| Message ID | 20200312112517.GA32485@syed (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,1/3] counter: 104-quad-8: Add lock guards - generic interface | expand |
On Thu, Mar 12, 2020 at 04:55:17PM +0530, Syed Nayyar Waris wrote: > Add lock protection from race conditions in the 104-quad-8 counter > driver for differential encoder cable status changes. There is no IRQ > handling so spin_lock calls are used for protection. > > Fixes: bbef69e088c3 ("counter: 104-quad-8: Support Differential Encoder > Cable Status") > > Signed-off-by: Syed Nayyar Waris <syednwaris@gmail.com> > > Split the patch from generic driver interface and clock prescaler > related code changes. Also, include more code statements for protection > using spin_lock calls and remove protection from few code statements as > they are unnecessary. > --- Hello Syed, Just like in the first patch, move these comments below the "---" line. > drivers/counter/104-quad-8.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c > index 9dab190..1ce9660 100644 > --- a/drivers/counter/104-quad-8.c > +++ b/drivers/counter/104-quad-8.c > @@ -1153,16 +1153,22 @@ static ssize_t quad8_signal_cable_fault_read(struct counter_device *counter, > { > const struct quad8_iio *const priv = counter->priv; > const size_t channel_id = signal->id / 2; > - const bool disabled = !(priv->cable_fault_enable & BIT(channel_id)); > + bool disabled; > unsigned int status; > unsigned int fault; > > + spin_lock(&((struct quad8_iio *)priv)->lock); You can redeclare priv whenever you need to avoid these casts: struct quad8_iio *const priv = counter->priv; ... spin_lock(&priv->lock); ... spin_unlock(&priv->lock); > + > + disabled = !(priv->cable_fault_enable & BIT(channel_id)); > + > if (disabled) > return -EINVAL; This return statement can cause a deadlock. You can avoid that by calling spin_unlock before the return: if (disabled) { spin_unlock(&priv->lock); return -EINVAL; } Sincerely, William Breathitt Gray > > /* Logic 0 = cable fault */ > status = inb(priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS); > > + spin_unlock(&((struct quad8_iio *)priv)->lock); > + > /* Mask respective channel and invert logic */ > fault = !(status & BIT(channel_id)); > > @@ -1194,6 +1200,8 @@ static ssize_t quad8_signal_cable_fault_enable_write( > if (ret) > return ret; > > + spin_lock(&priv->lock); > + > if (enable) > priv->cable_fault_enable |= BIT(channel_id); > else > @@ -1204,6 +1212,8 @@ static ssize_t quad8_signal_cable_fault_enable_write( > > outb(cable_fault_enable, priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS); > > + spin_unlock(&priv->lock); > + > return len; > } > > -- > 2.7.4 >
diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c index 9dab190..1ce9660 100644 --- a/drivers/counter/104-quad-8.c +++ b/drivers/counter/104-quad-8.c @@ -1153,16 +1153,22 @@ static ssize_t quad8_signal_cable_fault_read(struct counter_device *counter, { const struct quad8_iio *const priv = counter->priv; const size_t channel_id = signal->id / 2; - const bool disabled = !(priv->cable_fault_enable & BIT(channel_id)); + bool disabled; unsigned int status; unsigned int fault; + spin_lock(&((struct quad8_iio *)priv)->lock); + + disabled = !(priv->cable_fault_enable & BIT(channel_id)); + if (disabled) return -EINVAL; /* Logic 0 = cable fault */ status = inb(priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS); + spin_unlock(&((struct quad8_iio *)priv)->lock); + /* Mask respective channel and invert logic */ fault = !(status & BIT(channel_id)); @@ -1194,6 +1200,8 @@ static ssize_t quad8_signal_cable_fault_enable_write( if (ret) return ret; + spin_lock(&priv->lock); + if (enable) priv->cable_fault_enable |= BIT(channel_id); else @@ -1204,6 +1212,8 @@ static ssize_t quad8_signal_cable_fault_enable_write( outb(cable_fault_enable, priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS); + spin_unlock(&priv->lock); + return len; }
Add lock protection from race conditions in the 104-quad-8 counter driver for differential encoder cable status changes. There is no IRQ handling so spin_lock calls are used for protection. Fixes: bbef69e088c3 ("counter: 104-quad-8: Support Differential Encoder Cable Status") Signed-off-by: Syed Nayyar Waris <syednwaris@gmail.com> Split the patch from generic driver interface and clock prescaler related code changes. Also, include more code statements for protection using spin_lock calls and remove protection from few code statements as they are unnecessary. --- drivers/counter/104-quad-8.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)