Signal handling.

runtime/bin/process_linux.cc

Index: runtime/bin/process_linux.cc
diff --git a/runtime/bin/process_linux.cc b/runtime/bin/process_linux.cc
index 95d11cdce7dc2b8ee6a2aaf0ce1bcf12900d69de..02546987011b491e9329b9af650741706957146a 100644
--- a/runtime/bin/process_linux.cc
+++ b/runtime/bin/process_linux.cc
@@ -18,6 +18,7 @@
 
 #include "bin/fdutils.h"
 #include "bin/log.h"
+#include "bin/signal_blocker.h"
 #include "bin/thread.h"
 
 
@@ -630,6 +631,116 @@ intptr_t Process::CurrentProcessId() {
   return static_cast<intptr_t>(getpid());
 }
 
+
+static Mutex* signal_mutex = new Mutex();
+static const int kSignalsCount = 3;
+static const int kSignals[kSignalsCount] = {
+  SIGINT,
+  SIGWINCH,
+  SIGTERM

[Søren Gjesse, 2013/12/18 08:07:14]

Shouldn't the SIGUSR1 and SIGUSR2 be in this list as well?

[Anders Johnsen, 2013/12/18 21:20:29]

Done.

+};
+
+
+class SignalInfo {
+ public:
+  SignalInfo(int fd, SignalInfo* prev = NULL)
+      : fd_(fd), port_(Dart_GetMainPortId()), next_(NULL), prev_(prev) {
+    if (prev_ != NULL) {
+      prev_->next_ = this;
+    }
+  }
+
+  void Unlink() {
+    if (prev_ != NULL) {
+      prev_->next_ = next_;
+    }
+    if (next_ != NULL) {
+      next_->prev_ = prev_;
+    }
+  }
+
+  int fd() const { return fd_; }
+  Dart_Port port() const { return port_; }
+  SignalInfo* next() const { return next_; }
+
+ private:
+  int fd_;
+  Dart_Port port_;
+  SignalInfo* next_;
+  SignalInfo* prev_;
+};
+
+
+static SignalInfo* signal_handlers[32] = { NULL };

[Søren Gjesse, 2013/12/18 08:07:14]

Wouldn't it be OK to have the signal in the SignalInfo class, and just go
through all of them for all signals?

Otherwise add a constant kMaxSignal and check on that when adding.

[Anders Johnsen, 2013/12/18 21:20:29]

Done.

+
+
+static void SignalHandler(int signal) {
+  MutexLocker lock(signal_mutex);
+  const SignalInfo* handler = signal_handlers[signal];
+  while (handler != NULL) {
+    int value = 0;

[Søren Gjesse, 2013/12/18 08:07:14]

Can we loose a signal here if the non-blocking write returns 0. Maybe the pipe
is full as for some reason the eventhandler is not fast enough to read from the
pipe. Probably very unlikely.

[Anders Johnsen, 2013/12/18 21:20:29]

This write is blocking.

+    VOID_TEMP_FAILURE_RETRY(write(handler->fd(), &value, 1));
+    handler = handler->next();
+  }
+}
+
+
+intptr_t Process::SetSignalHandler(intptr_t signal) {

[Søren Gjesse, 2013/12/18 08:07:14]

Check that the signal is actually in the kSignals array.

[Anders Johnsen, 2013/12/18 21:20:29]

Done.

+  int fds[2];
+  if (TEMP_FAILURE_RETRY_BLOCK_SIGNALS(pipe(fds)) != 0) {
+    return -1;
+  }
+  if (!FDUtils::SetNonBlocking(fds[0])) {
+    VOID_TEMP_FAILURE_RETRY_BLOCK_SIGNALS(close(fds[0]));
+    VOID_TEMP_FAILURE_RETRY_BLOCK_SIGNALS(close(fds[1]));
+    return -1;
+  }
+  ThreadSignalBlocker blocker(kSignalsCount, kSignals);
+  MutexLocker lock(signal_mutex);
+  if (signal_handlers[signal] == NULL) {
+    struct sigaction act;
+    bzero(&act, sizeof(act));
+    act.sa_handler = SignalHandler;
+    int status = TEMP_FAILURE_RETRY_BLOCK_SIGNALS(
+        sigaction(signal, &act, NULL));
+    if (status < 0) {
+      VOID_TEMP_FAILURE_RETRY_BLOCK_SIGNALS(close(fds[0]));
+      VOID_TEMP_FAILURE_RETRY_BLOCK_SIGNALS(close(fds[1]));
+      return -1;
+    }
+    SignalInfo* info = new SignalInfo(fds[1]);
+    signal_handlers[signal] = info;
+  } else {
+    new SignalInfo(fds[1], signal_handlers[signal]);
+  }
+  return fds[0];
+}
+
+
+void Process::ClearSignalHandler(intptr_t signal) {
+  ThreadSignalBlocker blocker(kSignalsCount, kSignals);
+  MutexLocker lock(signal_mutex);
+  SignalInfo * handler = signal_handlers[signal];
+  while (handler != NULL) {

[Søren Gjesse, 2013/12/18 08:07:14]

Why this loop? Seems that port is always equals to Dart_GetMainPortId(), and if
not this is an infinite loop.

[Anders Johnsen, 2013/12/18 21:20:29]

This is a way to map it to different isolates. We should only remove for the
right isolate. But there was a bug, now fixed.

+    if (handler->port() == Dart_GetMainPortId()) {
+      handler->Unlink();
+      break;
+    }
+  }
+  if (handler != NULL) {
+    if (signal_handlers[signal] == handler) {
+      signal_handlers[signal] = handler->next();
+    }
+    if (signal_handlers[signal] == NULL) {
+      struct sigaction act;
+      bzero(&act, sizeof(act));
+      act.sa_handler = SIG_DFL;
+      VOID_TEMP_FAILURE_RETRY_BLOCK_SIGNALS(sigaction(signal, &act, NULL));
+    }
+  }
+  delete handler;
+}
+
 }  // namespace bin
 }  // namespace dart