git: 28d6ffe37cf9 - main - eventfd: Add eventfd_signal()

The branch main has been updated by dumbbell:

URL: https://cgit.FreeBSD.org/src/commit/?id=28d6ffe37cf928c5b13e0aa34c39c4414a0f09e4

commit 28d6ffe37cf928c5b13e0aa34c39c4414a0f09e4
Author:     Jean-Sébastien Pédron <dumbbell@FreeBSD.org>
AuthorDate: 2025-05-26 17:36:49 +0000
Commit:     Jean-Sébastien Pédron <dumbbell@FreeBSD.org>
CommitDate: 2026-01-25 16:04:44 +0000

    eventfd: Add eventfd_signal()
    
    The `eventfd_signal()` function is the equivalent to a write to an
    eventfd file descriptor: it bumps the internal counter and wakes up
    processes waiting for it.
    
    `eventfd_signal()` is meant to be used by kernel drivers. DRM drivers
    will call it through linuxkpi.
    
    Reviewed by:    markj
    Sponsored by:   The FreeBSD Foundation
    Differential Revision: https://reviews.freebsd.org/D50850
---
 sys/kern/sys_eventfd.c | 25 ++++++++++++++++++++++---
 sys/sys/eventfd.h      |  1 +
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/sys/kern/sys_eventfd.c b/sys/kern/sys_eventfd.c
index 433bcb57b2b3..47f1fcc316ec 100644
--- a/sys/kern/sys_eventfd.c
+++ b/sys/kern/sys_eventfd.c
@@ -157,6 +157,27 @@ eventfd_put(struct eventfd *efd)
 	free(efd, M_EVENTFD);
 }
 
+static void
+eventfd_wakeup(struct eventfd *efd)
+{
+	KNOTE_LOCKED(&efd->efd_sel.si_note, 0);
+	selwakeup(&efd->efd_sel);
+	wakeup(&efd->efd_count);
+}
+
+void
+eventfd_signal(struct eventfd *efd)
+{
+	mtx_lock(&efd->efd_lock);
+
+	if (efd->efd_count < UINT64_MAX)
+		efd->efd_count++;
+
+	eventfd_wakeup(efd);
+
+	mtx_unlock(&efd->efd_lock);
+}
+
 static int
 eventfd_close(struct file *fp, struct thread *td)
 {
@@ -244,9 +265,7 @@ retry:
 	if (error == 0) {
 		MPASS(UINT64_MAX - efd->efd_count > count);
 		efd->efd_count += count;
-		KNOTE_LOCKED(&efd->efd_sel.si_note, 0);
-		selwakeup(&efd->efd_sel);
-		wakeup(&efd->efd_count);
+		eventfd_wakeup(efd);
 	}
 	mtx_unlock(&efd->efd_lock);
 
diff --git a/sys/sys/eventfd.h b/sys/sys/eventfd.h
index 1f36dbecb92d..1b390feed48e 100644
--- a/sys/sys/eventfd.h
+++ b/sys/sys/eventfd.h
@@ -44,6 +44,7 @@ int eventfd_create_file(struct thread *td, struct file *fp, uint32_t initval,
     int flags);
 struct eventfd *eventfd_get(struct file *fp);
 void eventfd_put(struct eventfd *efd);
+void eventfd_signal(struct eventfd *efd);
 
 #else