[PATCH 5.4 014/154] drivers/hv: Replace binary semaphore with mutex

Greg Kroah-Hartman
2025-04-08T12:02:49Z

From: Davidlohr Bueso <dave@stgolabs.net>

[ Upstream commit 8aea7f82153d6f292add3eb4bd7ba8edcae5c7f7 ]

At a slight footprint cost (24 vs 32 bytes), mutexes are more optimal
than semaphores; it's also a nicer interface for mutual exclusion,
which is why they are encouraged over binary semaphores, when possible.

Replace the hyperv_mmio_lock, its semantics implies traditional lock
ownership; that is, the lock owner is the same for both lock/unlock
operations. Therefore it is safe to convert.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Stable-dep-of: 73fe9073c0cc ("Drivers: hv: vmbus: Don't release fb_mmio resource in vmbus_free_mmio()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/hv/vmbus_drv.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 01a2eeb2ec961..488ea7810ad99 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -107,7 +107,7 @@ static struct notifier_block hyperv_panic_block = {
static const char *fb_mmio_name = "fb_range";
static struct resource *fb_mmio;
static struct resource *hyperv_mmio;
-static DEFINE_SEMAPHORE(hyperv_mmio_lock);
+static DEFINE_MUTEX(hyperv_mmio_lock);

static int vmbus_exists(void)
{
@@ -2082,7 +2082,7 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
int retval;

retval = -ENXIO;
- down(&hyperv_mmio_lock);
+ mutex_lock(&hyperv_mmio_lock);

/*
* If overlaps with frame buffers are allowed, then first attempt to
@@ -2137,7 +2137,7 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
}

exit:
- up(&hyperv_mmio_lock);
+ mutex_unlock(&hyperv_mmio_lock);
return retval;
}
EXPORT_SYMBOL_GPL(vmbus_allocate_mmio);
@@ -2154,7 +2154,7 @@ void vmbus_free_mmio(resource_size_t start, resource_size_t size)
{
struct resource *iter;

- down(&hyperv_mmio_lock);
+ mutex_lock(&hyperv_mmio_lock);
for (iter = hyperv_mmio; iter; iter = iter->sibling) {
if ((iter->start >= start + size) || (iter->end <= start))
continue;
@@ -2162,7 +2162,7 @@ void vmbus_free_mmio(resource_size_t start, resource_size_t size)
__release_region(iter, start, size);
}
release_mem_region(start, size);
- up(&hyperv_mmio_lock);
+ mutex_unlock(&hyperv_mmio_lock);

}
EXPORT_SYMBOL_GPL(vmbus_free_mmio);
--
2.39.5