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select.c: Introduce support for signalfd 

The signalfd(2) mechanism of Linux allows signals to be delivered
and processed via normal file descriptor I/O.  This avoids any of the
usual problems about re-entrancy of signal processing, as signals can
be processed from the osmocom select() loop abstraction just like any
other event.

Change-Id: If8d89dd1f6989e1cd9b9367fad954d65f91ada30
This commit is contained in:
Harald Welte 2020-04-17 19:20:01 +02:00
parent f3cc731d40
commit a70ac85f5b
3 changed files with 78 additions and 1 deletions
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2
configure.ac
View File

@ -62,7 +62,7 @@ AC_SUBST(LTLDFLAGS_OSMOCTRL)
dnl checks for header files
AC_HEADER_STDC
AC_CHECK_HEADERS(execinfo.h sys/select.h sys/socket.h sys/timerfd.h syslog.h ctype.h netinet/tcp.h netinet/in.h)
AC_CHECK_HEADERS(execinfo.h sys/select.h sys/socket.h sys/signalfd.h sys/timerfd.h syslog.h ctype.h netinet/tcp.h netinet/in.h)
# for src/conv.c
AC_FUNC_ALLOCA
AC_SEARCH_LIBS([dlopen], [dl dld], [LIBRARY_DLOPEN="$LIBS";LIBS=""])

18
include/osmocom/core/select.h
View File

@ -7,6 +7,7 @@
#include <osmocom/core/linuxlist.h>
#include <stdbool.h>
#include <time.h>
#include <signal.h>
/*! \defgroup select Select loop abstraction
* @{
@ -68,4 +69,21 @@ int osmo_timerfd_schedule(struct osmo_fd *ofd, const struct timespec *first,
const struct timespec *interval);
int osmo_timerfd_setup(struct osmo_fd *ofd, int (*cb)(struct osmo_fd *, unsigned int), void *data);
/* signalfd integration */
struct osmo_signalfd;
struct signalfd_siginfo;
typedef void osmo_signalfd_cb(struct osmo_signalfd *osfd, const struct signalfd_siginfo *fdsi);
struct osmo_signalfd {
struct osmo_fd ofd;
sigset_t sigset;
osmo_signalfd_cb *cb;
void *data;
};
struct osmo_signalfd *
osmo_signalfd_setup(void *ctx, sigset_t set, osmo_signalfd_cb *cb, void *data);
/*! @} */

59
src/select.c
View File

@ -392,6 +392,65 @@ int osmo_timerfd_setup(struct osmo_fd *ofd, int (*cb)(struct osmo_fd *, unsigned
#endif /* HAVE_SYS_TIMERFD_H */
#ifdef HAVE_SYS_SIGNALFD_H
#include <sys/signalfd.h>
static int signalfd_callback(struct osmo_fd *ofd, unsigned int what)
{
struct osmo_signalfd *osfd = ofd->data;
struct signalfd_siginfo fdsi;
int rc;
rc = read(ofd->fd, &fdsi, sizeof(fdsi));
if (rc < 0) {
osmo_fd_unregister(ofd);
close(ofd->fd);
ofd->fd = -1;
return rc;
}
osfd->cb(osfd, &fdsi);
return 0;
};
/*! create a signalfd and register it with osmocom select loop.
* \param[in] ctx talloc context from which osmo_signalfd is to be allocated
* \param[in] set of signals to be accept via this file descriptor
* \param[in] cb call-back function to be called for each arriving signal
* \param[in] data opaque user-provided data to pass to callback
* \returns pointer to newly-allocated + registered osmo_signalfd; NULL on error */
struct osmo_signalfd *
osmo_signalfd_setup(void *ctx, sigset_t set, osmo_signalfd_cb *cb, void *data)
{
struct osmo_signalfd *osfd = talloc_size(ctx, sizeof(*osfd));
int fd, rc;
if (!osfd)
return NULL;
osfd->data = data;
osfd->sigset = set;
osfd->cb = cb;
fd = signalfd(-1, &osfd->sigset, SFD_NONBLOCK);
if (fd < 0) {
talloc_free(osfd);
return NULL;
}
osmo_fd_setup(&osfd->ofd, fd, OSMO_FD_READ, signalfd_callback, osfd, 0);
rc = osmo_fd_register(&osfd->ofd);
if (rc < 0) {
close(fd);
talloc_free(osfd);
return NULL;
}
return osfd;
}
#endif /* HAVE_SYS_SIGNALFD_H */
/*! @} */