Revert "arm: Add support for lazy preemption"

This reverts commit 8386f940ea9a9a6a1c690ae7e1d038c3781b1403.

New version of this patch is coming.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

5 files changed, 5 insertions, 25 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4ce79eb994a6..28298d43b4c5 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -116,7 +116,6 @@ config ARM
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
 	select HAVE_POSIX_CPU_TIMERS_TASK_WORK if !KVM
-	select HAVE_PREEMPT_LAZY
 	select MMU_GATHER_RCU_TABLE_FREE if SMP && ARM_LPAE
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RSEQ
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index b02e555e5aa3..7f092cb55a41 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -62,7 +62,6 @@ 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 */
 	__u32			cpu;		/* cpu */
 	__u32			cpu_domain;	/* cpu domain */
 	struct cpu_context_save	cpu_context;	/* cpu context */
@@ -130,7 +129,6 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
 #define TIF_NOTIFY_RESUME	2	/* callback before returning to user */
 #define TIF_UPROBE		3	/* breakpointed or singlestepping */
 #define TIF_NOTIFY_SIGNAL	4	/* signal notifications exist */
-#define TIF_NEED_RESCHED_LAZY	9
 
 #define TIF_USING_IWMMXT	17
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
@@ -150,7 +148,6 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
-#define _TIF_NEED_RESCHED_LAZY	(1 << TIF_NEED_RESCHED_LAZY)
 #define _TIF_USING_IWMMXT	(1 << TIF_USING_IWMMXT)
 
 /* Checks for any syscall work in entry-common.S */
@@ -160,8 +157,7 @@ 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_NEED_RESCHED_LAZY | \
-				 _TIF_SIGPENDING | \
+#define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
 				 _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
 				 _TIF_NOTIFY_SIGNAL)
 
diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index c3bdec7d2df9..2c8d76fd7c66 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -43,7 +43,6 @@ 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_CPU,		offsetof(struct thread_info, cpu));
   DEFINE(TI_CPU_DOMAIN,		offsetof(struct thread_info, cpu_domain));
   DEFINE(TI_CPU_SAVE,		offsetof(struct thread_info, cpu_context));
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index cfb4660e9fea..c39303e5c234 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -222,18 +222,11 @@ __irq_svc:
 
 #ifdef CONFIG_PREEMPTION
 	ldr	r8, [tsk, #TI_PREEMPT]		@ get preempt count
-	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
+	teq	r8, #0				@ if preempt count != 0
 	movne	r0, #0				@ force flags to 0
-	tst	r0, #_TIF_NEED_RESCHED_LAZY
+	tst	r0, #_TIF_NEED_RESCHED
 	blne	svc_preempt
-1:
 #endif
 
 	svc_exit r5, irq = 1			@ return from exception
@@ -248,14 +241,8 @@ 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
-	ldr	r0, [tsk, #TI_PREEMPT_LAZY]	@ get preempt lazy count
-	teq	r0, #0				@ if preempt lazy count != 0
-	beq	1b
-	ret	r8				@ go again
-
+	b	1b
 #endif
 
 __und_fault:
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index b50a3248e79f..e07f359254c3 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -607,8 +607,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 	 */
 	trace_hardirqs_off();
 	do {
-		if (likely(thread_flags & (_TIF_NEED_RESCHED |
-					   _TIF_NEED_RESCHED_LAZY))) {
+		if (likely(thread_flags & _TIF_NEED_RESCHED)) {
 			schedule();
 		} else {
 			if (unlikely(!user_mode(regs)))