Re: Critical section - pSOS+

Hi Jerry,
Thanks for your reply.
   I have the splx() routine given from pSOS+, I am also having the
wrapper code which calls the psos 's system call to disable the
preemption of the task. I can do this successfully. But My problem is,
how can i implement the interrupts enabling/disabling mechanism at the
task level.

 Present mechanism has got a loophole: whenever we disable interrupts any
other task enables it. I want to have a mechanism, which is there UNIX.
something like splnet,splclock,splhigh,splimp,splx, at each task level.

any suggestions...
-Srini...



On Thu, 4 Jan 2001, Jerry Van Baren wrote:

I forgot if splx() returns the current value of the interrupt enable
bit.  If it doesn't, modify it to do so.  If I recall correctly, the
routine is in the BSP (been a little while since I messed with PPC
pSOS).  If I recall wrongly, you may need to write your own version of
splx(), naming it something else to avoid name collisions, and use it
instead of the provided splx().

Once your splx() routine returns the current value of the EE flag, save
it in a variable, and restore the value when you exit your critical region.

Something like...

void foo()
{
     int ee;

     ee = splix(1);      /* mask interrupts */
     bar()
     splx(ee);           /* restore the interrupt level */
}

gvb


At 09:37 AM 1/4/01 +0530, Srinivas Rao.M wrote:

quoted

Hi to all,

 I am sorry, This question is not releated to the list directly.

 We have a custom board built using MPC860 processor and running the
pSOS+ kernel. We are running a multitasking application on this. we are
facing a problem with the critical section.
we have in pSOS+, splx(1) and splx(0) calls for disabling and enabling the
interrupts respectively. Having multiple tasks running on the kernel,
suppose if one task disables the interrupt by calling splx(1),
The other task can enable the interrupts back to the old posture by
calling splx(0). Hence the critical section code is left in the non
critical section area. Unlike UNIX, pSOS+ doesnot provide, the interrupts
locking (and unlocking) mechanism at the task level.
In such contexts how can we solve this problem.

Thanks in advance.
Srini...

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