bhyve: Move lock of uart frontend to uart backend

Currently, lock of uart in bhyve is placed in frontend. There are some
problems about it:

1. If every frontend should has a lock, why not move it inside backend
   as they all have same uart_softc.
2. If backend needs to modify the information of uart after initialize,
   it will be impossible as backend cannot use lock. For example, if we
   want implement a telnet support for uart in backend, It should wait
   for connection when initialize. After some remote process connect it,
   it needs to modify rfd and wfd in backend.

So I decide to move it to backend.

Reviewed by:	corvink, jhb, markj
Differential Revision:	https://reviews.freebsd.org/D44947

usr.sbin/bhyve/uart_backend.c

@@ -35,6 +35,7 @@
 #include <assert.h>
 #include <capsicum_helpers.h>
 #include <err.h>
+#include <pthread.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
@@ -66,6 +67,7 @@ struct uart_softc {
 	struct ttyfd	tty;
 	struct fifo	rxfifo;
 	struct mevent	*mev;
+	pthread_mutex_t mtx;
 };
 
 static bool uart_stdio;		/* stdio in use for i/o */
@@ -325,7 +327,13 @@ uart_tty_backend(struct uart_softc *sc, const char *path)
 struct uart_softc *
 uart_init(void)
 {
-	return (calloc(1, sizeof(struct uart_softc)));
+	struct uart_softc *sc = calloc(1, sizeof(struct uart_softc));
+	if (sc == NULL)
+		return (NULL);
+
+	pthread_mutex_init(&sc->mtx, NULL);
+
+	return (sc);
 }
 
 int
@@ -346,3 +354,15 @@ uart_tty_open(struct uart_softc *sc, const char *path,
 
 	return (retval);
 }
+
+void
+uart_softc_lock(struct uart_softc *sc)
+{
+	pthread_mutex_lock(&sc->mtx);
+}
+
+void
+uart_softc_unlock(struct uart_softc *sc)
+{
+	pthread_mutex_unlock(&sc->mtx);
+}

usr.sbin/bhyve/uart_backend.h

@@ -51,5 +51,6 @@ int	uart_rxfifo_snapshot(struct uart_softc *sc,
 struct uart_softc *uart_init(void);
 int	uart_tty_open(struct uart_softc *sc, const char *path,
 	    void (*drain)(int, enum ev_type, void *), void *arg);
-
+void	uart_softc_lock(struct uart_softc *sc);
+void	uart_softc_unlock(struct uart_softc *sc);
 #endif /* _UART_BACKEND_H_ */

usr.sbin/bhyve/uart_emul.c

@@ -83,7 +83,6 @@ static struct {
 struct uart_ns16550_softc {
 	struct uart_softc *backend;
 
-	pthread_mutex_t mtx;	/* protects all softc elements */
 	uint8_t	data;		/* Data register (R/W) */
 	uint8_t ier;		/* Interrupt enable register (R/W) */
 	uint8_t lcr;		/* Line control register (R/W) */
@@ -204,14 +203,14 @@ uart_drain(int fd __unused, enum ev_type ev, void *arg)
 	 * to take out the softc lock to protect against concurrent
 	 * access from a vCPU i/o exit
 	 */
-	pthread_mutex_lock(&sc->mtx);
+	uart_softc_lock(sc->backend);
 
 	loopback = (sc->mcr & MCR_LOOPBACK) != 0;
 	uart_rxfifo_drain(sc->backend, loopback);
 	if (!loopback)
 		uart_toggle_intr(sc);
 
-	pthread_mutex_unlock(&sc->mtx);
+	uart_softc_unlock(sc->backend);
 }
 
 void
@@ -220,7 +219,7 @@ uart_ns16550_write(struct uart_ns16550_softc *sc, int offset, uint8_t value)
 	int fifosz;
 	uint8_t msr;
 
-	pthread_mutex_lock(&sc->mtx);
+	uart_softc_lock(sc->backend);
 
