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authorJeff Dike <jdike@addtoit.com>2007-10-16 01:26:42 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-16 09:43:04 -0700
commitc59dbcadd5d125ba40595612dc91ab18924164d3 (patch)
treea0970a23641babc6d9b54074316a6686322b69d2
parente99525f9706900417f37721e601d2b414d41bfee (diff)
uml: fix console writing bugs
The previous console cleanup patch switched generic_read and generic_write from calling os_{read,write}_file to calling read and write directly. Because the calling convention is different, they now need to get any error from errno rather than the return value. I did this for generic_read, but forgot about generic_write. While chasing some output corruption, I noticed that line_write was unnecessarily calling flush_buffer, and deleted it. I don't understand why, but the corruption disappeared. This is unneeded because there already is a perfectly good mechanism for finding out when the host output device has some room to write data - there is an interrupt that comes in when writes can happen again. line_write calling flush_buffer seemed to just be an attempt to opportunistically get some data out to the host. I also made write_chan short-circuit calling into the host-level code for zero-length writes. Calling libc write with a length of zero conflated write not being able to write anything with asking it not to write anything. Better to just cut it off as soon as possible. Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/um/drivers/chan_kern.c3
-rw-r--r--arch/um/drivers/chan_user.c11
-rw-r--r--arch/um/drivers/line.c9
3 files changed, 16 insertions, 7 deletions
diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index c09dbdfa298a..db3082b4da46 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -291,6 +291,9 @@ int write_chan(struct list_head *chans, const char *buf, int len,
struct chan *chan = NULL;
int n, ret = 0;
+ if (len == 0)
+ return 0;
+
list_for_each(ele, chans) {
chan = list_entry(ele, struct chan, list);
if (!chan->output || (chan->ops->write == NULL))
diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
index 77557e233f58..d29e56d8ced4 100644
--- a/arch/um/drivers/chan_user.c
+++ b/arch/um/drivers/chan_user.c
@@ -38,7 +38,16 @@ int generic_read(int fd, char *c_out, void *unused)
int generic_write(int fd, const char *buf, int n, void *unused)
{
- return write(fd, buf, n);
+ int err;
+
+ err = write(fd, buf, n);
+ if (err > 0)
+ return err;
+ else if (errno == EAGAIN)
+ return 0;
+ else if (err == 0)
+ return -EIO;
+ return -errno;
}
int generic_window_size(int fd, void *unused, unsigned short *rows_out,
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 3e0b68e297f2..b4538dfb4820 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -216,18 +216,15 @@ int line_write(struct tty_struct *tty, const unsigned char *buf, int len)
{
struct line *line = tty->driver_data;
unsigned long flags;
- int n, err, ret = 0;
+ int n, ret = 0;
if(tty->stopped)
return 0;
spin_lock_irqsave(&line->lock, flags);
- if (line->head != line->tail) {
+ if (line->head != line->tail)
ret = buffer_data(line, buf, len);
- err = flush_buffer(line);
- if (err <= 0 && (err != -EAGAIN || !ret))
- ret = err;
- } else {
+ else {
n = write_chan(&line->chan_list, buf, len,
line->driver->write_irq);
if (n < 0) {