[PATCH] score: Add _CPU_Context_switch_no_return()
Joel Sherrill
joel.sherrill at gmail.com
Mon May 17 22:07:18 UTC 2021
Does this impact the porting guide or any CPU supplement?
On Mon, May 17, 2021 at 4:42 PM Gedare Bloom <gedare at rtems.org> wrote:
> ok to me
>
> On Mon, May 17, 2021 at 5:43 AM Sebastian Huber
> <sebastian.huber at embedded-brains.de> wrote:
> >
> > The __builtin_unreachable() cannot be used with current GCC versions to
> > tell the compiler that a function does not return to the caller, see:
> >
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99151
> >
> > Add a no return variant of _CPU_Context_switch() to avoid generation of
> > dead code in _Thread_Start_multitasking() if RTEMS was built with SMP
> > support enabled.
> > ---
> > bsps/powerpc/shared/cpu_asm.S | 2 ++
> > cpukit/score/cpu/arm/cpu_asm.S | 3 ++
> > .../score/cpu/arm/include/rtems/score/cpu.h | 5 ++++
> > .../cpu/no_cpu/include/rtems/score/cpu.h | 30 +++++++++++++++++--
> > .../cpu/powerpc/include/rtems/score/cpu.h | 5 ++++
> > .../score/cpu/riscv/include/rtems/score/cpu.h | 5 ++++
> > cpukit/score/cpu/riscv/riscv-context-switch.S | 2 ++
> > cpukit/score/cpu/sparc/cpu_asm.S | 2 ++
> > .../score/cpu/sparc/include/rtems/score/cpu.h | 5 ++++
> > cpukit/score/src/threadstartmultitasking.c | 2 +-
> > 10 files changed, 57 insertions(+), 4 deletions(-)
> >
> > diff --git a/bsps/powerpc/shared/cpu_asm.S
> b/bsps/powerpc/shared/cpu_asm.S
> > index e4d627016c..63f6a3fdfe 100644
> > --- a/bsps/powerpc/shared/cpu_asm.S
> > +++ b/bsps/powerpc/shared/cpu_asm.S
> > @@ -258,7 +258,9 @@ PROC (_CPU_Context_restore_fp):
> >
> > ALIGN (PPC_CACHE_ALIGNMENT, PPC_CACHE_ALIGN_POWER)
> > PUBLIC_PROC (_CPU_Context_switch)
> > + PUBLIC_PROC (_CPU_Context_switch_no_return)
> > PROC (_CPU_Context_switch):
> > +PROC (_CPU_Context_switch_no_return):
> >
> > #ifdef BSP_USE_SYNC_IN_CONTEXT_SWITCH
> > sync
> > diff --git a/cpukit/score/cpu/arm/cpu_asm.S
> b/cpukit/score/cpu/arm/cpu_asm.S
> > index 66f8ba6032..46eb46b914 100644
> > --- a/cpukit/score/cpu/arm/cpu_asm.S
> > +++ b/cpukit/score/cpu/arm/cpu_asm.S
> > @@ -54,6 +54,9 @@
> > */
> >
> > DEFINE_FUNCTION_ARM(_CPU_Context_switch)
> > + .globl _CPU_Context_switch_no_return
> > + .set _CPU_Context_switch_no_return, _CPU_Context_switch
> > +
> > /* Start saving context */
> > GET_SELF_CPU_CONTROL r2
> > ldr r3, [r2, #PER_CPU_ISR_DISPATCH_DISABLE]
> > diff --git a/cpukit/score/cpu/arm/include/rtems/score/cpu.h
> b/cpukit/score/cpu/arm/include/rtems/score/cpu.h
> > index e5b23e7100..dcda4d525c 100644
> > --- a/cpukit/score/cpu/arm/include/rtems/score/cpu.h
> > +++ b/cpukit/score/cpu/arm/include/rtems/score/cpu.h
> > @@ -465,6 +465,11 @@ void _CPU_ISR_install_vector(
> > */
> > void _CPU_Context_switch( Context_Control *run, Context_Control *heir );
> >
> > +RTEMS_NO_RETURN void _CPU_Context_switch_no_return(
> > + Context_Control *executing,
> > + Context_Control *heir
> > +);
> > +
> > RTEMS_NO_RETURN void _CPU_Context_restore( Context_Control *new_context
> );
> >
> > #if defined(ARM_MULTILIB_ARCH_V7M)
> > diff --git a/cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h
> b/cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h
> > index c067501502..c437ded5fb 100644
> > --- a/cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h
> > +++ b/cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h
> > @@ -1054,22 +1054,46 @@ void _CPU_ISR_install_vector(
> > void *_CPU_Thread_Idle_body( uintptr_t ignored );
> >
> > /**
> > + * @brief Peforms a context switch from the executing thread to the heir
> > + * thread.
> > + *
> > * @addtogroup RTEMSScoreCPUExampleContext
> > *
> > * This routine switches from the run context to the heir context.
> > *
> > - * @param[in] run points to the context of the currently executing task
> > - * @param[in] heir points to the context of the heir task
> > + * @param[out] executing points to the context of the currently
> executing task.
> > + *
> > + * @param[in, out] heir points to the context of the heir task.
> > *
> > * Port Specific Information:
> > *
> > * XXX document implementation including references if appropriate
> > */
> > void _CPU_Context_switch(
> > - Context_Control *run,
> > + Context_Control *executing,
> > Context_Control *heir
> > );
> >
> > +/**
> > + * @brief Peforms a context switch from the executing thread to the
> heir thread
> > + * and does not return.
> > + *
> > + * @addtogroup RTEMSScoreCPUExampleContext
> > + *
> > + * This routine shall be a strong alias to _CPU_Context_switch(). It
> shall be
> > + * provided for all target architectures which support an SMP build
> > + * configuration (RTEMS_SMP). The purpose is help to compiler to avoid
> > + * generation of dead code in _Thread_Start_multitasking().
> > + *
> > + * @param[out] executing points to the context of the currently
> executing task.
> > + *
> > + * @param[in, out] heir points to the context of the heir task.
> > + */
> > +RTEMS_NO_RETURN void _CPU_Context_switch_no_return(
> > + Context_Control *executing,
> > + Context_Control *heir
> > +);
> > +
> > /**
> > * @addtogroup RTEMSScoreCPUExampleContext
> > *
> > diff --git a/cpukit/score/cpu/powerpc/include/rtems/score/cpu.h
> b/cpukit/score/cpu/powerpc/include/rtems/score/cpu.h
> > index 996b6f8e60..f22e1cd7ec 100644
> > --- a/cpukit/score/cpu/powerpc/include/rtems/score/cpu.h
> > +++ b/cpukit/score/cpu/powerpc/include/rtems/score/cpu.h
> > @@ -914,6 +914,11 @@ void _CPU_Context_switch(
> > Context_Control *heir
> > );
> >
> > +RTEMS_NO_RETURN void _CPU_Context_switch_no_return(
> > + Context_Control *executing,
> > + Context_Control *heir
> > +);
> > +
> > /*
> > * _CPU_Context_restore
> > *
> > diff --git a/cpukit/score/cpu/riscv/include/rtems/score/cpu.h
> b/cpukit/score/cpu/riscv/include/rtems/score/cpu.h
> > index 38eb92394d..a44b815b12 100644
> > --- a/cpukit/score/cpu/riscv/include/rtems/score/cpu.h
> > +++ b/cpukit/score/cpu/riscv/include/rtems/score/cpu.h
> > @@ -383,6 +383,11 @@ void _CPU_Context_switch(
> > Context_Control *heir
> > );
> >
> > +RTEMS_NO_RETURN void _CPU_Context_switch_no_return(
> > + Context_Control *executing,
> > + Context_Control *heir
> > +);
> > +
> > /*
> > * _CPU_Context_restore
> > *
> > diff --git a/cpukit/score/cpu/riscv/riscv-context-switch.S
> b/cpukit/score/cpu/riscv/riscv-context-switch.S
> > index 96c117b3de..830f8629a4 100644
> > --- a/cpukit/score/cpu/riscv/riscv-context-switch.S
> > +++ b/cpukit/score/cpu/riscv/riscv-context-switch.S
> > @@ -37,9 +37,11 @@
> > .align 2
> >
> > PUBLIC(_CPU_Context_switch)
> > +PUBLIC(_CPU_Context_switch_no_return)
> > PUBLIC(_CPU_Context_restore)
> >
> > SYM(_CPU_Context_switch):
> > +SYM(_CPU_Context_switch_no_return):
> > GET_SELF_CPU_CONTROL a2
> > lw a3, PER_CPU_ISR_DISPATCH_DISABLE(a2)
> >
> > diff --git a/cpukit/score/cpu/sparc/cpu_asm.S
> b/cpukit/score/cpu/sparc/cpu_asm.S
> > index e884fb2f9e..a7b87ad5f8 100644
> > --- a/cpukit/score/cpu/sparc/cpu_asm.S
> > +++ b/cpukit/score/cpu/sparc/cpu_asm.S
> > @@ -57,7 +57,9 @@
> >
> > .align 4
> > PUBLIC(_CPU_Context_switch)
> > + PUBLIC(_CPU_Context_switch_no_return)
> > SYM(_CPU_Context_switch):
> > +SYM(_CPU_Context_switch_no_return):
> > st %g5, [%o0 + G5_OFFSET] ! save the global registers
> >
> > /*
> > diff --git a/cpukit/score/cpu/sparc/include/rtems/score/cpu.h
> b/cpukit/score/cpu/sparc/include/rtems/score/cpu.h
> > index 8c5330b8ce..6c167e3f08 100644
> > --- a/cpukit/score/cpu/sparc/include/rtems/score/cpu.h
> > +++ b/cpukit/score/cpu/sparc/include/rtems/score/cpu.h
> > @@ -971,6 +971,11 @@ void _CPU_Context_switch(
> > Context_Control *heir
> > );
> >
> > +RTEMS_NO_RETURN void _CPU_Context_switch_no_return(
> > + Context_Control *executing,
> > + Context_Control *heir
> > +);
> > +
> > /**
> > * @brief SPARC specific context restore.
> > *
> > diff --git a/cpukit/score/src/threadstartmultitasking.c
> b/cpukit/score/src/threadstartmultitasking.c
> > index a0b465a226..094a535394 100644
> > --- a/cpukit/score/src/threadstartmultitasking.c
> > +++ b/cpukit/score/src/threadstartmultitasking.c
> > @@ -59,7 +59,7 @@ void _Thread_Start_multitasking( void )
> > * executing to the currently selected heir thread.
> > */
> > _CPU_Context_Set_is_executing( &trash, true );
> > - _CPU_Context_switch( &trash, &heir->Registers );
> > + _CPU_Context_switch_no_return( &trash, &heir->Registers );
> > RTEMS_UNREACHABLE();
> > }
> > #else
> > --
> > 2.26.2
> >
> > _______________________________________________
> > devel mailing list
> > devel at rtems.org
> > http://lists.rtems.org/mailman/listinfo/devel
> _______________________________________________
> devel mailing list
> devel at rtems.org
> http://lists.rtems.org/mailman/listinfo/devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.rtems.org/pipermail/devel/attachments/20210517/128d7a70/attachment-0001.html>
More information about the devel
mailing list