Date: Wed, 4 Aug 2010 13:10:33 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Jeff Roberson <jeff@FreeBSD.org> Cc: svn-src-projects@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r210790 - projects/ofed/head/sys/ofed/include/linux Message-ID: <alpine.BSF.2.00.1008041309300.25854@fledge.watson.org> In-Reply-To: <201008030838.o738cQaS090469@svn.freebsd.org> References: <201008030838.o738cQaS090469@svn.freebsd.org>
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On Tue, 3 Aug 2010, Jeff Roberson wrote:
> - Convert the linux semaphores to use BSD sempahores rather than sx locks.
> There are places where we need counting semaphore semantics. This is
> unfortunate since sema(9) is not implemented with the most expedient
> possible mechanism.
sema(9) also has near-zero consumers in the tree, hence a lack of optimization
focus, etc. In many ways it would be nice to make it go away simply to narrow
the menu on synchronization primitives a bit. Of course, that would mean not
introducing new consumers... :-)
Robert
>
> Sponsored by: Isilon Systems, iX Systems, and Panasas.
>
> Modified:
> projects/ofed/head/sys/ofed/include/linux/semaphore.h
>
> Modified: projects/ofed/head/sys/ofed/include/linux/semaphore.h
> ==============================================================================
> --- projects/ofed/head/sys/ofed/include/linux/semaphore.h Tue Aug 3 08:37:16 2010 (r210789)
> +++ projects/ofed/head/sys/ofed/include/linux/semaphore.h Tue Aug 3 08:38:25 2010 (r210790)
> @@ -30,25 +30,35 @@
>
> #include <sys/param.h>
> #include <sys/lock.h>
> -#include <sys/sx.h>
> +#include <sys/sema.h>
>
> +/*
> + * XXX BSD semaphores are disused and slow. They also do not provide a
> + * sema_wait_sig method. This must be resolved eventually.
> + */
> struct semaphore {
> - struct sx sx;
> + struct sema sema;
> };
>
> -#define init_MUTEX(_rw) sx_init_flags(&(_rw)->sx, \
> - "lnxsema", SX_NOWITNESS)
> -#define down(_rw) sx_xlock(&(_rw)->sx)
> -#define down_interruptible(_rw) sx_xlock_sig(&(_rw)->sx)
> -#define down_trylock(_rw) !sx_try_xlock(&(_rw)->sx)
> -#define up(_rw) sx_xunlock(&(_rw)->sx)
> +#define down(_sem) sema_wait(&(_sem)->sema)
> +#define down_interruptible(_sem) sema_wait(&(_sem)->sema), 0
> +#define down_trylock(_sem) !sema_trywait(&(_sem)->sema)
> +#define up(_sem) sema_post(&(_sem)->sema)
>
> static inline void
> -sema_init(struct semaphore *sem, int val)
> +linux_sema_init(struct semaphore *sem, int val)
> {
> - init_MUTEX(sem);
> - if (val == 0)
> - down(sem);
> +
> + sema_init(&sem->sema, val, "lnxsema");
> }
>
> +static inline void
> +init_MUTEX(struct semaphore *sem)
> +{
> +
> + sema_init(&sem->sema, 1, "lnxsema");
> +}
> +
> +#define sema_init linux_sema_init
> +
> #endif /* _LINUX_SEMAPHORE_H_ */
>
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