Cc devel@xxxxxxxxxxxxxxxxxxxx On Sun, 27 Oct 2019, Bueso wrote:
There seems no need to be using a semaphore, or a sleeping lock in the first place: critical region is extremely short, does not call into any blocking calls and furthermore lock and unlocking operations occur in the same context. Get rid of another semaphore user by replacing it with a spinlock. Signed-off-by: Davidlohr Bueso <dave@xxxxxxxxxxxx> --- This is in an effort to further reduce semaphore users in the kernel. .../staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c index 8dc730cfe7a6..710d21654128 100644 --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c @@ -63,7 +63,7 @@ static char *g_free_fragments; static struct semaphore g_free_fragments_sema; static struct device *g_dev; -static DEFINE_SEMAPHORE(g_free_fragments_mutex); +static DEFINE_SPINLOCK(g_free_fragments_lock); static irqreturn_t vchiq_doorbell_irq(int irq, void *dev_id); @@ -528,11 +528,11 @@ create_pagelist(char __user *buf, size_t count, unsigned short type) WARN_ON(g_free_fragments == NULL); - down(&g_free_fragments_mutex); + spin_lock(&g_free_fragments_lock); fragments = g_free_fragments; WARN_ON(fragments == NULL); g_free_fragments = *(char **) g_free_fragments; - up(&g_free_fragments_mutex); + spin_unlock(&g_free_fragments_lock); pagelist->type = PAGELIST_READ_WITH_FRAGMENTS + (fragments - g_fragments_base) / g_fragments_size; } @@ -591,10 +591,10 @@ free_pagelist(struct vchiq_pagelist_info *pagelistinfo, kunmap(pages[num_pages - 1]); } - down(&g_free_fragments_mutex); + spin_lock(&g_free_fragments_lock); *(char **)fragments = g_free_fragments; g_free_fragments = fragments; - up(&g_free_fragments_mutex); + spin_unlock(&g_free_fragments_lock); up(&g_free_fragments_sema); } -- 2.16.4
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