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authorLars-Peter Clausen <lars@metafoo.de>2013-07-16 15:28:00 +0100
committerJonathan Cameron <jic23@kernel.org>2013-07-20 10:18:53 +0100
commita1a8e1dc111d6f05e7164e851e58219d428359e1 (patch)
treecc55f2ba12e095a29599bb7f0084dc905c82d8b1 /drivers/iio/industrialio-trigger.c
parent78077256bc08348d587e318957ceb41fe4d4afae (diff)
downloadlinux-a1a8e1dc111d6f05e7164e851e58219d428359e1.tar.gz
iio:trigger: Fix use_count race condition
When using more than one trigger consumer it can happen that multiple threads perform a read-modify-update cycle on 'use_count' concurrently. This can cause updates to be lost and use_count can get stuck at non-zero value, in which case the IIO core assumes that at least one thread is still running and will wait for it to finish before running any trigger handlers again. This effectively renders the trigger disabled and a reboot is necessary before it can be used again. To fix this make use_count an atomic variable. Also set it to the number of consumers before starting the first consumer, otherwise it might happen that use_count drops to 0 even though not all consumers have been run yet. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Tested-by: Denis Ciocca <denis.ciocca@st.com> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Diffstat (limited to 'drivers/iio/industrialio-trigger.c')
-rw-r--r--drivers/iio/industrialio-trigger.c34
1 files changed, 22 insertions, 12 deletions
diff --git a/drivers/iio/industrialio-trigger.c b/drivers/iio/industrialio-trigger.c
index ea8a4146620d..0dd9bb873130 100644
--- a/drivers/iio/industrialio-trigger.c
+++ b/drivers/iio/industrialio-trigger.c
@@ -127,12 +127,17 @@ static struct iio_trigger *iio_trigger_find_by_name(const char *name,
void iio_trigger_poll(struct iio_trigger *trig, s64 time)
{
int i;
- if (!trig->use_count)
- for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++)
- if (trig->subirqs[i].enabled) {
- trig->use_count++;
+
+ if (!atomic_read(&trig->use_count)) {
+ atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
+
+ for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) {
+ if (trig->subirqs[i].enabled)
generic_handle_irq(trig->subirq_base + i);
- }
+ else
+ iio_trigger_notify_done(trig);
+ }
+ }
}
EXPORT_SYMBOL(iio_trigger_poll);
@@ -146,19 +151,24 @@ EXPORT_SYMBOL(iio_trigger_generic_data_rdy_poll);
void iio_trigger_poll_chained(struct iio_trigger *trig, s64 time)
{
int i;
- if (!trig->use_count)
- for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++)
- if (trig->subirqs[i].enabled) {
- trig->use_count++;
+
+ if (!atomic_read(&trig->use_count)) {
+ atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
+
+ for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) {
+ if (trig->subirqs[i].enabled)
handle_nested_irq(trig->subirq_base + i);
- }
+ else
+ iio_trigger_notify_done(trig);
+ }
+ }
}
EXPORT_SYMBOL(iio_trigger_poll_chained);
void iio_trigger_notify_done(struct iio_trigger *trig)
{
- trig->use_count--;
- if (trig->use_count == 0 && trig->ops && trig->ops->try_reenable)
+ if (atomic_dec_and_test(&trig->use_count) && trig->ops &&
+ trig->ops->try_reenable)
if (trig->ops->try_reenable(trig))
/* Missed an interrupt so launch new poll now */
iio_trigger_poll(trig, 0);