diff options
Diffstat (limited to 'libusb/os/events_posix.c')
| -rw-r--r-- | libusb/os/events_posix.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/libusb/os/events_posix.c b/libusb/os/events_posix.c index 715a2d5..4056dae 100644 --- a/libusb/os/events_posix.c +++ b/libusb/os/events_posix.c @@ -28,6 +28,31 @@ #ifdef HAVE_TIMERFD #include <sys/timerfd.h> #endif + +#ifdef __EMSCRIPTEN__ +/* On Emscripten `pipe` does not conform to the spec and does not block + * until events are available, which makes it unusable for event system + * and often results in deadlocks when `pipe` is in a loop like it is + * in libusb. + * + * Therefore use a custom event system based on browser event emitters. */ +#include <emscripten.h> +#include <emscripten/atomic.h> +#include <emscripten/threading.h> + +EM_ASYNC_JS(void, em_libusb_wait_async, (const _Atomic int* ptr, int expected_value, int timeout), { + await Atomics.waitAsync(HEAP32, ptr >> 2, expected_value, timeout).value; +}); + +static void em_libusb_wait(const _Atomic int *ptr, int expected_value, int timeout) +{ + if (emscripten_is_main_runtime_thread()) { + em_libusb_wait_async(ptr, expected_value, timeout); + } else { + emscripten_atomic_wait_u32((int*)ptr, expected_value, 1000000LL * timeout); + } +} +#endif #include <unistd.h> #ifdef HAVE_EVENTFD @@ -131,6 +156,10 @@ void usbi_signal_event(usbi_event_t *event) r = write(EVENT_WRITE_FD(event), &dummy, sizeof(dummy)); if (r != sizeof(dummy)) usbi_warn(NULL, "event write failed"); +#ifdef __EMSCRIPTEN__ + event->has_event = 1; + emscripten_atomic_notify(&event->has_event, EMSCRIPTEN_NOTIFY_ALL_WAITERS); +#endif } void usbi_clear_event(usbi_event_t *event) @@ -141,6 +170,9 @@ void usbi_clear_event(usbi_event_t *event) r = read(EVENT_READ_FD(event), &dummy, sizeof(dummy)); if (r != sizeof(dummy)) usbi_warn(NULL, "event read failed"); +#ifdef __EMSCRIPTEN__ + event->has_event = 0; +#endif } #ifdef HAVE_TIMERFD @@ -223,6 +255,14 @@ int usbi_wait_for_events(struct libusb_context *ctx, int internal_fds, num_ready; usbi_dbg(ctx, "poll() %u fds with timeout in %dms", (unsigned int)nfds, timeout_ms); +#ifdef __EMSCRIPTEN__ + // Emscripten's poll doesn't actually block, so we need to use an out-of-band + // waiting signal. + em_libusb_wait(&ctx->event.has_event, 0, timeout_ms); + // Emscripten ignores timeout_ms, but set it to 0 for future-proofing in case + // they ever implement real poll. + timeout_ms = 0; +#endif num_ready = poll(fds, nfds, timeout_ms); usbi_dbg(ctx, "poll() returned %d", num_ready); if (num_ready == 0) { |