[ECOS] why is it wrong to call cyg_semaphore_post() in ISR???

["Monica Dsz" <monica.dsz@googlemail.com>]

Hallo all,

I am new to eCos(and also to embedded). The eCos documentation says that ISR 
should not involve any kernel calls.But I want to know why 
cyg_semaphore_post() is not allowed in ISR(Interrupt service routine). It 
doesnt block. and i tried to use it though documentation says we shouldnt. 
It worked for me with the following code.

cyg_uint32 timer_isr(cyg_vector_t vector,cyg_addrword_t data)
{
  led_toggle();                    //Toggle the LED

  isr_counter++;                //32 bit ISR counter

  cyg_interrupt_acknowledge( vector ); //acknowledge the Interrupt to the 
processor

  cyg_semaphore_post( &intr_occured );   //give the semaphore,so that task 
waiting for it wakes up

  return( CYG_ISR_HANDLED  );          // Inform the kernel that ISR is 
handled
}

I wonder why in eCos,a semaphore cannot be posted in ISR. In VxWorks we can 
give a semaphore in ISR. Can anybody give me a pointer to documentation or 
an explanation for this.

Thank you in advance

monica


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