Re: tasklet latency and system calls on mips

["Sirotkin, Alexander" <demiurg@ti.com>]

Jun Sun wrote:

On Thu, Aug 14, 2003 at 12:17:52PM +0300, Sirotkin, Alexander wrote:
  

I suspect that what happens is as follows :

system call arrives and while it's being processed and interrupt to one
of the drivers arrives. This interrupt 
schedules a tasklet which however is not executed after the system call
finishes, 
    

The tasklet should be executed at the return of interrupt handling.
If not, there is a bug.
  

I have a feeling that we are going in circles. Tasklets are executed at the return of interrupt handler.
However, I suspect that this is not enough. On mips (contrary to x86), system call is NOT an interrupt.
It's a different exception with different handler. Therefore I suspect that tasklets are NOT called at
the end of system call exception handler (which is a different handler, not do_IRQ).

only after the next timer
interrupt which causes up to 10 ms latency (not all the time, only when
somebody makes a system call).

    

BTW, make sure tasklet_schedule() is indeed called in an interrupt handler.
I am not sure why will happen otherwise.

If you suspect it is a bug, you can easily trace them.  You may my
little tracing tool useful,

I can try to trace it, I just wanted to ensure that what I was saying makes sense. See above.

	http://linux.junsun.net/patches/generic/experimental/030716.a-jstrace.patch

Jun
  

-- 
Alexander Sirotkin
SW Engineer

Texas Instruments
Broadband Communications Israel (BCIL)
Tel:  +972-9-9706587
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