135 lines
5.2 KiB
Diff
135 lines
5.2 KiB
Diff
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From 730dd6e7a0d54f25ffde85be6dd31fdcac74ac01 Mon Sep 17 00:00:00 2001
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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: [PATCH 304/304] arch/arm64: Add lazy preempt support
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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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Change-Id: I14be0f2747e4b745a7210fa9e74d0a5ee3a00a02
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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 | 8 +++++++-
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arch/arm64/kernel/asm-offsets.c | 1 +
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arch/arm64/kernel/entry.S | 12 +++++++++---
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arch/arm64/kernel/signal.c | 2 +-
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5 files changed, 19 insertions(+), 5 deletions(-)
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diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
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index e40339726039..1e97dd7efb5a 100644
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--- a/arch/arm64/Kconfig
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+++ b/arch/arm64/Kconfig
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@@ -92,6 +92,7 @@ config ARM64
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select HAVE_PERF_EVENTS
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select HAVE_PERF_REGS
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select HAVE_PERF_USER_STACK_DUMP
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+ select HAVE_PREEMPT_LAZY
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select HAVE_REGS_AND_STACK_ACCESS_API
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select HAVE_RCU_TABLE_FREE
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select HAVE_SYSCALL_TRACEPOINTS
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diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
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index 5b96df618873..f7c4271d565c 100644
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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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@@ -51,6 +51,8 @@ struct thread_info {
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u64 ttbr0; /* saved TTBR0_EL1 */
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#endif
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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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#define INIT_THREAD_INFO(tsk) \
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@@ -85,6 +87,7 @@ struct thread_info {
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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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@@ -102,6 +105,7 @@ struct thread_info {
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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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@@ -111,7 +115,9 @@ struct thread_info {
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#define _TIF_DEPRECATED_WARN (1 << TIF_DEPRECATED_WARN)
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#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
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- _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE)
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+ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
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+ _TIF_NEED_RESCHED_LAZY)
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+#define _TIF_NEED_RESCHED_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
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#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
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_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
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diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
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index b2debecb51e2..ae495cc3cdb2 100644
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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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@@ -39,6 +39,7 @@ int main(void)
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BLANK();
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DEFINE(TSK_TI_FLAGS, offsetof(struct task_struct, thread_info.flags));
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DEFINE(TSK_TI_PREEMPT, offsetof(struct task_struct, thread_info.preempt_count));
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+ DEFINE(TSK_TI_PREEMPT_LAZY, offsetof(struct task_struct, thread_info.preempt_lazy_count));
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DEFINE(TSK_TI_ADDR_LIMIT, offsetof(struct task_struct, thread_info.addr_limit));
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#ifdef CONFIG_ARM64_SW_TTBR0_PAN
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DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0));
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diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
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index 09bf87b0a3a7..91241924ab1d 100644
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--- a/arch/arm64/kernel/entry.S
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+++ b/arch/arm64/kernel/entry.S
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@@ -564,11 +564,16 @@ el1_irq:
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#ifdef CONFIG_PREEMPT
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ldr w24, [tsk, #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, #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, #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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@@ -582,6 +587,7 @@ el1_preempt:
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1: bl preempt_schedule_irq // irq en/disable is done inside
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ldr x0, [tsk, #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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diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
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index 404dd67080b9..639dc6d12e72 100644
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--- a/arch/arm64/kernel/signal.c
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+++ b/arch/arm64/kernel/signal.c
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@@ -409,7 +409,7 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
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*/
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trace_hardirqs_off();
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do {
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- if (thread_flags & _TIF_NEED_RESCHED) {
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+ if (thread_flags & _TIF_NEED_RESCHED_MASK) {
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schedule();
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} else {
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local_irq_enable();
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--
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2.28.0
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