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Fix tty_drain() and, thus, TIOCDRAIN of the current tty(4) incarnation

Browse source 
to actually wait until the TX FIFOs of UARTs have be drained before
returning. This is done by bringing the equivalent of the TS_BUSY flag
found in the previous implementation back in an ABI-preserving way.
Reported and tested by: Patrick Powell

Most likely, drivers for USB-serial-adapters likewise incorporating
TX FIFOs as well as other terminal devices that buffer output in some
form should also provide implementations of tsw_busy.

MFC after:	3 days
This commit is contained in:
Marius Strobl 2016-01-19 23:34:27 +00:00
parent eb2ad8724b
commit 9750d9e5b6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=294362
3 changed files with 36 additions and 3 deletions
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13
sys/dev/uart/uart_tty.c
View file

@ -355,6 +355,18 @@ uart_tty_free(void *arg)
*/
}
static bool
uart_tty_busy(struct tty *tp)
{
struct uart_softc *sc;
sc = tty_softc(tp);
if (sc == NULL || sc->sc_leaving)
return (FALSE);
return (sc->sc_txbusy);
}
static struct ttydevsw uart_tty_class = {
.tsw_flags = TF_INITLOCK|TF_CALLOUT,
.tsw_open = uart_tty_open,
@ -365,6 +377,7 @@ static struct ttydevsw uart_tty_class = {
.tsw_param = uart_tty_param,
.tsw_modem = uart_tty_modem,
.tsw_free = uart_tty_free,
.tsw_busy = uart_tty_busy,
};
int

12
sys/kern/tty.c
View file

@ -132,11 +132,11 @@ tty_drain(struct tty *tp, int leaving)
/* buffer is inaccessible */
return (0);
while (ttyoutq_bytesused(&tp->t_outq) > 0) {
while (ttyoutq_bytesused(&tp->t_outq) > 0 || ttydevsw_busy(tp)) {
ttydevsw_outwakeup(tp);
/* Could be handled synchronously. */
bytesused = ttyoutq_bytesused(&tp->t_outq);
if (bytesused == 0)
if (bytesused == 0 && !ttydevsw_busy(tp))
return (0);
/* Wait for data to be drained. */
@ -955,6 +955,13 @@ ttydevsw_deffree(void *softc)
panic("Terminal device freed without a free-handler");
}
static bool
ttydevsw_defbusy(struct tty *tp __unused)
{
return (FALSE);
}
/*
* TTY allocation and deallocation. TTY devices can be deallocated when
* the driver doesn't use it anymore, when the TTY isn't a session's
@ -989,6 +996,7 @@ tty_alloc_mutex(struct ttydevsw *tsw, void *sc, struct mtx *mutex)
PATCH_FUNC(mmap);
PATCH_FUNC(pktnotify);
PATCH_FUNC(free);
PATCH_FUNC(busy);
#undef PATCH_FUNC
tp = malloc(sizeof(struct tty), M_TTY, M_WAITOK|M_ZERO);

14
sys/sys/ttydevsw.h
View file

@ -54,6 +54,7 @@ typedef int tsw_mmap_t(struct tty *tp, vm_ooffset_t offset,
vm_paddr_t * paddr, int nprot, vm_memattr_t *memattr);
typedef void tsw_pktnotify_t(struct tty *tp, char event);
typedef void tsw_free_t(void *softc);
typedef bool tsw_busy_t(struct tty *tp);
struct ttydevsw {
unsigned int tsw_flags; /* Default TTY flags. */
@ -74,7 +75,9 @@ struct ttydevsw {
tsw_free_t *tsw_free; /* Destructor. */
void *tsw_spare[4]; /* For future use. */
tsw_busy_t *tsw_busy; /* Draining output. */
void *tsw_spare[3]; /* For future use. */
};
static __inline int
@ -181,4 +184,13 @@ ttydevsw_free(struct tty *tp)
tp->t_devsw->tsw_free(tty_softc(tp));
}
static __inline bool
ttydevsw_busy(struct tty *tp)
{
MPASS(tty_gone(tp));
return (tp->t_devsw->tsw_busy(tp));
}
#endif /* !_SYS_TTYDEVSW_H_ */