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

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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: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2018-05-01 00:55:57 +10:00 committed by Michael Ellerman
parent 550ddadcc7
commit 9f65b81f36
2 changed files with 34 additions and 2 deletions
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35
drivers/tty/hvc/hvc_console.c
View File

@ -110,6 +110,29 @@ static struct hvc_struct *hvc_get_by_index(int index)
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
* 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) {
/* throw away characters on error
* but spin in case of -EAGAIN */
if (r != -EAGAIN)
if (r != -EAGAIN) {
i = 0;
} else {
hvc_console_flush(cons_ops[index],
vtermnos[index]);
}
} else if (r > 0) {
i -= r;
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)
@ -513,8 +541,11 @@ static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count
spin_unlock_irqrestore(&hp->lock, flags);
if (count)
if (count) {
if (hp->n_outbuf > 0)
hvc_flush(hp);
cond_resched();
}
}
/*

1
drivers/tty/hvc/hvc_console.h
View File

@ -54,6 +54,7 @@ struct hvc_struct {
struct hv_ops {
int (*get_chars)(uint32_t vtermno, 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 */
int (*notifier_add)(struct hvc_struct *hp, int irq);