107 lines
3.9 KiB
Diff
107 lines
3.9 KiB
Diff
Subject: arm: Add support for lazy preemption
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Wed, 31 Oct 2012 12:04:11 +0100
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4.1-rt6.tar.xz
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Implement the arm pieces for lazy preempt.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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arch/arm/Kconfig | 1 +
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arch/arm/include/asm/thread_info.h | 3 +++
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arch/arm/kernel/asm-offsets.c | 1 +
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arch/arm/kernel/entry-armv.S | 13 +++++++++++--
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arch/arm/kernel/signal.c | 3 ++-
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5 files changed, 18 insertions(+), 3 deletions(-)
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--- a/arch/arm/Kconfig
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+++ b/arch/arm/Kconfig
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@@ -68,6 +68,7 @@ config ARM
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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_RCU_TABLE_FREE if (SMP && ARM_LPAE)
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select HAVE_REGS_AND_STACK_ACCESS_API
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select HAVE_SYSCALL_TRACEPOINTS
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--- a/arch/arm/include/asm/thread_info.h
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+++ b/arch/arm/include/asm/thread_info.h
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@@ -49,6 +49,7 @@ struct cpu_context_save {
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struct thread_info {
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unsigned long flags; /* low level flags */
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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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mm_segment_t addr_limit; /* address limit */
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struct task_struct *task; /* main task structure */
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__u32 cpu; /* cpu */
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@@ -143,6 +144,7 @@ extern int vfp_restore_user_hwstate(stru
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#define TIF_SYSCALL_AUDIT 5 /* syscall auditing active */
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#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
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#define TIF_SECCOMP 7 /* seccomp syscall filtering active */
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+#define TIF_NEED_RESCHED_LAZY 8
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#define TIF_NOHZ 12 /* in adaptive nohz mode */
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#define TIF_USING_IWMMXT 17
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@@ -152,6 +154,7 @@ extern int vfp_restore_user_hwstate(stru
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#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
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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_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
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#define _TIF_UPROBE (1 << TIF_UPROBE)
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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/arm/kernel/asm-offsets.c
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+++ b/arch/arm/kernel/asm-offsets.c
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@@ -65,6 +65,7 @@ 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/arm/kernel/entry-armv.S
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+++ b/arch/arm/kernel/entry-armv.S
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@@ -215,11 +215,18 @@ ENDPROC(__dabt_svc)
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#ifdef CONFIG_PREEMPT
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get_thread_info tsk
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ldr r8, [tsk, #TI_PREEMPT] @ get preempt count
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- ldr r0, [tsk, #TI_FLAGS] @ get flags
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teq r8, #0 @ if preempt count != 0
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+ bne 1f @ return from exeption
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+ ldr r0, [tsk, #TI_FLAGS] @ get flags
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+ tst r0, #_TIF_NEED_RESCHED @ if NEED_RESCHED is set
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+ blne svc_preempt @ preempt!
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+
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+ ldr r8, [tsk, #TI_PREEMPT_LAZY] @ get preempt lazy count
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+ teq r8, #0 @ if preempt lazy count != 0
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movne r0, #0 @ force flags to 0
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- tst r0, #_TIF_NEED_RESCHED
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+ tst r0, #_TIF_NEED_RESCHED_LAZY
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blne svc_preempt
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+1:
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#endif
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svc_exit r5, irq = 1 @ return from exception
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@@ -234,6 +241,8 @@ ENDPROC(__irq_svc)
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1: bl preempt_schedule_irq @ irq en/disable is done inside
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ldr r0, [tsk, #TI_FLAGS] @ get new tasks TI_FLAGS
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tst r0, #_TIF_NEED_RESCHED
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+ bne 1b
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+ tst r0, #_TIF_NEED_RESCHED_LAZY
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reteq r8 @ go again
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b 1b
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#endif
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--- a/arch/arm/kernel/signal.c
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+++ b/arch/arm/kernel/signal.c
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@@ -572,7 +572,8 @@ do_work_pending(struct pt_regs *regs, un
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*/
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trace_hardirqs_off();
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do {
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- if (likely(thread_flags & _TIF_NEED_RESCHED)) {
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+ if (likely(thread_flags & (_TIF_NEED_RESCHED |
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+ _TIF_NEED_RESCHED_LAZY))) {
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schedule();
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} else {
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if (unlikely(!user_mode(regs)))
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