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| author | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2015-09-25 14:34:24 +0200 |
|---|---|---|
| committer | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2015-09-28 13:56:57 +0200 |
| commit | 258ad71e9626c16f30b40e06c321326636c976ff (patch) | |
| tree | da6e210947d590159796434bf04cf364247ac20a /c/src/lib/libbsp/sparc/shared/irq_asm.S | |
| parent | SMP: Simplify thread lock operations (diff) | |
| download | rtems-258ad71e9626c16f30b40e06c321326636c976ff.tar.bz2 | |
SMP: Fix and optimize thread dispatching
According to the C11 and C++11 memory models only a read-modify-write
operation guarantees that we read the last value written in modification
order. Avoid the sequential consistent thread fence and instead use the
inter-processor interrupt to set the thread dispatch necessary
indicator.
Diffstat (limited to '')
| -rw-r--r-- | c/src/lib/libbsp/sparc/shared/irq_asm.S | 20 |
1 files changed, 7 insertions, 13 deletions
diff --git a/c/src/lib/libbsp/sparc/shared/irq_asm.S b/c/src/lib/libbsp/sparc/shared/irq_asm.S index f7222e7623..9d8600e0fe 100644 --- a/c/src/lib/libbsp/sparc/shared/irq_asm.S +++ b/c/src/lib/libbsp/sparc/shared/irq_asm.S @@ -236,24 +236,18 @@ check_is_executing: 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 + ! We may have a new heir ! Read the executing and heir ld [%g6 + PER_CPU_OFFSET_EXECUTING], %g1 ld [%g6 + PER_CPU_OFFSET_HEIR], %g2 + ! Update the executing only if necessary to avoid cache line + ! monopolization. + cmp %g1, %g2 + beq try_update_is_executing + mov 1, %g1 + ! Calculate the heir context pointer sub %o1, %g1, %g1 add %g1, %g2, %o1 |