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Problem: eventfd leaks socket on fork+exec

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Solution: if available, use eventfd with EFD_CLOEXEC flag to make
the process close the socket on fork+exec
This commit is contained in:
Luca Boccassi 2016-12-26 18:18:00 +01:00
parent 211898d243
commit f287c7a2aa
6 changed files with 58 additions and 3 deletions
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3
CMakeLists.txt
View File

@ -183,6 +183,9 @@ check_include_files (ifaddrs.h ZMQ_HAVE_IFADDRS)
check_include_files (windows.h ZMQ_HAVE_WINDOWS)
check_include_files (sys/uio.h ZMQ_HAVE_UIO)
check_include_files (sys/eventfd.h ZMQ_HAVE_EVENTFD)
if (ZMQ_HAVE_EVENTFD)
zmq_check_efd_cloexec ()
endif ()
check_library_exists (ws2_32 fopen "" HAVE_WS2_32) # TODO: Why doesn't something logical like WSAStartup work?
check_library_exists (ws2 fopen "" HAVE_WS2)

23
acinclude.m4
View File

@ -614,6 +614,29 @@ int main (int argc, char *argv [])
AS_IF([test "x$libzmq_cv_sock_cloexec" = "xyes"], [$1], [$2])
}])
dnl ################################################################################
dnl # LIBZMQ_CHECK_EVENTFD_CLOEXEC([action-if-found], [action-if-not-found]) #
dnl # Check if EFD_CLOEXEC is supported #
dnl ################################################################################
AC_DEFUN([LIBZMQ_CHECK_EVENTFD_CLOEXEC], [{
AC_CACHE_CHECK([whether EFD_CLOEXEC is supported], [libzmq_cv_efd_cloexec],
[AC_TRY_RUN([/* EFD_CLOEXEC test */
#include <sys/eventfd.h>
int main (int argc, char *argv [])
{
int s = eventfd (0, EFD_CLOEXEC);
return (s == -1);
}
],
[libzmq_cv_efd_cloexec="yes"],
[libzmq_cv_efd_cloexec="no"],
[libzmq_cv_efd_cloexec="not during cross-compile"]
)]
)
AS_IF([test "x$libzmq_cv_efd_cloexec" = "xyes"], [$1], [$2])
}])
dnl ################################################################################
dnl # LIBZMQ_CHECK_ATOMIC_INSTRINSICS([action-if-found], [action-if-not-found]) #
dnl # Check if compiler supoorts __atomic_Xxx intrinsics #

15
builds/cmake/Modules/ZMQSourceRunChecks.cmake
View File

@ -16,6 +16,21 @@ int main(int argc, char *argv [])
ZMQ_HAVE_SOCK_CLOEXEC)
endmacro()
macro(zmq_check_efd_cloexec)
message(STATUS "Checking whether EFD_CLOEXEC is supported")
check_c_source_runs(
"
#include <sys/eventfd.h>
int main(int argc, char *argv [])
{
int s = eventfd (0, EFD_CLOEXEC);
return(s == -1);
}
"
ZMQ_HAVE_EVENTFD_CLOEXEC)
endmacro()
# TCP keep-alives Checks.
macro(zmq_check_so_keepalive)

1
builds/cmake/platform.hpp.in
View File

@ -17,6 +17,7 @@
#cmakedefine ZMQ_HAVE_UIO
#cmakedefine ZMQ_HAVE_EVENTFD
#cmakedefine ZMQ_HAVE_EVENTFD_CLOEXEC
#cmakedefine ZMQ_HAVE_IFADDRS
#cmakedefine ZMQ_HAVE_SO_PEERCRED

10
configure.ac
View File

@ -358,8 +358,14 @@ AC_ARG_ENABLE([eventfd],
if test "x$zmq_enable_eventfd" = "xyes"; then
# Check if we have eventfd.h header file.
AC_CHECK_HEADERS(sys/eventfd.h,
[AC_DEFINE(ZMQ_HAVE_EVENTFD, 1, [Have eventfd extension])])
AC_CHECK_HEADERS(sys/eventfd.h, [
AC_DEFINE(ZMQ_HAVE_EVENTFD, 1, [Have eventfd extension])
LIBZMQ_CHECK_EVENTFD_CLOEXEC([
AC_DEFINE([ZMQ_HAVE_EVENTFD_CLOEXEC],
[1],
[Whether EFD_CLOEXEC is defined and functioning.])
])
])
fi
# Conditionally build performance measurement tools

9
src/signaler.cpp
View File

@ -381,7 +381,14 @@ void zmq::signaler_t::forked ()
int zmq::signaler_t::make_fdpair (fd_t *r_, fd_t *w_)
{
#if defined ZMQ_HAVE_EVENTFD
fd_t fd = eventfd (0, 0);
int flags = 0;
#if defined ZMQ_HAVE_EVENTFD_CLOEXEC
// Setting this option result in sane behaviour when exec() functions
// are used. Old sockets are closed and don't block TCP ports, avoid
// leaks, etc.
flags |= EFD_CLOEXEC;
#endif
fd_t fd = eventfd (0, flags);
if (fd == -1) {
errno_assert (errno == ENFILE || errno == EMFILE);
*w_ = *r_ = -1;