git: 884ca28b97e7 - stable/14 - libusb: use eventfd

The branch stable/14 has been updated by bapt:

URL: https://cgit.FreeBSD.org/src/commit/?id=884ca28b97e73f297b512aaf04deb6f951854c02

commit 884ca28b97e73f297b512aaf04deb6f951854c02
Author:     Baptiste Daroussin <bapt@FreeBSD.org>
AuthorDate: 2025-05-15 13:21:50 +0000
Commit:     Baptiste Daroussin <bapt@FreeBSD.org>
CommitDate: 2025-06-23 07:40:33 +0000

    libusb: use eventfd
    
    Simplify libusb code by replacing pipe(2) inter thread event mecanism
    with eventfd(2).
    
    MFC After:      3 weeks
    Reviewed by:    kevans
    Differential Revision:  https://reviews.freebsd.org/D50360
    
    (cherry picked from commit ae28929b7c78267815e994e0ad12e3cc7db361bc)
---
 lib/libusb/libusb10.c    | 20 +++++++-------------
 lib/libusb/libusb10.h    |  2 +-
 lib/libusb/libusb10_io.c |  5 ++---
 3 files changed, 10 insertions(+), 17 deletions(-)

diff --git a/lib/libusb/libusb10.c b/lib/libusb/libusb10.c
index 6d9c11910ea0..5564bfd8b499 100644
--- a/lib/libusb/libusb10.c
+++ b/lib/libusb/libusb10.c
@@ -39,6 +39,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <time.h>
+#include <sys/eventfd.h>
 #include <sys/fcntl.h>
 #include <sys/ioctl.h>
 #include <sys/queue.h>
@@ -118,15 +119,13 @@ libusb_set_nonblocking(int f)
 void
 libusb_interrupt_event_handler(libusb_context *ctx)
 {
-	uint8_t dummy;
 	int err;
 
 	if (ctx == NULL)
 		return;
 
-	dummy = 0;
-	err = write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
-	if (err < (int)sizeof(dummy)) {
+	err = eventfd_write(ctx->event, 1);
+	if (err < 0) {
 		/* ignore error, if any */
 		DPRINTF(ctx, LIBUSB_DEBUG_FUNCTION, "Waking up event loop failed!");
 	}
@@ -145,7 +144,6 @@ libusb_init_context(libusb_context **context,
 	struct libusb_context *ctx;
 	pthread_condattr_t attr;
 	char *debug, *ep;
-	int ret;
 
 	if (num_options < 0)
 		return (LIBUSB_ERROR_INVALID_PARAM);
@@ -233,19 +231,16 @@ libusb_init_context(libusb_context **context,
 	ctx->ctx_handler = NO_THREAD;
 	ctx->hotplug_handler = NO_THREAD;
 
-	ret = pipe(ctx->ctrl_pipe);
-	if (ret < 0) {
+	ctx->event = eventfd(0, EFD_NONBLOCK);
+	if (ctx->event < 0) {
 		pthread_mutex_destroy(&ctx->ctx_lock);
 		pthread_mutex_destroy(&ctx->hotplug_lock);
 		pthread_cond_destroy(&ctx->ctx_cond);
 		free(ctx);
 		return (LIBUSB_ERROR_OTHER);
 	}
-	/* set non-blocking mode on the control pipe to avoid deadlock */
-	libusb_set_nonblocking(ctx->ctrl_pipe[0]);
-	libusb_set_nonblocking(ctx->ctrl_pipe[1]);
 
-	libusb10_add_pollfd(ctx, &ctx->ctx_poll, NULL, ctx->ctrl_pipe[0], POLLIN);
+	libusb10_add_pollfd(ctx, &ctx->ctx_poll, NULL, ctx->event, POLLIN);
 
 	pthread_mutex_lock(&default_context_lock);
 	if (usbi_default_context == NULL) {
@@ -288,8 +283,7 @@ libusb_exit(libusb_context *ctx)
 	/* XXX cleanup devices */
 
 	libusb10_remove_pollfd(ctx, &ctx->ctx_poll);
-	close(ctx->ctrl_pipe[0]);
-	close(ctx->ctrl_pipe[1]);
+	close(ctx->event);
 	pthread_mutex_destroy(&ctx->ctx_lock);
 	pthread_mutex_destroy(&ctx->hotplug_lock);
 	pthread_cond_destroy(&ctx->ctx_cond);
diff --git a/lib/libusb/libusb10.h b/lib/libusb/libusb10.h
index 544364386061..47d918959f63 100644
--- a/lib/libusb/libusb10.h
+++ b/lib/libusb/libusb10.h
@@ -93,7 +93,7 @@ TAILQ_HEAD(libusb_device_head, libusb_device);
 struct libusb_context {
 	int	debug;
 	int	debug_fixed;
-	int	ctrl_pipe[2];
+	int	event;
 	int	tr_done_ref;
 	int	tr_done_gen;
 
diff --git a/lib/libusb/libusb10_io.c b/lib/libusb/libusb10_io.c
index 2790142486ba..f1e31c2a7416 100644
--- a/lib/libusb/libusb10_io.c
+++ b/lib/libusb/libusb10_io.c
@@ -36,6 +36,7 @@
 #include <string.h>
 #include <time.h>
 #include <unistd.h>
+#include <sys/eventfd.h>
 #include <sys/queue.h>
 #include <sys/endian.h>
 #endif
@@ -187,10 +188,8 @@ libusb10_handle_events_sub(struct libusb_context *ctx, struct timeval *tv)
 			CTX_LOCK(ctx);
 
 		} else {
-			uint8_t dummy;
+			eventfd_read(fds[i].fd, &(eventfd_t){0});
 
-			while (read(fds[i].fd, &dummy, 1) == 1)
-				;
 		}
 	}