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authorNicholas Piggin <npiggin@gmail.com>2018-04-30 17:55:57 +0300
committerMichael Ellerman <mpe@ellerman.id.au>2018-07-23 13:13:20 +0300
commit9f65b81f36e31563c5a5e4df3b3b8bc7550b6030 (patch)
treea4e3e295eba020c1f68072d40733cdb57f543e84 /drivers/tty
parent550ddadcc7580ec2a6c22d4ed04291bc6e2428fb (diff)
downloadlinux-9f65b81f36e31563c5a5e4df3b3b8bc7550b6030.tar.xz
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: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/hvc/hvc_console.c35
-rw-r--r--drivers/tty/hvc/hvc_console.h1
2 files changed, 34 insertions, 2 deletions
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 6131d5084c42..5414c4a87bea 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -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();
+ }
}
/*
diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h
index ea63090e013f..e9319954c832 100644
--- a/drivers/tty/hvc/hvc_console.h
+++ b/drivers/tty/hvc/hvc_console.h
@@ -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);