poller: Raise signals through self-pipe
Signal handling relied on poll(2) being interrupted by signals, followed by a check for signal handlers flagging a signal as received. This only allowed signals that were received during poll(2) to be handled correctly. Implement the usual self-pipe implementation, where signal handlers write an arbitrary byte to a polled file descriptor to ensure proper level-triggered signal handling.
This commit is contained in:
Kenny Levinsen
parent
fb5743971c
commit
6747c5f3f8
3 changed files with 151 additions and 110 deletions
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@ -71,10 +71,11 @@ struct poller {
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struct linked_list signals;
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struct linked_list fds;
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int signal_fds[2];
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struct pollfd *pollfds;
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size_t pollfds_len;
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size_t fd_event_sources;
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bool pollfds_dirty;
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bool dirty;
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};
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/**
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@ -96,7 +97,7 @@ struct poll_impl {
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* Initializes the poller. The poller must be torn down with poller_finish when
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* it is no longer needed.
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*/
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void poller_init(struct poller *poller);
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int poller_init(struct poller *poller);
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/**
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* De-initializes the poller. This destroys all remaining event sources and
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251
seatd/poller.c
251
seatd/poller.c
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@ -1,5 +1,6 @@
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <poll.h>
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#include <signal.h>
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#include <stddef.h>
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@ -41,15 +42,54 @@ struct event_source_signal {
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/* Used for signal handling */
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struct poller *global_poller = NULL;
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void poller_init(struct poller *poller) {
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static void signal_handler(int sig) {
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if (global_poller == NULL) {
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return;
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}
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for (struct linked_list *elem = global_poller->signals.next;
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elem != &global_poller->signals; elem = elem->next) {
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struct event_source_signal *bps = (struct event_source_signal *)elem;
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if (bps->signal == sig) {
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bps->raised = true;
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}
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}
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int saved_errno = errno;
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if (write(global_poller->signal_fds[1], "\0", 1) == -1 && errno != EAGAIN) {
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// This is unfortunate.
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}
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errno = saved_errno;
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}
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static int set_nonblock(int fd) {
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int flags;
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if ((flags = fcntl(fd, F_GETFL)) == -1 || fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
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return -1;
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}
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return 0;
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}
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int poller_init(struct poller *poller) {
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assert(global_poller == NULL);
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if (pipe(poller->signal_fds) == -1) {
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return -1;
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}
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if (set_nonblock(poller->signal_fds[0]) == -1) {
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return -1;
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}
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if (set_nonblock(poller->signal_fds[1]) == -1) {
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return -1;
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}
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linked_list_init(&poller->fds);
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linked_list_init(&poller->signals);
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poller->pollfds = NULL;
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poller->pollfds_len = 0;
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poller->fd_event_sources = 0;
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poller->dirty = true;
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poller->fd_event_sources = 1;
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global_poller = poller;
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return 0;
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}
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int poller_finish(struct poller *poller) {
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@ -74,63 +114,6 @@ int poller_finish(struct poller *poller) {
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return 0;
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}
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static int event_mask_to_poll_mask(uint32_t event_mask) {
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int poll_mask = 0;
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if (event_mask & EVENT_READABLE) {
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poll_mask |= POLLIN;
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}
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if (event_mask & EVENT_WRITABLE) {
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poll_mask |= POLLOUT;
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}
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return poll_mask;
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}
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static uint32_t poll_mask_to_event_mask(int poll_mask) {
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uint32_t event_mask = 0;
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if (poll_mask & POLLIN) {
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event_mask |= EVENT_READABLE;
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}
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if (poll_mask & POLLOUT) {
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event_mask |= EVENT_WRITABLE;
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}
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if (poll_mask & POLLERR) {
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event_mask |= EVENT_ERROR;
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}
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if (poll_mask & POLLHUP) {
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event_mask |= EVENT_HANGUP;
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}
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return event_mask;
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}
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static int regenerate_pollfds(struct poller *poller) {
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if (!poller->pollfds_dirty) {
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return 0;
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}
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if (poller->fd_event_sources > poller->pollfds_len) {
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struct pollfd *fds = calloc(poller->fd_event_sources, sizeof(struct pollfd));
