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entry: Inline syscall_exit_to_user_mode()

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Similar to commit 221a164035 ("entry: Move syscall_enter_from_user_mode()
to header file"), move syscall_exit_to_user_mode() to the header file as
well.

Testing was done with the byte-unixbench syscall benchmark (which calls
getpid) and QEMU. On riscv I measured a 7.09246% improvement, on x86 a
2.98843% improvement, on loongarch a 6.07954% improvement, and on s390 a
11.1328% improvement.

The Intel bot also reported "kernel test robot noticed a 1.9% improvement
of stress-ng.seek.ops_per_sec".

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/all/20250320-riscv_optimize_entry-v6-4-63e187e26041@rivosinc.com
Link: https://lore.kernel.org/linux-riscv/202502051555.85ae6844-lkp@intel.com/
This commit is contained in:
Charlie Jenkins 2025-03-20 10:29:24 -07:00 committed by Thomas Gleixner
parent 7ace1602ab
commit e43b8bb56e
2 changed files with 42 additions and 50 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

43
include/linux/entry-common.h
View file

@ -14,6 +14,7 @@
#include <linux/kmsan.h>
#include <asm/entry-common.h>
#include <asm/syscall.h>
/*
* Define dummy _TIF work flags if not defined by the architecture or for
@ -366,6 +367,15 @@ static __always_inline void exit_to_user_mode(void)
lockdep_hardirqs_on(CALLER_ADDR0);
}
/**
* syscall_exit_work - Handle work before returning to user mode
* @regs: Pointer to current pt_regs
* @work: Current thread syscall work
*
* Do one-time syscall specific work.
*/
void syscall_exit_work(struct pt_regs *regs, unsigned long work);
/**
* syscall_exit_to_user_mode_work - Handle work before returning to user mode
* @regs: Pointer to currents pt_regs
@ -379,7 +389,30 @@ static __always_inline void exit_to_user_mode(void)
* make the final state transitions. Interrupts must stay disabled between
* return from this function and the invocation of exit_to_user_mode().
*/
void syscall_exit_to_user_mode_work(struct pt_regs *regs);
static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
{
unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
unsigned long nr = syscall_get_nr(current, regs);
CT_WARN_ON(ct_state() != CT_STATE_KERNEL);
if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
local_irq_enable();
}
rseq_syscall(regs);
/*
* Do one-time syscall specific work. If these work items are
* enabled, we want to run them exactly once per syscall exit with
* interrupts enabled.
*/
if (unlikely(work & SYSCALL_WORK_EXIT))
syscall_exit_work(regs, work);
local_irq_disable_exit_to_user();
exit_to_user_mode_prepare(regs);
}
/**
* syscall_exit_to_user_mode - Handle work before returning to user mode
@ -410,7 +443,13 @@ void syscall_exit_to_user_mode_work(struct pt_regs *regs);
* exit_to_user_mode(). This function is preferred unless there is a
* compelling architectural reason to use the separate functions.
*/
void syscall_exit_to_user_mode(struct pt_regs *regs);
static __always_inline void syscall_exit_to_user_mode(struct pt_regs *regs)
{
instrumentation_begin();
syscall_exit_to_user_mode_work(regs);
instrumentation_end();
exit_to_user_mode();
}
/**
* irqentry_enter_from_user_mode - Establish state before invoking the irq handler

49
kernel/entry/common.c
View file

@ -146,7 +146,7 @@ static inline bool report_single_step(unsigned long work)
return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
}
static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
void syscall_exit_work(struct pt_regs *regs, unsigned long work)
{
bool step;
@ -173,53 +173,6 @@ static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
ptrace_report_syscall_exit(regs, step);
}
/*
* Syscall specific exit to user mode preparation. Runs with interrupts
* enabled.
*/
static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
{
unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
unsigned long nr = syscall_get_nr(current, regs);
CT_WARN_ON(ct_state() != CT_STATE_KERNEL);
if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
local_irq_enable();
}
rseq_syscall(regs);
/*
* Do one-time syscall specific work. If these work items are
* enabled, we want to run them exactly once per syscall exit with
* interrupts enabled.
*/
if (unlikely(work & SYSCALL_WORK_EXIT))
syscall_exit_work(regs, work);
}
static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
{
syscall_exit_to_user_mode_prepare(regs);
local_irq_disable_exit_to_user();
exit_to_user_mode_prepare(regs);
}
void syscall_exit_to_user_mode_work(struct pt_regs *regs)
{
__syscall_exit_to_user_mode_work(regs);
}
__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
{
instrumentation_begin();
__syscall_exit_to_user_mode_work(regs);
instrumentation_end();
exit_to_user_mode();
}
noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
{
enter_from_user_mode(regs);