linux-kernel - Re: [PATCH v2] rwsem: Support optimistic spinning

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140430080148.GZ11096@twins.programming.kicks-ass.net>
Date:	Wed, 30 Apr 2014 10:01:48 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Davidlohr Bueso <davidlohr@...com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Alex Shi <alex.shi@...aro.org>,
	Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E.McKenney" <paulmck@...ux.vnet.ibm.com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rwsem: Support optimistic spinning

On Mon, Apr 28, 2014 at 03:09:01PM -0700, Davidlohr Bueso wrote:
> @@ -26,6 +27,10 @@ struct rw_semaphore {
>  	long			count;
>  	raw_spinlock_t		wait_lock;
>  	struct list_head	wait_list;
> +#ifdef CONFIG_SMP
> +	struct task_struct	     *owner; /* write owner */
> +	struct optimistic_spin_queue *osq;   /* spinner MCS lock */
> +#endif
>  #ifdef CONFIG_DEBUG_LOCK_ALLOC
>  	struct lockdep_map	dep_map;
>  #endif
> @@ -55,11 +60,21 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
>  # define __RWSEM_DEP_MAP_INIT(lockname)
>  #endif
>  
> +#ifdef CONFIG_SMP
> +#define __RWSEM_INITIALIZER(name)			\
> +	{ RWSEM_UNLOCKED_VALUE,				\
> +	  __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),	\
> +	  LIST_HEAD_INIT((name).wait_list),		\
> +	  NULL, /* owner */				\
> +	  NULL /* mcs lock */                           \
> +	  __RWSEM_DEP_MAP_INIT(name) }
> +#else
>  #define __RWSEM_INITIALIZER(name)			\
>  	{ RWSEM_UNLOCKED_VALUE,				\
>  	  __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),	\
>  	  LIST_HEAD_INIT((name).wait_list)		\
>  	  __RWSEM_DEP_MAP_INIT(name) }
> +#endif

I'm not saying you should change this; but something like:

#ifdef CONFIG_SMP
# define __RWSEM_SMP_INIT(name)	, .owner = NULL, .osq = NULL
#else
# define __RWSEM_SMP_INIT(name)
#endif

#define __RWSEM_INITIALIZER(name)	{			\
	.count = RWSEM_UNLOCKED_VALUE,				\
	.wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),	\
	.wait_list = LIST_HEAD_INIT(name.wait_list)		\
	__RWSEM_SMP_INIT(name)					\
	__RWSEM_DEP_MAP_INIT(name)				\
}

might be more readable in general.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/