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RENESAS TOOL NEWS on November 16, 2004: RSO-M3T-MR32R_2-041116D
A Note on Using Real-Time OS M3T-MR32R
--On Releasing a Task from the Acceptance or
Call of a Rendezvous--
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Please take note of the following problem in using the M3T-MR32R real-time OS:
- On releasing a task from the acceptance or call of a rendezvous
- Versions Concerned
M3T-MR32R V.3.00 Release 1 through V.3.50 Release 2
- Descriptions
| (1) |
When a task is in a WAIT state for the acceptance or call of a
rendezvous (the case where Condition (4)-(a) satisfied), no rendezvous
is acknowledged even if the task meets the rendezvous condition, or
another task in the READY state with the same priority as the above
task is interpreted as meeting the rendezvous condition and enters a rendezvous.
As a result of the above operations, such a symptom as writing
a message at an incorrect address arises, and the application
program may not run properly. |
| (2) |
When a task is in a WAIT-SUSPEND state for the acceptances or
calls of rendezvous (the case where Condition (4)-(b) satisfied),
the processing of system calls tcal_por, pcal_por, tacp_por,
pacp_por, and fwd_por cannot terminate. |
- Conditions
This problem occurs if the following conditions are all satisfied:
| (1) |
Any of the following system calls is issued:
acp_por, tacp_por, pacp_por, cal_por, tcal_por, pcal_por, and fwd_por |
| (2) |
On the port that is the object of the system call in (1) exists either of the following tasks:
| (a) |
A task waiting for the call of a rendezvous if acp_por, tacp_por, or pacp_por issued |
| (b) |
A task waiting for the acceptance of a rendezvous if cal_por, tcal_por, pcal_por, or fwd_por issued |
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| (3) |
Either of the tasks in (2) is released from the WAIT or WAIT-SUSPEND
state by issuing an irel_wai system call inside the interrupt handler
invoked during the execution of the system call issued in (1). |
| (4) |
The task that is the object of the irel_wai issued in (3) is in
either of the following states:
| (a) | A Waite state for the acceptance or call of a rendezvous |
| (b) | A WAIT-SUSPEND state for the acceptances or calls of rendezvous |
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- Workaround
This problem can be circumvented either of the following ways:
| (1) |
Before and after issuing the system call concerned, disable and enable an interrupt respectively.
Example
-----------------------------------------------------
void task(INT stacd)
{
. . . . . . . . . . . . . . .
/* Disable an interrupt */
asm(" mvfc R0,PSW\n"
" and3 R0,R0,#0xFFBF\n"
" mvtc R0,PSW\n");
ercd = acp_por(&rno,(VP)msg,&size,ID_por2,0x80);
/* Enable the interrupt */
asm(" mvfc R0,PSW\n"
" or3 R0,R0,#0x0040\n"
" mvtc R0,PSW\n");
. . . . . . . . . . . . . . .
}
----------------------------------------------------- |
| (2) |
Perform the following steps to release a task from a WAIT state:
- Issue an ista_tsk system call to invoke the task to release from a WAIT state.
- Issue a rel_wai system call from the invoked task mentioned above.
Example
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void handler(void)
{
. . . . . . . . . . . . . . .
/* Comment out irel_wai, issue ista_tsk to invoke task
to release from WAIT state, and pass ID of
objective task to ista_tsk as startup code */
/* irel_wai( ID_task1 ); */
ista_tsk( ID_DoRelease,(INT)ID_task1 );
. . . . . . . . . . . . . . .
}
void DoRelease(INT tskid)
{
rel_wai(tskid);
}
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- Schedule of Fixing the Problem
We plan to fix this problem in our next release of the product.
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