Hi I am using STR9 I have to interface it with clrc632 chip that is 14443 based RFID chip previously I have written the driver for the same using linux 2.6 kernel there was an approach in which we devide the lenthy interrupt routene to TOP half and Bottom half now I have to execute 5 tasks in the RTX I want to make the scheduling like that of linux my problem is how to perform lenthy process in interrupt handler is there need of top half and bottom half in kiel?
If you are forbidding RTX from switching tasks, then you no longer have an RTOS.
Take a closer look at your code. You can most probably rewrite the code so that it becomes friendlier. The task should work with its own private data structures (which means that a task switch will not allow any other task to see inconsistent data structures) and when done, just flip a flag or similar to publish the work and then start on the next iteration using a second set of variables.
The communication with the modem is serial, so you just push the data into a send queue and let the interrupt send and receive. Your task gets activated when you have received data to process.
And unless you are using a multiplexer (like the GSM 07.10 standard) you should have only one task that is communicating with the modem at any one time. When one task is done, it can of course release the modem to another task.