105 lines
4.1 KiB
Diff
105 lines
4.1 KiB
Diff
From: Anders Roxell <anders.roxell@linaro.org>
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Date: Thu, 14 May 2015 17:52:17 +0200
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Subject: arch/arm64: Add lazy preempt support
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.1/patches-4.1.3-rt3.tar.xz
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arm64 is missing support for PREEMPT_RT. The main feature which is
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lacking is support for lazy preemption. The arch-specific entry code,
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thread information structure definitions, and associated data tables
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have to be extended to provide this support. Then the Kconfig file has
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to be extended to indicate the support is available, and also to
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indicate that support for full RT preemption is now available.
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Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
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---
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arch/arm64/Kconfig | 1 +
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arch/arm64/include/asm/thread_info.h | 3 +++
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arch/arm64/kernel/asm-offsets.c | 1 +
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arch/arm64/kernel/entry.S | 13 ++++++++++---
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4 files changed, 15 insertions(+), 3 deletions(-)
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--- a/arch/arm64/Kconfig
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+++ b/arch/arm64/Kconfig
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@@ -69,6 +69,7 @@ config ARM64
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select HAVE_PERF_REGS
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select HAVE_PERF_USER_STACK_DUMP
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select HAVE_RCU_TABLE_FREE
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+ select HAVE_PREEMPT_LAZY
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select HAVE_SYSCALL_TRACEPOINTS
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select IRQ_DOMAIN
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select IRQ_FORCED_THREADING
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--- a/arch/arm64/include/asm/thread_info.h
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+++ b/arch/arm64/include/asm/thread_info.h
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@@ -47,6 +47,7 @@ struct thread_info {
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mm_segment_t addr_limit; /* address limit */
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struct task_struct *task; /* main task structure */
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int preempt_count; /* 0 => preemptable, <0 => bug */
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+ int preempt_lazy_count; /* 0 => preemptable, <0 => bug */
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int cpu; /* cpu */
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};
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@@ -101,6 +102,7 @@ static inline struct thread_info *curren
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#define TIF_NEED_RESCHED 1
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#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
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#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
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+#define TIF_NEED_RESCHED_LAZY 4
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#define TIF_NOHZ 7
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#define TIF_SYSCALL_TRACE 8
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#define TIF_SYSCALL_AUDIT 9
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@@ -117,6 +119,7 @@ static inline struct thread_info *curren
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#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
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#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
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#define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE)
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+#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
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#define _TIF_NOHZ (1 << TIF_NOHZ)
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#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
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#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
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--- a/arch/arm64/kernel/asm-offsets.c
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+++ b/arch/arm64/kernel/asm-offsets.c
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@@ -35,6 +35,7 @@ int main(void)
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BLANK();
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DEFINE(TI_FLAGS, offsetof(struct thread_info, flags));
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DEFINE(TI_PREEMPT, offsetof(struct thread_info, preempt_count));
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+ DEFINE(TI_PREEMPT_LAZY, offsetof(struct thread_info, preempt_lazy_count));
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DEFINE(TI_ADDR_LIMIT, offsetof(struct thread_info, addr_limit));
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DEFINE(TI_TASK, offsetof(struct thread_info, task));
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DEFINE(TI_CPU, offsetof(struct thread_info, cpu));
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--- a/arch/arm64/kernel/entry.S
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+++ b/arch/arm64/kernel/entry.S
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@@ -367,11 +367,16 @@ ENDPROC(el1_sync)
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#ifdef CONFIG_PREEMPT
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get_thread_info tsk
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ldr w24, [tsk, #TI_PREEMPT] // get preempt count
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- cbnz w24, 1f // preempt count != 0
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+ cbnz w24, 2f // preempt count != 0
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ldr x0, [tsk, #TI_FLAGS] // get flags
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- tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling?
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- bl el1_preempt
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+ tbnz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling?
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+
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+ ldr w24, [tsk, #TI_PREEMPT_LAZY] // get preempt lazy count
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+ cbnz w24, 2f // preempt lazy count != 0
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+ tbz x0, #TIF_NEED_RESCHED_LAZY, 2f // needs rescheduling?
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1:
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+ bl el1_preempt
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+2:
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#endif
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#ifdef CONFIG_TRACE_IRQFLAGS
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bl trace_hardirqs_on
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@@ -385,6 +390,7 @@ ENDPROC(el1_irq)
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1: bl preempt_schedule_irq // irq en/disable is done inside
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ldr x0, [tsk, #TI_FLAGS] // get new tasks TI_FLAGS
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tbnz x0, #TIF_NEED_RESCHED, 1b // needs rescheduling?
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+ tbnz x0, #TIF_NEED_RESCHED_LAZY, 1b // needs rescheduling?
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ret x24
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#endif
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@@ -622,6 +628,7 @@ ENDPROC(cpu_switch_to)
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str x0, [sp, #S_X0] // returned x0
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work_pending:
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tbnz x1, #TIF_NEED_RESCHED, work_resched
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+ tbnz x1, #TIF_NEED_RESCHED_LAZY, work_resched
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/* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */
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ldr x2, [sp, #S_PSTATE]
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mov x0, sp // 'regs'
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