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create signaler::recv_failable()

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In real world usage, there have been reported signaler failures where the
eventfd read() or socket recv() system call in signaler::recv() fails,
despite having made a prior successful signaler::wait() call.

this patch creates a signaler::recv_failable() method that allows
unreadable eventfd / socket to return an error without asserting.
This commit is contained in:
KIU Shueng Chuan
2015-09-29 09:14:02 +08:00
parent 52ee724144
commit 596d6e5b1c
3 changed files with 69 additions and 17 deletions
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77
src/signaler.cpp
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@@ -289,23 +289,18 @@ void zmq::signaler_t::recv ()
#if defined ZMQ_HAVE_EVENTFD
uint64_t dummy;
ssize_t sz = read (r, &dummy, sizeof (dummy));
if (sz == -1) {
errno_assert (errno == EAGAIN);
}
else {
errno_assert (sz == sizeof (dummy));
errno_assert (sz == sizeof (dummy));
// If we accidentally grabbed the next signal(s) along with the current
// one, return it back to the eventfd object.
if (unlikely (dummy > 1)) {
const uint64_t inc = dummy - 1;
ssize_t sz2 = write (w, &inc, sizeof (inc));
errno_assert (sz2 == sizeof (inc));
return;
}
zmq_assert (dummy == 1);
// If we accidentally grabbed the next signal(s) along with the current
// one, return it back to the eventfd object.
if (unlikely (dummy > 1)) {
const uint64_t inc = dummy - 1;
ssize_t sz2 = write (w, &inc, sizeof (inc));
errno_assert (sz2 == sizeof (inc));
return;
}
zmq_assert (dummy == 1);
#else
unsigned char dummy;
#if defined ZMQ_HAVE_WINDOWS
@@ -320,6 +315,58 @@ void zmq::signaler_t::recv ()
#endif
}
int zmq::signaler_t::recv_failable ()
{
// Attempt to read a signal.
#if defined ZMQ_HAVE_EVENTFD
uint64_t dummy;
ssize_t sz = read (r, &dummy, sizeof (dummy));
if (sz == -1) {
errno_assert (errno == EAGAIN);
return -1;
}
else {
errno_assert (sz == sizeof (dummy));
// If we accidentally grabbed the next signal(s) along with the current
// one, return it back to the eventfd object.
if (unlikely (dummy > 1)) {
const uint64_t inc = dummy - 1;
ssize_t sz2 = write (w, &inc, sizeof (inc));
errno_assert (sz2 == sizeof (inc));
return 0;
}
zmq_assert (dummy == 1);
}
#else
unsigned char dummy;
#if defined ZMQ_HAVE_WINDOWS
int nbytes = ::recv (r, (char*) &dummy, sizeof (dummy), 0);
if (nbytes == SOCKET_ERROR) {
const int last_error = WSAGetLastError();
if (last_error == WSAEWOULDBLOCK) {
errno = EAGAIN;
return -1;
}
wsa_assert (last_error == WSAEWOULDBLOCK);
}
#else
ssize_t nbytes = ::recv (r, &dummy, sizeof (dummy), 0);
if (nbytes == -1) {
if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) {
errno = EAGAIN;
return -1;
}
errno_assert (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR);
}
#endif
zmq_assert (nbytes == sizeof (dummy));
zmq_assert (dummy == 0);
#endif
return 0;
}
#ifdef HAVE_FORK
void zmq::signaler_t::forked ()
{