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Linux: use signalfd rather than a pipe to handle signals

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This commit is contained in:
Kovid Goyal
2019-07-05 14:33:22 +05:30
parent 40186fb54b
commit 547132131a
2 changed files with 57 additions and 10 deletions
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60
kitty/loop-utils.c
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@@ -12,10 +12,14 @@ bool
init_loop_data(LoopData *ld) {
if (!self_pipe(ld->wakeup_fds, true)) return false;
ld->wakeup_read_fd = ld->wakeup_fds[0];
ld->signal_fds[0] = -1; ld->signal_fds[1] = -1; ld->signal_read_fd = -1;
ld->signal_read_fd = -1;
#ifndef HAS_SIGNAL_FD
ld->signal_fds[0] = -1; ld->signal_fds[1] = -1;
#endif
return true;
}
#ifndef HAS_SIGNAL_FD
static int signal_write_fd = -1;
static void
@@ -29,16 +33,30 @@ handle_signal(int sig_num) {
}
errno = save_err;
}
#endif
#define SIGNAL_SET \
sigset_t signals = {0}; \
sigemptyset(&signals); \
sigaddset(&signals, SIGINT); sigaddset(&signals, SIGTERM); sigaddset(&signals, SIGCHLD); \
void
free_loop_data(LoopData *ld) {
#define CLOSE(which, idx) if (ld->which[idx] > -1) close(ld->which[idx]); ld->which[idx] = -1;
CLOSE(wakeup_fds, 0); CLOSE(wakeup_fds, 1);
#ifndef HAS_SIGNAL_FD
CLOSE(signal_fds, 0); CLOSE(signal_fds, 1);
#endif
#undef CLOSE
if (ld->signal_read_fd) {
#ifdef HAS_SIGNAL_FD
close(ld->signal_read_fd);
SIGNAL_SET
sigprocmask(SIG_UNBLOCK, &signals, NULL);
#else
signal_write_fd = -1;
#endif
signal(SIGINT, SIG_DFL);
signal(SIGTERM, SIG_DFL);
signal(SIGCHLD, SIG_DFL);
@@ -60,9 +78,14 @@ wakeup_loop(LoopData *ld, bool in_signal_handler) {
}
bool
install_signal_handlers(LoopData *ld) {
#ifdef HAS_SIGNAL_FD
SIGNAL_SET
if (sigprocmask(SIG_BLOCK, &signals, NULL) == -1) return false;
ld->signal_read_fd = signalfd(-1, &signals, SFD_NONBLOCK | SFD_CLOEXEC);
if (ld->signal_read_fd == -1) return false;
#else
if (!self_pipe(ld->signal_fds, true)) return false;
signal_write_fd = ld->signal_fds[1];
struct sigaction act = {.sa_handler=handle_signal};
@@ -70,25 +93,42 @@ install_signal_handlers(LoopData *ld) {
SA(SIGINT); SA(SIGTERM); SA(SIGCHLD);
#undef SA
ld->signal_read_fd = ld->signal_fds[0];
#endif
return true;
}
static inline void
read_signals_from_pipe_fd(int fd, handle_signal_func callback, void *data) {
void
read_signals(int fd, handle_signal_func callback, void *data) {
#ifdef HAS_SIGNAL_FD
static struct signalfd_siginfo fdsi[32];
while (true) {
ssize_t s = read(fd, &fdsi, sizeof(fdsi));
if (s < 0) {
if (errno == EINTR) continue;
if (errno == EAGAIN) break;
log_error("Call to read() from read_signals() failed with error: %s", strerror(errno));
break;
}
if (s == 0) break;
size_t num_signals = s / sizeof(struct signalfd_siginfo);
if (num_signals == 0 || num_signals * sizeof(struct signalfd_siginfo) != (size_t)s) {
log_error("Incomplete signal read from signalfd");
break;
}
for (size_t i = 0; i < num_signals; i++) callback(fdsi[i].ssi_signo, data);
}
#else
static char buf[256];
while(true) {
ssize_t len = read(fd, buf, sizeof(buf));
if (len < 0) {
if (errno == EINTR) continue;
if (errno != EIO && errno != EAGAIN) log_error("Call to read() from read_signals_from_pipe_fd() failed with error: %s", strerror(errno));
if (errno != EIO && errno != EAGAIN) log_error("Call to read() from read_signals() failed with error: %s", strerror(errno));
break;
}
for (ssize_t i = 0; i < len; i++) callback(buf[i], data);
if (len == 0) break;
}
}
void
read_signals(int fd, handle_signal_func callback, void *data) {
read_signals_from_pipe_fd(fd, callback, data);
#endif
}

7
kitty/loop-utils.h
View File

@@ -10,9 +10,16 @@
#include <fcntl.h>
#include <unistd.h>
#if __has_include(<sys/signalfd.h>)
#define HAS_SIGNAL_FD
#include <sys/signalfd.h>
#endif
typedef struct {
int wakeup_fds[2];
#ifndef HAS_SIGNAL_FD
int signal_fds[2];
#endif
int wakeup_read_fd;
int signal_read_fd;
} LoopData;