Messages in this thread | | | Date | Mon, 28 Oct 2019 08:53:54 -0700 | From | Davidlohr Bueso <> | Subject | Re: [PATCH] staging: vc04_services: replace g_free_fragments_mutex with spinlock |
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Cc devel@driverdev.osuosl.org
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@stgolabs.net> >--- >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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