 245 signals::add_pid_to_kill(const pid_t pid)
 246 {
 247     PRE(interrupts_inhibiter_active);
 248     PRE(pids_to_kill.find(pid) == pids_to_kill.end());
 249     pids_to_kill.insert(pid);
 250 }
 251
 252
 253 /// Unregisters a child process previously registered via add_pid_to_kill().
 254 ///
 255 /// \pre Must be called with interrupts being inhibited.  This is not necessary,
 256 /// but pushing this to the caller simplifies our logic and provides consistency
 257 /// with the add_pid_to_kill() call.
 258 ///
 259 /// \param pid The PID of the child process.  Must have been registered
 260 ///     previously, and the process must have already been awaited for.
 261 void
 262 signals::remove_pid_to_kill(const pid_t pid)
 263 {
 264     PRE(interrupts_inhibiter_active);
 265     PRE(pids_to_kill.find(pid) != pids_to_kill.end());
 266     pids_to_kill.erase(pid);
 267 }