Use multiple per-offset wait queues instead of one big wait queue per
region.
Signed-off-by: Hugo Lefeuvre
---
Changes in v2:
- dereference the it pointer instead of wait_queue (which is not set
yet) in handle_vsoc_cond_wait()
---
drivers/staging/android/TODO | 4 ---
drivers/staging/android/vsoc.c | 56 ++
2 files changed, 44 insertions(+), 16 deletions(-)
diff --git a/drivers/staging/android/TODO b/drivers/staging/android/TODO
index fbf015cc6d62..cd2af06341dc 100644
--- a/drivers/staging/android/TODO
+++ b/drivers/staging/android/TODO
@@ -12,10 +12,6 @@ ion/
- Better test framework (integration with VGEM was suggested)
vsoc.c, uapi/vsoc_shm.h
- - The current driver uses the same wait queue for all of the futexes in a
- region. This will cause false wakeups in regions with a large number of
- waiting threads. We should eventually use multiple queues and select the
- queue based on the region.
- Add debugfs support for examining the permissions of regions.
- Remove VSOC_WAIT_FOR_INCOMING_INTERRUPT ioctl. This functionality has been
superseded by the futex and is there for legacy reasons.
diff --git a/drivers/staging/android/vsoc.c b/drivers/staging/android/vsoc.c
index f2bb18158e5b..97303d9173aa 100644
--- a/drivers/staging/android/vsoc.c
+++ b/drivers/staging/android/vsoc.c
@@ -31,6 +31,7 @@
#include
#include
#include
+#include
#include "uapi/vsoc_shm.h"
#define VSOC_DEV_NAME "vsoc"
@@ -62,11 +63,18 @@ static const int MAX_REGISTER_BAR_LEN = 0x100;
*/
static const int SHARED_MEMORY_BAR = 2;
+struct vsoc_futex_wait_queue_t {
+ struct list_head list;
+ u32 offset;
+ wait_queue_head_t queue;
+};
+
struct vsoc_region_data {
char name[VSOC_DEVICE_NAME_SZ + 1];
wait_queue_head_t interrupt_wait_queue;
- /* TODO(b/73664181): Use multiple futex wait queues */
- wait_queue_head_t futex_wait_queue;
+ /* Per-offset futex wait queue. */
+ struct list_head futex_wait_queue_list;
+ spinlock_t futex_wait_queue_lock;
/* Flag indicating that an interrupt has been signalled by the host. */
atomic_t *incoming_signalled;
/* Flag indicating the guest has signalled the host. */
@@ -402,6 +410,7 @@ static int handle_vsoc_cond_wait(struct file *filp, struct
vsoc_cond_wait *arg)
struct vsoc_region_data *data = vsoc_dev.regions_data + region_number;
int ret = 0;
struct vsoc_device_region *region_p = vsoc_region_from_filep(filp);
+ struct vsoc_futex_wait_queue_t *it, *wait_queue = NULL;
atomic_t *address = NULL;
ktime_t wake_time;
@@ -415,10 +424,27 @@ static int handle_vsoc_cond_wait(struct file *filp,
struct vsoc_cond_wait *arg)
address = shm_off_to_virtual_addr(region_p->region_begin_offset +
arg->offset);
+ /* Find wait queue corresponding to offset or create it */
+ spin_lock(>futex_wait_queue_lock);
+ list_for_each_entry(it, >futex_wait_queue_list, list) {
+ if (it->offset == arg->offset) {
+ wait_queue = it;
+ break;
+ }
+ }
+
+ if (!wait_queue) {
+ wait_queue = kmalloc(sizeof(*wait_queue), GFP_KERNEL);
+ wait_queue->offset = arg->offset;
+ init_waitqueue_head(_queue->queue);
+ list_add(_queue->list, >futex_wait_queue_list);
+ }
+ spin_unlock(>futex_wait_queue_lock);
+
/* Ensure that the type of wait is valid */
switch (arg->wait_type) {
case VSOC_WAIT_IF_EQUAL:
- ret = wait_event_freezable(data->futex_wait_queue,
+ ret = wait_event_freezable(wait_queue->queue,
arg->wakes++ &&
atomic_read(address) != arg->value);
break;
@@ -426,7 +452,7 @@ static int handle_vsoc_cond_wait(struct file *filp, struct
vsoc_cond_wait *arg)
if (arg->wake_time_nsec >= NSEC_PER_SEC)
return -EINVAL;
wake_time = ktime_set(arg->wake_time_sec, arg->wake_time_nsec);
- ret = wait_event_freezable_hrtimeout(data->futex_wait_queue,
+ ret = wait_event_freezable_hrtimeout(wait_queue->queue,
arg->wakes++ &&
atomic_read(address) !=
arg->value,
wake_time);
@@ -463,6 +489,7 @@ static int do_vsoc_cond_wake(struct file *filp, uint32_t
offset)
struct vsoc_device_region *region_p = vsoc_region_from_filep(filp);
u32 region_number = iminor(file_inode(filp));
struct vsoc_region_data *data = vsoc_dev.regions_data + region_number;
+ struct vsoc_futex_wait_queue_t *wait_queue;
/* Ensure that the offset is
