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Commit 9f65b81f authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

tty: hvc: introduce the hv_ops.flush operation for hvc drivers 



Use .flush to wait for drivers to flush their console outside of
the spinlock, to reduce lock/irq latencies.

Flush the hvc console driver after each write, which can help
messages make it out to the console after a crash.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 550ddadc

drivers/tty/hvc/hvc_console.c

+33 −2
Original line number Original line Diff line number Diff line
@@ -110,6 +110,29 @@ static struct hvc_struct *hvc_get_by_index(int index) 
	return hp;

	return hp;

}

}





static int __hvc_flush(const struct hv_ops *ops, uint32_t vtermno, bool wait)

{

	if (wait)

		might_sleep();



	if (ops->flush)

		return ops->flush(vtermno, wait);

	return 0;

}



static int hvc_console_flush(const struct hv_ops *ops, uint32_t vtermno)

{

	return __hvc_flush(ops, vtermno, false);

}



/*

 * Wait for the console to flush before writing more to it. This sleeps.

 */

static int hvc_flush(struct hvc_struct *hp)

{

	return __hvc_flush(hp->ops, hp->vtermno, true);

}



/*

/*

 * Initial console vtermnos for console API usage prior to full console

 * Initial console vtermnos for console API usage prior to full console

 * initialization.  Any vty adapter outside this range will not have usable

 * initialization.  Any vty adapter outside this range will not have usable
@@ -155,8 +178,12 @@ static void hvc_console_print(struct console *co, const char *b, 
			if (r <= 0) {

			if (r <= 0) {

				/* throw away characters on error

				/* throw away characters on error

				 * but spin in case of -EAGAIN */

				 * but spin in case of -EAGAIN */

				if (r != -EAGAIN)

				if (r != -EAGAIN) {

					i = 0;

					i = 0;

				} else {

					hvc_console_flush(cons_ops[index],

						      vtermnos[index]);

				}

			} else if (r > 0) {

			} else if (r > 0) {

				i -= r;

				i -= r;

				if (i > 0)

				if (i > 0)
@@ -164,6 +191,7 @@ static void hvc_console_print(struct console *co, const char *b, 
			}

			}

		}

		}

	}

	}

	hvc_console_flush(cons_ops[index], vtermnos[index]);

}

}





static struct tty_driver *hvc_console_device(struct console *c, int *index)

static struct tty_driver *hvc_console_device(struct console *c, int *index)
@@ -513,9 +541,12 @@ static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count 




		spin_unlock_irqrestore(&hp->lock, flags);

		spin_unlock_irqrestore(&hp->lock, flags);





		if (count)

		if (count) {

			if (hp->n_outbuf > 0)

				hvc_flush(hp);

			cond_resched();

			cond_resched();

		}

		}

	}





	/*

	/*

	 * Racy, but harmless, kick thread if there is still pending data.

	 * Racy, but harmless, kick thread if there is still pending data.

drivers/tty/hvc/hvc_console.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -54,6 +54,7 @@ struct hvc_struct { 
struct hv_ops {

struct hv_ops {

	int (*get_chars)(uint32_t vtermno, char *buf, int count);

	int (*get_chars)(uint32_t vtermno, char *buf, int count);

	int (*put_chars)(uint32_t vtermno, const char *buf, int count);

	int (*put_chars)(uint32_t vtermno, const char *buf, int count);

	int (*flush)(uint32_t vtermno, bool wait);





	/* Callbacks for notification. Called in open, close and hangup */

	/* Callbacks for notification. Called in open, close and hangup */

	int (*notifier_add)(struct hvc_struct *hp, int irq);

	int (*notifier_add)(struct hvc_struct *hp, int irq);