On Fri, Jul 18, 2014 at 4:15 PM, Hesham Moustafa <heshamelmat...@gmail.com> wrote:
> On Fri, Jul 18, 2014 at 4:17 PM, Gedare Bloom <ged...@rtems.org> wrote: > > 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 > > > Yes, I have read this along with no_cpu.h, m68k, nios2 code. > > 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. > > > That's what I try to do in assembly, but still I get a compilation error > when > including the headers containing DISPATCH_NEEDED macros and other > nesting and dispatch disable macros. The files included in my assembly > file exactly the same as m68k. Please have a look I just pushed for anyone > to review, but it still produce compilation error for no recognizing C > code. > > What is the compilation error? Is it only DISPATCH_NEEDED, or also ISR_NEST_LEVEL and THREAD_DISPATCH_DISABLE_LEVEL? Do you have the correct define for SYM() in your asm.h? [1] > https://github.com/heshamelmatary/rtems-gsoc2014/blob/or1k/cpukit/score/cpu/or1k/or1k-exception-handler-low.S > > > >> 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. >
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