This patch corrects the problem noted but left unfixed by commit
23198fda7182969b619613a555f8645fdc3dc334 "tty: fix chars_in_buffers".
The tty_operation chars_in_buffer() should return zero, not a
negative value, in the error case.
Impact: error handling bugfix
Signed-off-by: Tilman Schmidt <redacted>
---
I only just noticed the "tty: fix chars_in_buffers" patch going in.
Please merge this follow-up fix for 2.6.31, too. Thanks.
drivers/isdn/gigaset/interface.c | 18 +++++++-----------
1 files changed, 7 insertions(+), 11 deletions(-)
diff --git a/drivers/isdn/gigaset/interface.c b/drivers/isdn/gigaset/interface.c
index 8b62df8..dfeec68 100644
--- a/drivers/isdn/gigaset/interface.c
+++ b/drivers/isdn/gigaset/interface.c
@@ -408,33 +408,29 @@ static int if_write_room(struct tty_struct *tty)
return retval;
}
-/* FIXME: This function does not have error returns */
-
static int if_chars_in_buffer(struct tty_struct *tty)
{
struct cardstate *cs;
- int retval = -ENODEV;
+ int retval = 0;
cs = (struct cardstate *) tty->driver_data;
if (!cs) {
pr_err("%s: no cardstate\n", __func__);
- return -ENODEV;
+ return 0;
}
gig_dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __func__);
if (mutex_lock_interruptible(&cs->mutex))
- return -ERESTARTSYS; // FIXME -EINTR?
+ return 0;
- if (!cs->connected) {
+ if (!cs->connected)
gig_dbg(DEBUG_IF, "not connected");
- retval = -ENODEV;
- } else if (!cs->open_count)
+ else if (!cs->open_count)
dev_warn(cs->dev, "%s: device not opened\n", __func__);
- else if (cs->mstate != MS_LOCKED) {
+ else if (cs->mstate != MS_LOCKED)
dev_warn(cs->dev, "can't write to unlocked device\n");
- retval = -EBUSY;
- } else
+ else
retval = cs->ops->chars_in_buffer(cs);
mutex_unlock(&cs->mutex);--
1.6.2.1.214.ge986c
On Sat, 1 Aug 2009 14:18:51 +0200 (CEST)
Tilman Schmidt [off-list ref] wrote:
This patch corrects the problem noted but left unfixed by commit
23198fda7182969b619613a555f8645fdc3dc334 "tty: fix chars_in_buffers".
The tty_operation chars_in_buffer() should return zero, not a
negative value, in the error case.
Is that correct. If you take a signal so the mutex_lock_interruptible
takes the error path we'll exit any waits for characters to be flushed
from buffers and lose the bytes in some cases ? Thats why I didn't
convert it - I didn't understand why it was using _interruptible at all ?
Alan
Hi Alan,
thanks a lot for getting in contact with me, and for your
explanation of the rationale behind your patch.
On Sat, 1 Aug 2009 17:11:41 +0100, Alan Cox wrote:
Is that correct. If you take a signal so the mutex_lock_interruptible
takes the error path we'll exit any waits for characters to be flushed
from buffers and lose the bytes in some cases ?
You are right. I'll have to change it to use non-interruptible
mutex_lock. I'll prepare a new patch.
Thats why I didn't
convert it - I didn't understand why it was using _interruptible at all ?
No specific reason. just the general rule to prefer sleeping
interuptibly whenever possible, because unkillable processes are
so annoying. Seeing that chars_in_buffer was declared as returning
int, I assumed (wrongly as it now turns out) that it would be
allowed to return the customary negative values for errors, so
that it could use the _interruptible variant. When I saw your
patch I read into it that zero would be the appropriate return
value for all error cases, including a signal while waiting for
the mutex. I guess there was a bit of wishful thinking in that.
Well, thanks again for your help. I'll follow up with a revised
patch.
Regards,
Tilman
--
Tilman Schmidt E-Mail: tilman@imap.cc
Bonn, Germany
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The tty_operation chars_in_buffer() is not allowed to return a
negative value to signal an error. Corrects the problem flagged
by commit 23198fda7182969b619613a555f8645fdc3dc334,
"tty: fix chars_in_buffers".
Impact: error handling bugfix
Signed-off-by: Tilman Schmidt <redacted>
---
drivers/isdn/gigaset/interface.c | 19 +++++++------------
1 files changed, 7 insertions(+), 12 deletions(-)
diff --git a/drivers/isdn/gigaset/interface.c b/drivers/isdn/gigaset/interface.c
index 8ff7e35..f33ac27 100644
--- a/drivers/isdn/gigaset/interface.c
+++ b/drivers/isdn/gigaset/interface.c
@@ -408,33 +408,28 @@ static int if_write_room(struct tty_struct *tty)
return retval;
}
-/* FIXME: This function does not have error returns */
-
static int if_chars_in_buffer(struct tty_struct *tty)
{
struct cardstate *cs;
- int retval = -ENODEV;
+ int retval = 0;
cs = (struct cardstate *) tty->driver_data;
if (!cs) {
pr_err("%s: no cardstate\n", __func__);
- return -ENODEV;
+ return 0;
}
gig_dbg(DEBUG_IF, "%u: %s()", cs->minor_index, __func__);
- if (mutex_lock_interruptible(&cs->mutex))
- return -ERESTARTSYS; // FIXME -EINTR?
+ mutex_lock(&cs->mutex);
- if (!cs->connected) {
+ if (!cs->connected)
gig_dbg(DEBUG_IF, "not connected");
- retval = -ENODEV;
- } else if (!cs->open_count)
+ else if (!cs->open_count)
dev_warn(cs->dev, "%s: device not opened\n", __func__);
- else if (cs->mstate != MS_LOCKED) {
+ else if (cs->mstate != MS_LOCKED)
dev_warn(cs->dev, "can't write to unlocked device\n");
- retval = -EBUSY;
- } else
+ else
retval = cs->ops->chars_in_buffer(cs);
mutex_unlock(&cs->mutex);--
1.6.2.1.214.ge986c