Re: [Xenomai] Philippe Gerum : cobalt/rtdm: leave mode selection to I/O syscall handlers

* Re: [Xenomai] Philippe Gerum : cobalt/rtdm: leave mode selection to I/O syscall handlers
       [not found] <E1bORzl-00034s-19@xenomai.org>
@ 2016-09-16  4:54 ` Jan Kiszka
  2016-09-16  7:28   ` Philippe Gerum
  0 siblings, 1 reply; 3+ messages in thread
From: Jan Kiszka @ 2016-09-16  4:54 UTC (permalink / raw)
  To: xenomai, Philippe Gerum

On 2016-07-16 17:59, git repository hosting wrote:
> Module: xenomai-3
> Branch: wip/dovetail
> Commit: 37f90fb2a9d1d8ad6e120e01c8972817b315baf6
> URL:    http://git.xenomai.org/?p=xenomai-3.git;a=commit;h=37f90fb2a9d1d8ad6e120e01c8972817b315baf6
> 
> Author: Philippe Gerum <rpm@xenomai.org>
> Date:   Thu Jul  7 18:35:47 2016 +0200
> 
> cobalt/rtdm: leave mode selection to I/O syscall handlers
> 
> We don't want requests bearing invalid file descriptors (RTDM-wise) to
> trigger any mode switch, so that RTDM requests on regular fildes can
> be rejected with little overhead.
> 
> Tell the core to hand over mode selection to RTDM I/O syscall
> handlers, which now check the file descriptor prior to triggering any
> mode transition.
> 
> ---
> 
>  kernel/cobalt/posix/io.c        |   10 +--
>  kernel/cobalt/posix/syscall32.c |    4 +-
>  kernel/cobalt/rtdm/fd.c         |  144 +++++++++++++++++++++++----------------
>  3 files changed, 92 insertions(+), 66 deletions(-)
> 
> diff --git a/kernel/cobalt/posix/io.c b/kernel/cobalt/posix/io.c
> index 7110d21..42b7b00 100644
> --- a/kernel/cobalt/posix/io.c
> +++ b/kernel/cobalt/posix/io.c
> @@ -58,25 +58,25 @@ COBALT_SYSCALL(fcntl, current, (int fd, int cmd, int arg))
>  	return rtdm_fd_fcntl(fd, cmd, arg);
>  }
>  
> -COBALT_SYSCALL(ioctl, probing,
> +COBALT_SYSCALL(ioctl, handover,
>  	       (int fd, unsigned int request, void __user *arg))
>  {
>  	return rtdm_fd_ioctl(fd, request, arg);
>  }
>  
> -COBALT_SYSCALL(read, probing,
> +COBALT_SYSCALL(read, handover,
>  	       (int fd, void __user *buf, size_t size))
>  {
>  	return rtdm_fd_read(fd, buf, size);
>  }
>  
> -COBALT_SYSCALL(write, probing,
> +COBALT_SYSCALL(write, handover,
>  	       (int fd, const void __user *buf, size_t size))
>  {
>  	return rtdm_fd_write(fd, buf, size);
>  }
>  
> -COBALT_SYSCALL(recvmsg, probing,
> +COBALT_SYSCALL(recvmsg, handover,
>  	       (int fd, struct user_msghdr __user *umsg, int flags))
>  {
>  	struct user_msghdr m;
> @@ -93,7 +93,7 @@ COBALT_SYSCALL(recvmsg, probing,
>  	return cobalt_copy_to_user(umsg, &m, sizeof(*umsg)) ?: ret;
>  }
>  
> -COBALT_SYSCALL(sendmsg, probing,
> +COBALT_SYSCALL(sendmsg, handover,
>  	       (int fd, struct user_msghdr __user *umsg, int flags))
>  {
>  	struct user_msghdr m;
> diff --git a/kernel/cobalt/posix/syscall32.c b/kernel/cobalt/posix/syscall32.c
> index 0576b37..bc8b9d9 100644
> --- a/kernel/cobalt/posix/syscall32.c
> +++ b/kernel/cobalt/posix/syscall32.c
> @@ -766,7 +766,7 @@ COBALT_SYSCALL32emu(select, nonrestartable,
>  	return err;
>  }
>  
> -COBALT_SYSCALL32emu(recvmsg, probing,
> +COBALT_SYSCALL32emu(recvmsg, handover,
>  		    (int fd, struct compat_msghdr __user *umsg,
>  		     int flags))
>  {
> @@ -784,7 +784,7 @@ COBALT_SYSCALL32emu(recvmsg, probing,
>  	return sys32_put_msghdr(umsg, &m) ?: ret;
>  }
>  
> -COBALT_SYSCALL32emu(sendmsg, probing,
> +COBALT_SYSCALL32emu(sendmsg, handover,
>  		    (int fd, struct compat_msghdr __user *umsg, int flags))
>  {
>  	struct user_msghdr m;
> diff --git a/kernel/cobalt/rtdm/fd.c b/kernel/cobalt/rtdm/fd.c
> index d82cfe4..3381dea 100644
> --- a/kernel/cobalt/rtdm/fd.c
> +++ b/kernel/cobalt/rtdm/fd.c
> @@ -392,6 +392,44 @@ int rtdm_fd_fcntl(int ufd, int cmd, ...)
>  }
>  EXPORT_SYMBOL_GPL(rtdm_fd_fcntl);
>  
> +static struct rtdm_fd *get_fd_fixup_mode(int ufd)
> +{
> +	struct xnthread *thread;
> +	struct rtdm_fd *fd;
> +	
> +	fd = rtdm_fd_get(ufd, 0);
> +	if (IS_ERR(fd))
> +		return fd;
> +
> +	/*
> +	 * Mode is selected according to the following convention:
> +	 *
> +	 * - Cobalt threads must try running the syscall from primary
> +	 * mode as a first attempt, regardless of their scheduling
> +	 * class. The driver handler may ask for demoting the caller
> +	 * to secondary mode by returning -ENOSYS.
> +	 *
> +	 * - Regular threads (i.e. not bound to Cobalt) may only run
> +	 * the syscall from secondary mode.
> +	 */

In case of IOCTLs, we would also have to push the decision one level
further, into the driver. Only in few cases, default would remain this
policy here. Do you already have a suggestion how to do that?

Thanks,
Jan

-- 
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux

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