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if (fds == NULL) {
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return -1;
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}
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free(poller->pollfds);
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poller->pollfds = fds;
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poller->pollfds_len = poller->fd_event_sources;
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}
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ssize_t idx = 0;
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for (struct linked_list *elem = poller->fds.next; elem != &poller->fds; elem = elem->next) {
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struct event_source_fd *bpfd = (struct event_source_fd *)elem;
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bpfd->pollfd_idx = idx++;
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poller->pollfds[bpfd->pollfd_idx] = (struct pollfd){
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.fd = bpfd->fd,
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.events = event_mask_to_poll_mask(bpfd->mask),
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};
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}
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poller->pollfds_dirty = false;
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return 0;
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}
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struct event_source_fd *poller_add_fd(struct poller *poller, int fd, uint32_t mask,
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event_source_fd_func_t func, void *data) {
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struct event_source_fd *bpfd = calloc(1, sizeof(struct event_source_fd));
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@ -144,7 +127,7 @@ struct event_source_fd *poller_add_fd(struct poller *poller, int fd, uint32_t ma
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bpfd->poller = poller;
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bpfd->pollfd_idx = -1;
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poller->fd_event_sources += 1;
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poller->pollfds_dirty = true;
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poller->dirty = true;
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linked_list_insert(&poller->fds, &bpfd->link);
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return (struct event_source_fd *)bpfd;
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}
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@ -153,7 +136,7 @@ int event_source_fd_destroy(struct event_source_fd *event_source) {
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struct event_source_fd *bpfd = (struct event_source_fd *)event_source;
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struct poller *poller = bpfd->poller;
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poller->fd_event_sources -= 1;
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poller->pollfds_dirty = true;
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poller->dirty = true;
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bpfd->killed = true;
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return 0;
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}
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@ -162,23 +145,10 @@ int event_source_fd_update(struct event_source_fd *event_source, uint32_t mask)
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struct event_source_fd *bpfd = (struct event_source_fd *)event_source;
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struct poller *poller = bpfd->poller;
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event_source->mask = mask;
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poller->pollfds_dirty = true;
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poller->dirty = true;
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return 0;
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}
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static void signal_handler(int sig) {
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if (global_poller == NULL) {
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return;
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}
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for (struct linked_list *elem = global_poller->signals.next;
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elem != &global_poller->signals; elem = elem->next) {
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struct event_source_signal *bps = (struct event_source_signal *)elem;
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if (bps->signal == sig) {
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bps->raised = true;
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}
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}
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}
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struct event_source_signal *poller_add_signal(struct poller *poller, int signal,
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event_source_signal_func_t func, void *data) {
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@ -224,17 +194,101 @@ int event_source_signal_destroy(struct event_source_signal *event_source) {
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sigaction(bps->signal, &sa, NULL);
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}
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poller->dirty = true;
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bps->killed = true;
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return 0;
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}
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int poller_poll(struct poller *poller) {
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if (regenerate_pollfds(poller) == -1) {
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return -1;
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static int event_mask_to_poll_mask(uint32_t event_mask) {
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int poll_mask = 0;
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if (event_mask & EVENT_READABLE) {
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poll_mask |= POLLIN;
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}
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if (event_mask & EVENT_WRITABLE) {
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poll_mask |= POLLOUT;
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}
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return poll_mask;
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}
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static uint32_t poll_mask_to_event_mask(int poll_mask) {
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uint32_t event_mask = 0;
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if (poll_mask & POLLIN) {
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event_mask |= EVENT_READABLE;
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}
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if (poll_mask & POLLOUT) {
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event_mask |= EVENT_WRITABLE;
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}
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if (poll_mask & POLLERR) {
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event_mask |= EVENT_ERROR;
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}
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if (poll_mask & POLLHUP) {
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event_mask |= EVENT_HANGUP;
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}
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return event_mask;
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}
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static int regenerate(struct poller *poller) {
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if (poller->fd_event_sources > poller->pollfds_len) {
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struct pollfd *fds =
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realloc(poller->pollfds, poller->fd_event_sources * sizeof(struct pollfd));
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if (fds == NULL) {
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return -1;
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}
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poller->pollfds = fds;
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poller->pollfds_len = poller->fd_event_sources;
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}
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if (poll(poller->pollfds, poller->fd_event_sources, -1) == -1 && errno != EINTR) {
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return -1;
