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linuxkit/kernel/patches-4.14.x-rt/0384-arm-Add-support-for-lazy-preemption.patch
Tiejun Chen ef9302bc01 update -rt to 4.14.87-rt50 
Signed-off-by: Tiejun Chen <tiejunc@vmware.com>
2019-01-14 20:49:28 -08:00

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From d43c1351f9ca08417f637274c72a3026ca6c8485 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 31 Oct 2012 12:04:11 +0100
Subject: [PATCH 384/450] arm: Add support for lazy preemption
Implement the arm pieces for lazy preempt.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/arm/Kconfig | 1 +
arch/arm/include/asm/thread_info.h | 8 ++++++--
arch/arm/kernel/asm-offsets.c | 1 +
arch/arm/kernel/entry-armv.S | 19 ++++++++++++++++---
arch/arm/kernel/entry-common.S | 9 +++++++--
arch/arm/kernel/signal.c | 3 ++-
6 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ac05a027539a..558b0995e94a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -85,6 +85,7 @@ config ARM
select HAVE_PERF_EVENTS
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
+ select HAVE_PREEMPT_LAZY
select HAVE_RCU_TABLE_FREE if (SMP && ARM_LPAE)
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_SYSCALL_TRACEPOINTS
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 57d2ad9c75ca..cdfb6855943b 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -49,6 +49,7 @@ struct cpu_context_save {
struct thread_info {
unsigned long flags; /* low level flags */
int preempt_count; /* 0 => preemptable, <0 => bug */
+ int preempt_lazy_count; /* 0 => preemptable, <0 => bug */
mm_segment_t addr_limit; /* address limit */
struct task_struct *task; /* main task structure */
__u32 cpu; /* cpu */
@@ -142,7 +143,8 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
#define TIF_SYSCALL_TRACE 4 /* syscall trace active */
#define TIF_SYSCALL_AUDIT 5 /* syscall auditing active */
#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
-#define TIF_SECCOMP 7 /* seccomp syscall filtering active */
+#define TIF_SECCOMP 8 /* seccomp syscall filtering active */
+#define TIF_NEED_RESCHED_LAZY 7
#define TIF_NOHZ 12 /* in adaptive nohz mode */
#define TIF_USING_IWMMXT 17
@@ -152,6 +154,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
+#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
#define _TIF_UPROBE (1 << TIF_UPROBE)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
@@ -167,7 +170,8 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
* Change these and you break ASM code in entry-common.S
*/
#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
- _TIF_NOTIFY_RESUME | _TIF_UPROBE)
+ _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
+ _TIF_NEED_RESCHED_LAZY)
#endif /* __KERNEL__ */
#endif /* __ASM_ARM_THREAD_INFO_H */
diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index 608008229c7d..3866da3f7bb7 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -65,6 +65,7 @@ int main(void)
BLANK();
DEFINE(TI_FLAGS, offsetof(struct thread_info, flags));
DEFINE(TI_PREEMPT, offsetof(struct thread_info, preempt_count));
+ DEFINE(TI_PREEMPT_LAZY, offsetof(struct thread_info, preempt_lazy_count));
DEFINE(TI_ADDR_LIMIT, offsetof(struct thread_info, addr_limit));
DEFINE(TI_TASK, offsetof(struct thread_info, task));
DEFINE(TI_CPU, offsetof(struct thread_info, cpu));
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index fbc707626b3e..b434c59d2b64 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -220,11 +220,18 @@ __irq_svc:
#ifdef CONFIG_PREEMPT
ldr r8, [tsk, #TI_PREEMPT] @ get preempt count
- ldr r0, [tsk, #TI_FLAGS] @ get flags
teq r8, #0 @ if preempt count != 0
+ bne 1f @ return from exeption
+ ldr r0, [tsk, #TI_FLAGS] @ get flags
+ tst r0, #_TIF_NEED_RESCHED @ if NEED_RESCHED is set
+ blne svc_preempt @ preempt!
+
+ ldr r8, [tsk, #TI_PREEMPT_LAZY] @ get preempt lazy count
+ teq r8, #0 @ if preempt lazy count != 0
movne r0, #0 @ force flags to 0
- tst r0, #_TIF_NEED_RESCHED
+ tst r0, #_TIF_NEED_RESCHED_LAZY
blne svc_preempt
+1:
#endif
svc_exit r5, irq = 1 @ return from exception
@@ -239,8 +246,14 @@ svc_preempt:
1: bl preempt_schedule_irq @ irq en/disable is done inside
ldr r0, [tsk, #TI_FLAGS] @ get new tasks TI_FLAGS
tst r0, #_TIF_NEED_RESCHED
+ bne 1b
+ tst r0, #_TIF_NEED_RESCHED_LAZY
reteq r8 @ go again
- b 1b
+ ldr r0, [tsk, #TI_PREEMPT_LAZY] @ get preempt lazy count
+ teq r0, #0 @ if preempt lazy count != 0
+ beq 1b
+ ret r8 @ go again
+
#endif
__und_fault:
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 54c10503d71f..3fdeade24e3f 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -53,7 +53,9 @@ ret_fast_syscall:
cmp r2, #TASK_SIZE
blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing
- tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
+ tst r1, #((_TIF_SYSCALL_WORK | _TIF_WORK_MASK) & ~_TIF_SECCOMP)
+ bne fast_work_pending
+ tst r1, #_TIF_SECCOMP
bne fast_work_pending
@@ -83,8 +85,11 @@ ret_fast_syscall:
cmp r2, #TASK_SIZE
blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing
- tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
+ tst r1, #((_TIF_SYSCALL_WORK | _TIF_WORK_MASK) & ~_TIF_SECCOMP)
+ bne do_slower_path
+ tst r1, #_TIF_SECCOMP
beq no_work_pending
+do_slower_path:
UNWIND(.fnend )
ENDPROC(ret_fast_syscall)
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index cdfe52b15a0a..198cf8bf0b37 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -615,7 +615,8 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
*/
trace_hardirqs_off();
do {
- if (likely(thread_flags & _TIF_NEED_RESCHED)) {
+ if (likely(thread_flags & (_TIF_NEED_RESCHED |
+ _TIF_NEED_RESCHED_LAZY))) {
schedule();
} else {
if (unlikely(!user_mode(regs)))
--
2.19.2
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