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Use self-pipe instead of signal-blocking for SIGCHLD/SIGWINCH #69

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Use self-pipe instead of signal-blocking for SIGCHLD/SIGWINCH #69

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70 changes: 60 additions & 10 deletions dvtm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,7 @@ typedef struct {
int history;
int w;
int h;
volatile sig_atomic_t need_resize;
bool need_resize;
} Screen;

typedef struct {
Expand Down Expand Up @@ -248,6 +248,10 @@ static const char *shell;
static Register copyreg;
static volatile sig_atomic_t running = true;
static bool runinall = false;
static int sigwinch_pipe[] = {-1, -1};
static int sigchld_pipe[] = {-1, -1};

enum {PIPE_RD, PIPE_WR};

static void
eprint(const char *errstr, ...) {
Expand Down Expand Up @@ -698,6 +702,11 @@ get_client_by_coord(unsigned int x, unsigned int y) {

static void
sigchld_handler(int sig) {
write(sigchld_pipe[PIPE_WR], "\0", 1);
}

static void
handle_sigchld() {
int errsv = errno;
int status;
pid_t pid;
Expand Down Expand Up @@ -731,6 +740,11 @@ sigchld_handler(int sig) {

static void
sigwinch_handler(int sig) {
write(sigwinch_pipe[PIPE_WR], "\0", 1);
}

static void
handle_sigwinch() {
screen.need_resize = true;
}

Expand Down Expand Up @@ -939,6 +953,14 @@ getshell(void) {
return "/bin/sh";
}

static bool
set_blocking(int fd, bool blocking) {
int flags = fcntl(fd, F_GETFL, 0);
if (flags < 0) return false;
flags = blocking ? (flags & ~O_NONBLOCK) : (flags | O_NONBLOCK);
return !fcntl(fd, F_SETFL, flags);
}

static void
setup(void) {
shell = getshell();
Expand All @@ -962,6 +984,23 @@ setup(void) {
colors[i].pair = vt_color_reserve(colors[i].fg, colors[i].bg);
}
resize_screen();

int *pipes[] = {&sigwinch_pipe[0], &sigchld_pipe[0]};
for (int i = 0; i < 2; ++i) {
int r = pipe(pipes[i]);
if (r < 0) {
perror("pipe()");
exit(EXIT_FAILURE);
}

for (int j = 0; j < 2; ++j) {
if (!set_blocking(pipes[i][j], false)) {
perror("fcntl()");
exit(EXIT_FAILURE);
}
}
}

struct sigaction sa;
memset(&sa, 0, sizeof sa);
sa.sa_flags = 0;
Expand Down Expand Up @@ -1815,20 +1854,13 @@ main(int argc, char *argv[]) {
KeyCombo keys;
unsigned int key_index = 0;
memset(keys, 0, sizeof(keys));
sigset_t emptyset, blockset;

setenv("DVTM", VERSION, 1);
if (!parse_args(argc, argv)) {
setup();
startup(NULL);
}

sigemptyset(&emptyset);
sigemptyset(&blockset);
sigaddset(&blockset, SIGWINCH);
sigaddset(&blockset, SIGCHLD);
sigprocmask(SIG_BLOCK, &blockset, NULL);

while (running) {
int r, nfds = 0;
fd_set rd;
Expand All @@ -1841,9 +1873,15 @@ main(int argc, char *argv[]) {
FD_ZERO(&rd);
FD_SET(STDIN_FILENO, &rd);

FD_SET(sigwinch_pipe[PIPE_RD], &rd);
nfds = MAX(nfds, sigwinch_pipe[PIPE_RD]);

FD_SET(sigchld_pipe[PIPE_RD], &rd);
nfds = MAX(nfds, sigchld_pipe[PIPE_RD]);

if (cmdfifo.fd != -1) {
FD_SET(cmdfifo.fd, &rd);
nfds = cmdfifo.fd;
nfds = MAX(nfds, cmdfifo.fd);
}

if (bar.fd != -1) {
Expand All @@ -1867,7 +1905,7 @@ main(int argc, char *argv[]) {
}

doupdate();
r = pselect(nfds + 1, &rd, NULL, NULL, NULL, &emptyset);
r = select(nfds + 1, &rd, NULL, NULL, NULL);

if (r < 0) {
if (errno == EINTR)
Expand Down Expand Up @@ -1903,6 +1941,18 @@ main(int argc, char *argv[]) {
continue;
}

if (FD_ISSET(sigwinch_pipe[PIPE_RD], &rd)) {
char buf[512];
while (read(sigwinch_pipe[PIPE_RD], &buf, sizeof(buf)) > 0);
handle_sigwinch();
}

if (FD_ISSET(sigchld_pipe[PIPE_RD], &rd)) {
char buf[512];
while (read(sigchld_pipe[PIPE_RD], &buf, sizeof(buf)) > 0);
handle_sigchld();
}

if (cmdfifo.fd != -1 && FD_ISSET(cmdfifo.fd, &rd))
handle_cmdfifo();

Expand Down