On Mon, Oct 28, 2019 at 08:53:54AM -0700, Davidlohr Bueso wrote: > 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 > > This is obviously not in a format I can apply it in :( _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
