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fix: use poll with self-pipe instead of pselect for fds >= 1024 #26

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Merged
markparonyan merged 1 commit into from
Oct 1, 2026
Merged

fix: use poll with self-pipe instead of pselect for fds >= 1024 #26

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95 changes: 64 additions & 31 deletions dvtm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@
#include <wchar.h>
#include <limits.h>
#include <libgen.h>
#include <sys/select.h>
#include <poll.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
Expand Down Expand Up @@ -82,6 +82,7 @@ struct Client {
Client *prev;
Client *snext;
unsigned int tags;
int pollidx;
};

typedef struct {
Expand Down Expand Up @@ -246,6 +247,7 @@ static CmdFifo cmdfifo = { .fd = -1 };
static const char *shell;
static Register copyreg;
static volatile sig_atomic_t running = true;
static int sigpipe[2] = { -1, -1 };
static bool runinall = false;

static void
Expand Down Expand Up @@ -705,6 +707,16 @@ get_client_by_coord(unsigned int x, unsigned int y) {
return NULL;
}

static void
sigwake(void) {
int errsv = errno;
char b = 0;
ssize_t r = write(sigpipe[1], &b, 1);

(void)r;
errno = errsv;
}

static void
sigchld_handler(int sig) {
int errsv = errno;
Expand Down Expand Up @@ -736,16 +748,36 @@ sigchld_handler(int sig) {
}

errno = errsv;
sigwake();
}

static void
sigwinch_handler(int sig) {
screen.need_resize = true;
sigwake();
}

static void
sigterm_handler(int sig) {
running = false;
sigwake();
}

static void
sigpipe_init(void) {
if (pipe(sigpipe) == -1)
eprint("pipe: %s\n", strerror(errno));
for (int i = 0; i < 2; i++) {
fcntl(sigpipe[i], F_SETFD, FD_CLOEXEC);
fcntl(sigpipe[i], F_SETFL, fcntl(sigpipe[i], F_GETFL) | O_NONBLOCK);
}
}

static void
sigpipe_drain(void) {
char buf[64];

while (read(sigpipe[0], buf, sizeof buf) > 0);
}

static void
Expand Down Expand Up @@ -965,10 +997,8 @@ querycolors(void) {
size_t len = 0;
if (write(STDOUT_FILENO, query, sizeof query - 1) == sizeof query - 1) {
for (;;) {
fd_set rd;
FD_ZERO(&rd);
FD_SET(STDIN_FILENO, &rd);
if (select(STDIN_FILENO + 1, &rd, NULL, NULL, &(struct timeval){ .tv_usec = 500000 }) <= 0)
struct pollfd pfd = { .fd = STDIN_FILENO, .events = POLLIN };
if (poll(&pfd, 1, 500) <= 0)
break;
ssize_t n = read(STDIN_FILENO, buf + len, sizeof buf - 1 - len);
if (n <= 0)
Expand Down Expand Up @@ -1907,41 +1937,41 @@ int
main(int argc, char *argv[]) {
unsigned int key_index = 0;
memset(keys, 0, sizeof(keys));
sigset_t emptyset, blockset;

sigpipe_init();
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);
struct pollfd *pfds = NULL;
size_t pfds_cap = 0;

while (running) {
int r, nfds = 0;
fd_set rd;
int r;
size_t nfds = 0;

if (screen.need_resize) {
resize_screen();
screen.need_resize = false;
}

FD_ZERO(&rd);
FD_SET(STDIN_FILENO, &rd);

if (cmdfifo.fd != -1) {
FD_SET(cmdfifo.fd, &rd);
nfds = cmdfifo.fd;
size_t need = 4;
for (Client *c = clients; c; c = c->next)
need++;
if (need > pfds_cap) {
struct pollfd *p = realloc(pfds, need * sizeof *pfds);
if (!p)
eprint("realloc: %s\n", strerror(errno));
pfds = p;
pfds_cap = need;
}

if (bar.fd != -1) {
FD_SET(bar.fd, &rd);
nfds = MAX(nfds, bar.fd);
}
pfds[nfds++] = (struct pollfd){ .fd = STDIN_FILENO, .events = POLLIN };
pfds[nfds++] = (struct pollfd){ .fd = sigpipe[0], .events = POLLIN };
pfds[nfds++] = (struct pollfd){ .fd = cmdfifo.fd, .events = POLLIN };
pfds[nfds++] = (struct pollfd){ .fd = bar.fd, .events = POLLIN };

for (Client *c = clients; c; ) {
if (c->editor && c->editor_died)
Expand All @@ -1953,22 +1983,25 @@ main(int argc, char *argv[]) {
continue;
}
int pty = c->editor ? vt_pty_get(c->editor) : vt_pty_get(c->app);
FD_SET(pty, &rd);
nfds = MAX(nfds, pty);
c->pollidx = nfds;
pfds[nfds++] = (struct pollfd){ .fd = pty, .events = POLLIN };
c = c->next;
}

doupdate();
r = pselect(nfds + 1, &rd, NULL, NULL, NULL, &emptyset);
r = poll(pfds, nfds, -1);

if (r < 0) {
if (errno == EINTR)
continue;
perror("select()");
perror("poll()");
exit(EXIT_FAILURE);
}

if (FD_ISSET(STDIN_FILENO, &rd)) {
if (pfds[1].revents)
sigpipe_drain();

if (pfds[0].revents) {
int code = getch();
if (code >= 0) {
keys[key_index++] = code;
Expand Down Expand Up @@ -1998,14 +2031,14 @@ main(int argc, char *argv[]) {
continue;
}

if (cmdfifo.fd != -1 && FD_ISSET(cmdfifo.fd, &rd))
if (cmdfifo.fd != -1 && pfds[2].revents)
handle_cmdfifo();

if (bar.fd != -1 && FD_ISSET(bar.fd, &rd))
if (bar.fd != -1 && pfds[3].revents)
handle_statusbar();

for (Client *c = clients; c; c = c->next) {
if (FD_ISSET(vt_pty_get(c->term), &rd)) {
if (c->pollidx && pfds[c->pollidx].fd == vt_pty_get(c->term) && pfds[c->pollidx].revents) {
if (vt_process(c->term) < 0 && errno == EIO) {
if (c->editor)
c->editor_died = true;
Expand Down
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