From: Davidlohr Bueso <dave@stgolabs.net>
To: eric@anholt.net, wahrenst@gmx.net
Cc: devel@driverdev.osuosl.org, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] staging: vc04_services: replace g_free_fragments_mutex with spinlock
Date: Mon, 28 Oct 2019 08:53:54 -0700 [thread overview]
Message-ID: <20191028155354.s3bgq2wazwlh32km@linux-p48b> (raw)
In-Reply-To: <20191027221530.12080-1-dave@stgolabs.net>
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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next prev parent reply other threads:[~2019-10-28 15:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20191027221530.12080-1-dave@stgolabs.net>
[not found] ` <576df522-f012-9dd1-9dcc-b7e444e82ac6@gmx.net>
2019-10-28 15:21 ` [PATCH] staging: vc04_services: replace g_free_fragments_mutex with spinlock Davidlohr Bueso
2019-10-28 15:37 ` Greg KH
2019-10-28 15:53 ` Davidlohr Bueso [this message]
2019-10-28 16:24 ` Greg KH
2019-10-28 16:35 ` Davidlohr Bueso
2019-10-28 16:59 ` Greg KH
2019-11-01 18:29 ` [PATCH resend] " Davidlohr Bueso
2019-11-02 10:33 ` Stefan Wahren
2019-11-02 10:35 ` Greg KH
2019-10-28 19:08 ` [PATCH] " Dan Carpenter
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