Re: [PATCH v5 09/21] powerpc/64: context tracking remove _TIF_NOHZ
From: Christophe Leroy <hidden>
Date: 2021-01-13 14:53:37
Le 13/01/2021 à 08:32, Nicholas Piggin a écrit :
Add context tracking to the system call handler explicitly, and remove _TIF_NOHZ. This saves 35 cycles on gettid system call cost on POWER9 with a CONFIG_NOHZ_FULL kernel.
35 cycles among 100 cycles, or among 5000 cycles ? I meant what pourcentage to you win ? Christophe
quoted hunk ↗ jump to hunk
Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/Kconfig | 1 - arch/powerpc/include/asm/thread_info.h | 4 +--- arch/powerpc/kernel/ptrace/ptrace.c | 4 ---- arch/powerpc/kernel/signal.c | 4 ---- arch/powerpc/kernel/syscall_64.c | 10 ++++++++++ 5 files changed, 11 insertions(+), 12 deletions(-)diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 107bb4319e0e..28d5a1b1510f 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig@@ -196,7 +196,6 @@ config PPC select HAVE_STACKPROTECTOR if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13) select HAVE_STACKPROTECTOR if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2) select HAVE_CONTEXT_TRACKING if PPC64 - select HAVE_TIF_NOHZ if PPC64 select HAVE_DEBUG_KMEMLEAK select HAVE_DEBUG_STACKOVERFLOW select HAVE_DYNAMIC_FTRACEdiff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h index 3d8a47af7a25..386d576673a1 100644 --- a/arch/powerpc/include/asm/thread_info.h +++ b/arch/powerpc/include/asm/thread_info.h@@ -94,7 +94,6 @@ void arch_setup_new_exec(void); #define TIF_PATCH_PENDING 6 /* pending live patching update */ #define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */ #define TIF_SINGLESTEP 8 /* singlestepping active */ -#define TIF_NOHZ 9 /* in adaptive nohz mode */ #define TIF_SECCOMP 10 /* secure computing */ #define TIF_RESTOREALL 11 /* Restore all regs (implies NOERROR) */ #define TIF_NOERROR 12 /* Force successful syscall return */@@ -128,11 +127,10 @@ void arch_setup_new_exec(void); #define _TIF_UPROBE (1<<TIF_UPROBE) #define _TIF_SYSCALL_TRACEPOINT (1<<TIF_SYSCALL_TRACEPOINT) #define _TIF_EMULATE_STACK_STORE (1<<TIF_EMULATE_STACK_STORE) -#define _TIF_NOHZ (1<<TIF_NOHZ) #define _TIF_SYSCALL_EMU (1<<TIF_SYSCALL_EMU) #define _TIF_SYSCALL_DOTRACE (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT | \ - _TIF_NOHZ | _TIF_SYSCALL_EMU) + _TIF_SYSCALL_EMU) #define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \ _TIF_NOTIFY_RESUME | _TIF_UPROBE | \diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c index 3d44b73adb83..4f3d4ff3728c 100644 --- a/arch/powerpc/kernel/ptrace/ptrace.c +++ b/arch/powerpc/kernel/ptrace/ptrace.c@@ -262,8 +262,6 @@ long do_syscall_trace_enter(struct pt_regs *regs) { u32 flags; - user_exit(); - flags = READ_ONCE(current_thread_info()->flags) & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE);@@ -340,8 +338,6 @@ void do_syscall_trace_leave(struct pt_regs *regs) step = test_thread_flag(TIF_SINGLESTEP); if (step || test_thread_flag(TIF_SYSCALL_TRACE)) tracehook_report_syscall_exit(regs, step); - - user_enter(); } void __init pt_regs_check(void);diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c index 53782aa60ade..9ded046edb0e 100644 --- a/arch/powerpc/kernel/signal.c +++ b/arch/powerpc/kernel/signal.c@@ -282,8 +282,6 @@ static void do_signal(struct task_struct *tsk) void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags) { - user_exit(); - if (thread_info_flags & _TIF_UPROBE) uprobe_notify_resume(regs);@@ -299,8 +297,6 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags) tracehook_notify_resume(regs); rseq_handle_notify_resume(NULL, regs); } - - user_enter(); } static unsigned long get_tm_stackpointer(struct task_struct *tsk)diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c index dd87b2118620..d7d256a7a41f 100644 --- a/arch/powerpc/kernel/syscall_64.c +++ b/arch/powerpc/kernel/syscall_64.c@@ -1,9 +1,11 @@ // SPDX-License-Identifier: GPL-2.0-or-later +#include <linux/context_tracking.h> #include <linux/err.h> #include <asm/asm-prototypes.h> #include <asm/kup.h> #include <asm/cputime.h> +#include <asm/interrupt.h> #include <asm/hw_irq.h> #include <asm/interrupt.h> #include <asm/kprobes.h>@@ -28,6 +30,9 @@ notrace long system_call_exception(long r3, long r4, long r5, if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG)) BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED); + CT_WARN_ON(ct_state() == CONTEXT_KERNEL); + user_exit_irqoff(); + trace_hardirqs_off(); /* finish reconciling */ if (IS_ENABLED(CONFIG_PPC_BOOK3S))@@ -182,6 +187,8 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3, unsigned long ti_flags; unsigned long ret = 0; + CT_WARN_ON(ct_state() == CONTEXT_USER); + kuap_check_amr(); regs->result = r3;@@ -258,8 +265,11 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3, } } + user_enter_irqoff(); + /* scv need not set RI=0 because SRRs are not used */ if (unlikely(!prep_irq_for_enabled_exit(!scv))) { + user_exit_irqoff(); local_irq_enable(); goto again; }