From: Greg KH <gregkh@linuxfoundation.org>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: valdis.kletnieks@vt.edu, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drivers/staging/exfat: Replace binary semaphores for mutexes
Date: Tue, 29 Oct 2019 09:05:21 +0100 [thread overview]
Message-ID: <20191029080521.GA494993@kroah.com> (raw)
In-Reply-To: <20191028024519.32344-1-dave@stgolabs.net>
On Sun, Oct 27, 2019 at 07:45:19PM -0700, Davidlohr Bueso wrote:
> 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.
> There is also lockdep support.
>
> For both v_sem and z_sem, their semantics imply traditional lock
> ownership; that is, the lock owner is the same for both lock/unlock
> operations and nothing is done in irq context. Therefore it is safe
> to convert.
>
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> ---
> This is part of further reducing semaphore users in the kernel.
>
> drivers/staging/exfat/exfat.h | 2 +-
> drivers/staging/exfat/exfat_super.c | 84 ++++++++++++++++++-------------------
> 2 files changed, 43 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/staging/exfat/exfat.h b/drivers/staging/exfat/exfat.h
> index 6c12f2d79f4d..95c02f55de60 100644
> --- a/drivers/staging/exfat/exfat.h
> +++ b/drivers/staging/exfat/exfat.h
> @@ -618,7 +618,7 @@ struct fs_info_t {
> u32 dev_ejected; /* block device operation error flag */
>
> struct fs_func *fs_func;
> - struct semaphore v_sem;
> + struct mutex v_mutex;
>
> /* FAT cache */
> struct buf_cache_t FAT_cache_array[FAT_CACHE_SIZE];
> diff --git a/drivers/staging/exfat/exfat_super.c b/drivers/staging/exfat/exfat_super.c
> index 5f6caee819a6..c0b09b2dbe96 100644
> --- a/drivers/staging/exfat/exfat_super.c
> +++ b/drivers/staging/exfat/exfat_super.c
> @@ -283,7 +283,7 @@ static const struct dentry_operations exfat_dentry_ops = {
> .d_compare = exfat_cmp,
> };
>
> -static DEFINE_SEMAPHORE(z_sem);
> +static DEFINE_MUTEX(z_mutex);
>
> static inline void fs_sync(struct super_block *sb, bool do_sync)
> {
> @@ -352,11 +352,11 @@ static int ffsMountVol(struct super_block *sb)
>
> pr_info("[EXFAT] trying to mount...\n");
>
> - down(&z_sem);
> + mutex_lock(&z_mutex);
No tabs? :(
next prev parent reply other threads:[~2019-10-29 8:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-28 2:45 [PATCH] drivers/staging/exfat: Replace binary semaphores for mutexes Davidlohr Bueso
2019-10-29 8:05 ` Greg KH [this message]
2019-10-30 14:49 ` [PATCH v2] " Davidlohr Bueso
2019-10-30 15:40 ` Valdis Klētnieks
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