| Message ID | 20210921103346.64824-2-tony@atomide.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Get rid of pm_runtime_irq_safe() for 8250_omap | expand |
On Tue, Sep 21, 2021 at 1:34 PM Tony Lindgren <tony@atomide.com> wrote: > > We check for -EAGAIN in n_tty_write() but never currently get it from > process_output_block(). Let's add -EAGAIN handling and break out with 0 > bytes processed. Note that if we return -EAGAIN from n_tty_write(), it > will be treated as error by the caller rather than a retry. > > Looking at the patch description for commit 9ef8927f45f2 ("n_tty: check > for negative and zero space return from tty_write_room") it looks like we > have not made use of -EGAIN from process_output_block() so far, so this -EGAIN? > does not seem like it's currently needed as a fix. > > We can use -EAGAIN for serial layer power management changes as we now > will make use of write_room() returning 0 for an idled serial port. > > Signed-off-by: Tony Lindgren <tony@atomide.com> > --- > drivers/tty/n_tty.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c > --- a/drivers/tty/n_tty.c > +++ b/drivers/tty/n_tty.c > @@ -549,6 +549,8 @@ static ssize_t process_output_block(struct tty_struct *tty, > space = tty_write_room(tty); > if (space <= 0) { > mutex_unlock(&ldata->output_lock); > + if (!space) > + space = -EAGAIN; > return space; > } > if (nr > space) > @@ -2287,8 +2289,10 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, > while (nr > 0) { > ssize_t num = process_output_block(tty, b, nr); > if (num < 0) { > - if (num == -EAGAIN) > - break; > + if (num == -EAGAIN) { > + retval = 0; > + goto break_out; > + } > retval = num; > goto break_out; > } > -- > 2.33.0
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -549,6 +549,8 @@ static ssize_t process_output_block(struct tty_struct *tty, space = tty_write_room(tty); if (space <= 0) { mutex_unlock(&ldata->output_lock); + if (!space) + space = -EAGAIN; return space; } if (nr > space) @@ -2287,8 +2289,10 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, while (nr > 0) { ssize_t num = process_output_block(tty, b, nr); if (num < 0) { - if (num == -EAGAIN) - break; + if (num == -EAGAIN) { + retval = 0; + goto break_out; + } retval = num; goto break_out; }
We check for -EAGAIN in n_tty_write() but never currently get it from process_output_block(). Let's add -EAGAIN handling and break out with 0 bytes processed. Note that if we return -EAGAIN from n_tty_write(), it will be treated as error by the caller rather than a retry. Looking at the patch description for commit 9ef8927f45f2 ("n_tty: check for negative and zero space return from tty_write_room") it looks like we have not made use of -EGAIN from process_output_block() so far, so this does not seem like it's currently needed as a fix. We can use -EAGAIN for serial layer power management changes as we now will make use of write_room() returning 0 for an idled serial port. Signed-off-by: Tony Lindgren <tony@atomide.com> --- drivers/tty/n_tty.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)