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size_t idx = 0;
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poller->pollfds[idx++] = (struct pollfd){
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.fd = poller->signal_fds[0],
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.events = POLLIN,
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};
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for (struct linked_list *elem = poller->fds.next; elem != &poller->fds; elem = elem->next) {
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struct event_source_fd *bpfd = (struct event_source_fd *)elem;
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if (bpfd->killed) {
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elem = elem->prev;
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linked_list_remove(&bpfd->link);
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free(bpfd);
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} else {
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bpfd->pollfd_idx = idx++;
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assert(bpfd->pollfd_idx < (ssize_t)poller->pollfds_len);
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poller->pollfds[bpfd->pollfd_idx] = (struct pollfd){
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.fd = bpfd->fd,
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.events = event_mask_to_poll_mask(bpfd->mask),
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};
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}
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}
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assert(idx == poller->fd_event_sources);
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for (struct linked_list *elem = poller->signals.next; elem != &poller->signals;
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elem = elem->next) {
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struct event_source_signal *bps = (struct event_source_signal *)elem;
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if (bps->killed) {
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elem = elem->prev;
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linked_list_remove(&bps->link);
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free(bps);
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}
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}
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return 0;
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}
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static void dispatch(struct poller *poller) {
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if ((poller->pollfds[0].revents & POLLIN) != 0) {
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char garbage[8];
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while (read(poller->signal_fds[0], &garbage, sizeof garbage) != -1) {
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}
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for (struct linked_list *elem = poller->signals.next; elem != &poller->signals;
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elem = elem->next) {
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struct event_source_signal *bps = (struct event_source_signal *)elem;
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if (!bps->raised || bps->killed) {
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continue;
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}
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bps->func(bps->signal, bps->data);
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bps->raised = false;
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}
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}
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for (struct linked_list *elem = poller->fds.next; elem != &poller->fds; elem = elem->next) {
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@ -242,6 +296,7 @@ int poller_poll(struct poller *poller) {
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if (bpfd->pollfd_idx == -1 || bpfd->killed) {
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continue;
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}
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assert(bpfd->pollfd_idx < (ssize_t)poller->pollfds_len);
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short revents = poller->pollfds[bpfd->pollfd_idx].revents;
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if (revents == 0) {
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continue;
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@ -249,39 +304,21 @@ int poller_poll(struct poller *poller) {
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bpfd->func(poller->pollfds[bpfd->pollfd_idx].fd, poll_mask_to_event_mask(revents),
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bpfd->data);
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}
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}
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for (struct linked_list *elem = poller->signals.next; elem != &poller->signals;
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elem = elem->next) {
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struct event_source_signal *bps = (struct event_source_signal *)elem;
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if (!bps->raised || bps->killed) {
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continue;
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int poller_poll(struct poller *poller) {
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if (poller->dirty) {
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if (regenerate(poller) == -1) {
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return -1;
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}
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bps->func(bps->signal, bps->data);
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bps->raised = false;
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poller->dirty = false;
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}
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for (struct linked_list *elem = poller->fds.next; elem != &poller->fds; elem = elem->next) {
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struct event_source_fd *bpfd = (struct event_source_fd *)elem;
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if (!bpfd->killed) {
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continue;
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}
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elem = elem->prev;
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linked_list_remove(&bpfd->link);
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free(bpfd);
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if (poll(poller->pollfds, poller->fd_event_sources, -1) == -1 && errno != EINTR) {
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return -1;
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}
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for (struct linked_list *elem = poller->signals.next; elem != &poller->signals;
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elem = elem->next) {
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struct event_source_signal *bps = (struct event_source_signal *)elem;
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if (!bps->killed) {
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continue;
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}
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elem = elem->prev;
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linked_list_remove(&bps->link);
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free(bps);
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}
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dispatch(poller);
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return 0;
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}
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@ -23,7 +23,10 @@ static int server_handle_vt_rel(int signal, void *data);
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static int server_handle_kill(int signal, void *data);
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int server_init(struct server *server) {
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poller_init(&server->poller);
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if (poller_init(&server->poller) == -1) {
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log_errorf("could not initialize poller: %s", strerror(errno));
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return -1;
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}
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linked_list_init(&server->seats);
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linked_list_init(&server->idle_clients);
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