git: b6321b9b8499 - stable/15 - uart: fix sleeping while holding mutex in uart_tty_detach()

The branch stable/15 has been updated by kevans:

URL: https://cgit.FreeBSD.org/src/commit/?id=b6321b9b8499376d30bd7ca933ff25aae9877596

commit b6321b9b8499376d30bd7ca933ff25aae9877596
Author:     Abdelkader Boudih <freebsd@seuros.com>
AuthorDate: 2026-02-03 03:21:43 +0000
Commit:     Kyle Evans <kevans@FreeBSD.org>
CommitDate: 2026-04-12 03:15:12 +0000

    uart: fix sleeping while holding mutex in uart_tty_detach()
    
    Move swi_remove() call before acquiring the tty lock. swi_remove() calls
    intr_event_remove_handler() which may sleep via msleep(), causing a lock
    order violation when called with the tty mutex held.
    
    The software interrupt handler removal operates on the interrupt event
    structure independently and does not require the tty lock. This matches
    the pattern used in other drivers such as tcp_hpts.c where swi_remove()
    is called without holding other locks.
    
    Reviewed by:    imp, kevans
    
    (cherry picked from commit ed3a2469a71e0ef48cf8e636c35e64a011756da3)
---
 sys/dev/uart/uart_tty.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sys/dev/uart/uart_tty.c b/sys/dev/uart/uart_tty.c
index d15d1d0c6ac2..7f0f730b3b6e 100644
--- a/sys/dev/uart/uart_tty.c
+++ b/sys/dev/uart/uart_tty.c
@@ -447,8 +447,9 @@ uart_tty_detach(struct uart_softc *sc)
 
 	tp = sc->sc_u.u_tty.tp;
 
-	tty_lock(tp);
 	swi_remove(sc->sc_softih);
+
+	tty_lock(tp);
 	tty_rel_gone(tp);
 
 	return (0);