267 lines
8.4 KiB
C++
267 lines
8.4 KiB
C++
// Copyright 2012 Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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// * Neither the name of Google Inc. nor the names of its contributors
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// may be used to endorse or promote products derived from this software
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// without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "utils/signals/interrupts.hpp"
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extern "C" {
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#include <signal.h>
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#include <unistd.h>
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}
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#include <cstdlib>
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#include <cstring>
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#include <set>
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#include "utils/sanity.hpp"
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#include "utils/signals/exceptions.hpp"
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#include "utils/signals/programmer.hpp"
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namespace signals = utils::signals;
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namespace {
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/// The interrupt signal that fired, or -1 if none.
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static volatile int fired_signal = -1;
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/// Collection of PIDs.
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typedef std::set< pid_t > pids_set;
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/// List of processes to kill upon reception of a signal.
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static pids_set pids_to_kill;
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/// Programmer status for the SIGHUP signal.
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static std::auto_ptr< signals::programmer > sighup_handler;
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/// Programmer status for the SIGINT signal.
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static std::auto_ptr< signals::programmer > sigint_handler;
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/// Programmer status for the SIGTERM signal.
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static std::auto_ptr< signals::programmer > sigterm_handler;
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/// Signal mask to restore after exiting a signal inhibited section.
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static sigset_t old_sigmask;
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/// Whether there is an interrupts_handler object in existence or not.
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bool interrupts_handler_active = false;
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/// Whether there is an interrupts_inhibiter object in existence or not.
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bool interrupts_inhibiter_active = false;
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/// Generic handler to capture interrupt signals.
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///
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/// From this handler, we record that an interrupt has happened so that
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/// check_interrupt() can know whether there execution has to be stopped or not.
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/// We also terminate any of our child processes (started by the
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/// utils::process::children class) so that any ongoing wait(2) system calls
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/// terminate.
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///
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/// \param signo The signal that caused this handler to be called.
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static void
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signal_handler(const int signo)
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{
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static const char* message = "[-- Signal caught; please wait for "
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"cleanup --]\n";
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if (::write(STDERR_FILENO, message, std::strlen(message)) == -1) {
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// We are exiting: the message printed here is only for informational
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// purposes. If we fail to print it (which probably means something
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// is really bad), there is not much we can do within the signal
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// handler, so just ignore this.
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}
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fired_signal = signo;
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for (pids_set::const_iterator iter = pids_to_kill.begin();
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iter != pids_to_kill.end(); ++iter) {
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// Redirecting the interrupt signal to our child processes does NOT
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// guarantee that they also terminate. For that to happen, we'd need to
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// SIGKILL them.
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//
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// *However*, because we use this code to invoke the kyua-testers only,
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// and because we assume that such processes are well-behaved and
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// terminate according to our expectations, we do it this way, which
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// allows the testers to know which specific signal made them terminate.
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(void)::kill(*iter, signo);
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}
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}
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/// Installs signal handlers for potential interrupts.
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///
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/// \pre Must not have been called before.
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/// \post The various sig*_handler global variables are atomically updated.
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static void
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setup_handlers(void)
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{
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PRE(sighup_handler.get() == NULL);
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PRE(sigint_handler.get() == NULL);
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PRE(sigterm_handler.get() == NULL);
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// Create the handlers on the stack first so that, if any of them fails, the
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// stack unwinding cleans things up.
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std::auto_ptr< signals::programmer > tmp_sighup_handler(
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new signals::programmer(SIGHUP, signal_handler));
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std::auto_ptr< signals::programmer > tmp_sigint_handler(
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new signals::programmer(SIGINT, signal_handler));
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std::auto_ptr< signals::programmer > tmp_sigterm_handler(
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new signals::programmer(SIGTERM, signal_handler));
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// Now, update the global pointers, which is an operation that cannot fail.
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sighup_handler = tmp_sighup_handler;
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sigint_handler = tmp_sigint_handler;
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sigterm_handler = tmp_sigterm_handler;
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}
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/// Uninstalls the signal handlers installed by setup_handlers().
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static void
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cleanup_handlers(void)
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{
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sighup_handler->unprogram(); sighup_handler.reset(NULL);
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sigint_handler->unprogram(); sigint_handler.reset(NULL);
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sigterm_handler->unprogram(); sigterm_handler.reset(NULL);
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}
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/// Masks the signals installed by setup_handlers().
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static void
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mask_signals(void)
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{
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sigset_t mask;
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sigemptyset(&mask);
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sigaddset(&mask, SIGHUP);
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sigaddset(&mask, SIGINT);
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sigaddset(&mask, SIGTERM);
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#if defined(__minix) && !defined(NDEBUG)
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const int ret =
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#endif /* defined(__minix) && !defined(NDEBUG) */
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::sigprocmask(SIG_BLOCK, &mask, &old_sigmask);
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INV(ret != -1);
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}
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/// Resets the signal masking put in place by mask_signals().
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static void
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unmask_signals(void)
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{
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#if defined(__minix) && !defined(NDEBUG)
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const int ret =
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#endif /* defined(__minix) && !defined(NDEBUG) */
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::sigprocmask(SIG_SETMASK, &old_sigmask, NULL);
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INV(ret != -1);
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}
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} // anonymous namespace
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/// Constructor that sets up the signal handlers.
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signals::interrupts_handler::interrupts_handler(void)
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{
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PRE(!interrupts_handler_active);
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setup_handlers();
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interrupts_handler_active = true;
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}
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/// Destructor that removes the signal handlers.
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signals::interrupts_handler::~interrupts_handler(void)
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{
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cleanup_handlers();
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interrupts_handler_active = false;
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}
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/// Constructor that sets up signal masking.
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signals::interrupts_inhibiter::interrupts_inhibiter(void)
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{
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PRE(!interrupts_inhibiter_active);
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mask_signals();
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interrupts_inhibiter_active = true;
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}
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/// Destructor that removes signal masking.
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signals::interrupts_inhibiter::~interrupts_inhibiter(void)
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{
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unmask_signals();
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interrupts_inhibiter_active = false;
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}
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/// Checks if an interrupt has fired.
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///
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/// Calls to this function should be sprinkled in strategic places through the
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/// code protected by an interrupts_handler object.
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///
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/// \throw interrupted_error If there has been an interrupt.
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void
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signals::check_interrupt(void)
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{
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if (fired_signal != -1)
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throw interrupted_error(fired_signal);
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}
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/// Registers a child process to be killed upon reception of an interrupt.
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///
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/// \pre Must be called with interrupts being inhibited. The caller must ensure
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/// that the call call to fork() and the addition of the PID happen atomically.
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///
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/// \param pid The PID of the child process. Must not have been yet regsitered.
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void
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signals::add_pid_to_kill(const pid_t pid)
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{
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PRE(interrupts_inhibiter_active);
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PRE(pids_to_kill.find(pid) == pids_to_kill.end());
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pids_to_kill.insert(pid);
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}
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/// Unregisters a child process previously registered via add_pid_to_kill().
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///
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/// \pre Must be called with interrupts being inhibited. This is not necessary,
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/// but pushing this to the caller simplifies our logic and provides consistency
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/// with the add_pid_to_kill() call.
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///
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/// \param pid The PID of the child process. Must have been registered
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/// previously, and the process must have already been awaited for.
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void
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signals::remove_pid_to_kill(const pid_t pid)
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{
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PRE(interrupts_inhibiter_active);
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PRE(pids_to_kill.find(pid) != pids_to_kill.end());
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pids_to_kill.erase(pid);
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}
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