Re: [Xenomai-core] [5/9] Define new syscalls for the posix skin

[Philippe Gerum <rpm@xenomai.org>]

Gilles Chanteperdrix wrote:
> This patch defines the new syscalls get_heap_addr (more on this syscall later),
> and get_thread_cb. The get_thread_cb syscall is used in user-space to associate
> the thread xnthread_t pointer with each user-space xenomai thread, using POSIX
> TSD.
> 
> This is needed for the mutex implementation to allow setting the mutex owner.
> 
> However, two things: 
> - I do not know if you should like that much passing kernel-space pointers to
>   user-space;

We already did that in a few occasions. Let's consider this as an opaque handle
since those values belong to a different address space.

> - this is implemented as a posix skin service, but should probably be defined as
>   a core syscall, and called in all skin implementations, so as to allow threads
>   from other skins to user Xenomai posix skin services.
> 

Since you are doing the initial effort and designing the interface, please move
this to the nucleus directly. If the first implementation only goes through the
POSIX skin, it will likely lower the incentive for other skins to use that
feature, since the amount of work to integrate it will be higher.

> ---
>  include/posix/syscall.h  |    3 +++
>  src/skins/posix/thread.c |   11 +++++++++++
>  2 files changed, 14 insertions(+)
> 
> Index: include/posix/syscall.h
> ===================================================================
> --- include/posix/syscall.h	(revision 3718)
> +++ include/posix/syscall.h	(working copy)
> @@ -46,6 +46,7 @@
>  #define __pse51_mutex_lock            20
>  #define __pse51_mutex_timedlock       21
>  #define __pse51_mutex_trylock         22
> +#define __pse51_check_init            __pse51_mutex_trylock
>  #define __pse51_mutex_unlock          23
>  #define __pse51_cond_init             24
>  #define __pse51_cond_destroy          25
> @@ -101,6 +102,8 @@
>  #define __pse51_thread_getschedparam  75
>  #define __pse51_thread_kill           76
>  #define __pse51_select                77
> +#define __pse51_get_heap_addr         78
> +#define __pse51_get_thread_cb	      79
>  
>  #ifdef __KERNEL__
>  
> Index: src/skins/posix/thread.c
> ===================================================================
> --- src/skins/posix/thread.c	(revision 3718)
> +++ src/skins/posix/thread.c	(working copy)
> @@ -26,6 +26,7 @@
>  #include <posix/syscall.h>
>  
>  extern int __pse51_muxid;
> +extern pthread_key_t pse51_cur_key;
>  
>  static pthread_attr_t default_attr;
>  static int linuxthreads;
> @@ -41,6 +42,13 @@ static void __pthread_sigharden_handler(
>  	XENOMAI_SYSCALL1(__xn_sys_migrate, XENOMAI_XENO_DOMAIN);
>  }
>  
> +static void set_kthread_cb(void)
> +{
> +	void *kthread_cb;
> +	XENOMAI_SKINCALL1(__pse51_muxid, __pse51_get_thread_cb, &kthread_cb);
> +	pthread_setspecific(pse51_cur_key, kthread_cb);
> +}
> +
>  int __wrap_pthread_setschedparam(pthread_t thread,
>  				 int policy, const struct sched_param *param)
>  {
> @@ -56,6 +64,7 @@ int __wrap_pthread_setschedparam(pthread
>  
>  	if (!err && promoted) {
>  		old_sigharden_handler = signal(SIGHARDEN, &__pthread_sigharden_handler);
> +		set_kthread_cb();
>  		if (policy != SCHED_OTHER)
>  			XENOMAI_SYSCALL1(__xn_sys_migrate, XENOMAI_XENO_DOMAIN);
>  	}
> @@ -132,6 +141,8 @@ static void *__pthread_trampoline(void *
>  	start = iargs->start;
>  	cookie = iargs->arg;
>  
> +	set_kthread_cb();
> +
>  	__real_sem_post(&iargs->sync);
>  
>  	if (!err) {
> 
> 


-- 
Philippe.