From 750131496b762a1185ae9e9953a569ed1d80d31a Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 31 Oct 2012 12:04:11 +0100 Subject: [PATCH 261/323] arm: Add support for lazy preemption Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.215-rt107.tar.xz Implement the arm pieces for lazy preempt. Signed-off-by: Thomas Gleixner Signed-off-by: Luis Claudio R. Goncalves --- arch/arm/Kconfig | 1 + arch/arm/include/asm/thread_info.h | 5 ++++- arch/arm/kernel/asm-offsets.c | 1 + arch/arm/kernel/entry-armv.S | 19 ++++++++++++++++--- arch/arm/kernel/entry-common.S | 1 + arch/arm/kernel/signal.c | 3 ++- 6 files changed, 25 insertions(+), 5 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index c01251683018d..ee2cbe8ad502d 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -107,6 +107,7 @@ config ARM select HAVE_PERF_EVENTS select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP + 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 fcccf35f5cf96..3b981ad0c3222 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -46,6 +46,7 @@ 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 */ @@ -134,6 +135,7 @@ 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 5 #define TIF_USING_IWMMXT 17 #define TIF_MEMDIE 18 /* is terminating due to OOM killer */ @@ -143,10 +145,10 @@ extern int vfp_restore_user_hwstate(struct user_vfp *, #define TIF_SYSCALL_TRACEPOINT 22 /* syscall tracepoint instrumentation */ #define TIF_SECCOMP 23 /* seccomp syscall filtering active */ - #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) @@ -164,6 +166,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp *, */ #define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \ _TIF_NOTIFY_RESUME | _TIF_UPROBE | \ + _TIF_NEED_RESCHED_LAZY | \ _TIF_NOTIFY_SIGNAL) #endif /* __KERNEL__ */ diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c index 70993af22d80c..024c65c3a0f23 100644 --- a/arch/arm/kernel/asm-offsets.c +++ b/arch/arm/kernel/asm-offsets.c @@ -43,6 +43,7 @@ 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 030351d169aac..d6086559168db 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -206,11 +206,18 @@ __irq_svc: #ifdef CONFIG_PREEMPTION 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 @@ -225,8 +232,14 @@ 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 9b3c737575e91..a30b1a1cc4d18 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -92,6 +92,7 @@ __ret_fast_syscall: ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing movs r1, r1, lsl #16 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 a3a38d0a4c853..f04ccf19ab1fd 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -649,7 +649,8 @@ 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))) -- 2.44.0