On Fri, Jul 18, 2014 at 1:35 AM, Hesham Moustafa <heshamelmat...@gmail.com> wrote: > > On Thu, Jul 17, 2014 at 3:10 PM, Joel Sherrill > <joel.sherr...@oarcorp.com> wrote: > > This definitely sounds like not handling the context switch necessary > > part of the > > IRQ processing properly so always returning to IDLE. I call this a > > simple return. > > > > All ports have a version of this code. no_cpu should have reasonable > > pseudo-code. > > m68k is likely the easiest to read as real code. > > > > You need to do a simple return if: > > > > (a) IRQ is nested, or > > (b) DISPATCH_NEEDED is false > > > This is a macro that defines the address of the corresponding variable > within the per cpu config table right? Please correct the following if > I it's wrong. From assembly (when doing restore after C ISR handler is > executed), I have to load this variable value, check if it's true > (greater than zero), and if yes, jump to _ISR_Dispatch. I am a little > confused what context should be loaded in both cases of: simple > return, and _ISR_Dispatch; In case of _ISR_Dispatch, should I save > stack pointer and return address and other context like normal context > switch (function call)? While in interrupt context (simple return), I > am saving almost all registers with some other necessary registers > related to exceptions. > Please see http://rtems.org/onlinedocs/doc-current/share/rtems/html/porting/Interrupts-Interrupt-Dispatching.html#Interrupts-Interrupt-Dispatching
Summarizing: You need to update a few variables before calling the user ISR: _Thread_Dispatch_disable_level += 1 _ISR_Nest_level += 1 And decrement them after returning. If ISRs are nested you do a simple return. Then you need to check if _CPU_ISR_Dispatch_disable is set, if so do a simple return. Then you need to check if DISPATCH_NEEDED, if so you need to do the ISR_Dispatch. > One thing I have a problem with, is when using some macros like > DISPATCH_NEEDED (it's a variable address right?) I am normally > including rtems/score/percpu.h from the assembly file (which does the > magic) to get these definitions but the compiler suffers. I think I > have to provide compiler option or something to just include #define > macros? If yes, where to add it? > Make sure to include rtems/asm.h before including percpu.h so you get the ASM defines instead of C defines, since you are (presumably) writing this in assembly. You could also use inline assembly, but then you need to use expression operands [1] to provide access to these variables instead. [1] https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html -Gedare > > Otherwise, you need to some CPU specific magic to get our of the IRQ and > > back to the thread. Make it look like it called _Thread_Dispatch with > > sufficient saved registers (e.g. callee destroyed). This is usually called > > _ISR_Dispatch. When the call from _ISR_Dispatch to _Thread_Dispatch > > returns, you do the magic needed to return tot he interrupted thread > > (IDLE in this case) as if nothing happened. _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel