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score: PR2183: Fix context switch on SMP

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Fix context switch on SMP for ARM, PowerPC and SPARC.

Atomically test and set the is executing indicator of the heir context
to ensure that at most one processor uses the heir context.  Break the
busy wait loop also due to heir updates.
This commit is contained in:
Sebastian Huber
2014-07-01 10:48:28 +02:00
parent f28f5c4a1d
commit fbda4a8834
8 changed files with 230 additions and 86 deletions
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57
c/src/lib/libbsp/sparc/shared/irq_asm.S
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@@ -7,6 +7,8 @@
* COPYRIGHT (c) 1989-2011.
* On-Line Applications Research Corporation (OAR).
*
* Copyright (c) 2014 embedded brains GmbH
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
@@ -165,17 +167,18 @@ done_flushing:
#if defined(RTEMS_SMP)
! The executing context no longer executes on this processor
stb %g0, [%o0 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET]
st %g0, [%o0 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET]
! Wait for heir context to stop execution
1:
ldub [%o1 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET], %g1
! Try to update the is executing indicator of the heir context
mov 1, %g1
try_update_is_executing:
swap [%o1 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET], %g1
cmp %g1, 0
bne 1b
mov 1, %g1
bne check_is_executing
! The heir context executes now on this processor
stb %g1, [%o1 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET]
! The next load is in a delay slot, which is all right
#endif
ld [%o1 + G5_OFFSET], %g5 ! restore the global registers
@@ -203,6 +206,44 @@ done_flushing:
jmp %o7 + 8 ! return
nop ! delay slot
#if defined(RTEMS_SMP)
check_is_executing:
! Check the is executing indicator of the heir context
ld [%o1 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET], %g1
cmp %g1, 0
beq try_update_is_executing
mov 1, %g1
! Check if a thread dispatch is necessary
ldub [%g6 + PER_CPU_DISPATCH_NEEDED], %g1
cmp %g1, 0
beq check_is_executing
nop
! We have a new heir
! Clear the thread dispatch necessary flag
stub %g0, [%g6 + PER_CPU_DISPATCH_NEEDED]
! Here we assume a strong memory order, otherwise a memory barrier must
! be inserted here
! Read the executing and heir
ld [%g6 + PER_CPU_OFFSET_EXECUTING], %g1
ld [%g6 + PER_CPU_OFFSET_HEIR], %g2
! Calculate the heir context pointer
sub %o1, %g1, %g1
add %g1, %g2, %o1
! Update the executing
st %g2, [%g6 + PER_CPU_OFFSET_EXECUTING]
ba try_update_is_executing
mov 1, %g1
#endif
/*
* void _CPU_Context_restore(
* Context_Control *new_context