 	/*
 	 * Take care of the special case DLAB accesses first
@@ -329,7 +328,7 @@ uart_ns16550_write(struct uart_ns16550_softc *sc, int offset, uint8_t value)
 
 done:
 	uart_toggle_intr(sc);
-	pthread_mutex_unlock(&sc->mtx);
+	uart_softc_unlock(sc->backend);
 }
 
 uint8_t
@@ -337,7 +336,7 @@ uart_ns16550_read(struct uart_ns16550_softc *sc, int offset)
 {
 	uint8_t iir, intr_reason, reg;
 
-	pthread_mutex_lock(&sc->mtx);
+	uart_softc_lock(sc->backend);
 
 	/*
 	 * Take care of the special case DLAB accesses first
@@ -414,7 +413,7 @@ uart_ns16550_read(struct uart_ns16550_softc *sc, int offset)
 
 done:
 	uart_toggle_intr(sc);
-	pthread_mutex_unlock(&sc->mtx);
+	uart_softc_unlock(sc->backend);
 
 	return (reg);
 }
@@ -446,8 +445,6 @@ uart_ns16550_init(uart_intr_func_t intr_assert, uart_intr_func_t intr_deassert,
 	sc->intr_deassert = intr_deassert;
 	sc->backend = uart_init();
 
-	pthread_mutex_init(&sc->mtx, NULL);
-
 	uart_reset(sc);
 
 	return (sc);

usr.sbin/bhyve/uart_pl011.c

@@ -31,7 +31,6 @@
 #include <sys/param.h>
 
 #include <assert.h>
-#include <pthread.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -106,7 +105,6 @@
 
 struct uart_pl011_softc {
 	struct uart_softc *backend;
-	pthread_mutex_t mtx;	/* protects all softc elements */
 
 	uint16_t	irq_state;
 
@@ -184,7 +182,7 @@ uart_drain(int fd __unused, enum ev_type ev, void *arg)
 	 * to take out the softc lock to protect against concurrent
 	 * access from a vCPU i/o exit
 	 */
-	pthread_mutex_lock(&sc->mtx);
+	uart_softc_lock(sc->backend);
 
 	old_size = uart_rxfifo_numchars(sc->backend);
 
@@ -202,7 +200,7 @@ uart_drain(int fd __unused, enum ev_type ev, void *arg)
 	if (!loopback)
 		uart_toggle_intr(sc);
 
-	pthread_mutex_unlock(&sc->mtx);
+	uart_softc_unlock(sc->backend);
 }
 
 void
@@ -210,7 +208,7 @@ uart_pl011_write(struct uart_pl011_softc *sc, int offset, uint32_t value)
 {
 	bool loopback;
 
-	pthread_mutex_lock(&sc->mtx);
+	uart_softc_lock(sc->backend);
 	switch (offset) {
 	case UARTDR:
 		loopback = (sc->cr & UARTCR_LBE) != 0;
@@ -266,7 +264,7 @@ uart_pl011_write(struct uart_pl011_softc *sc, int offset, uint32_t value)
 		break;
 	}
 	uart_toggle_intr(sc);
-	pthread_mutex_unlock(&sc->mtx);
+	uart_softc_unlock(sc->backend);
 }
 
 uint32_t
@@ -276,7 +274,7 @@ uart_pl011_read(struct uart_pl011_softc *sc, int offset)
 	int fifo_sz;
 
 	reg = 0;
-	pthread_mutex_lock(&sc->mtx);
+	uart_softc_lock(sc->backend);
 	switch (offset) {
 	case UARTDR:
 		reg = uart_rxfifo_getchar(sc->backend);
@@ -362,7 +360,7 @@ uart_pl011_read(struct uart_pl011_softc *sc, int offset)
 		break;
 	}
 	uart_toggle_intr(sc);
-	pthread_mutex_unlock(&sc->mtx);
+	uart_softc_unlock(sc->backend);
 
 	return (reg);
 }
@@ -380,8 +378,6 @@ uart_pl011_init(uart_intr_func_t intr_assert, uart_intr_func_t intr_deassert,
 	sc->intr_deassert = intr_deassert;
 	sc->backend = uart_init();
 
-	pthread_mutex_init(&sc->mtx, NULL);
-
 	uart_reset(sc);
 
 	return (sc);