Re: [PATCH v4 08/12] arm64: mm: replace TIF_LAZY_MMU with in_lazy_mmu_mode()
From: Ryan Roberts <ryan.roberts@arm.com>
Date: 2025-11-07 15:28:59
Also in:
linux-arm-kernel, linux-mm, lkml, sparclinux, xen-devel
On 29/10/2025 10:09, Kevin Brodsky wrote:
quoted hunk ↗ jump to hunk
The generic lazy_mmu layer now tracks whether a task is in lazy MMU mode. As a result we no longer need a TIF flag for that purpose - let's use the new in_lazy_mmu_mode() helper instead. Signed-off-by: Kevin Brodsky <redacted> --- arch/arm64/include/asm/pgtable.h | 16 +++------------- arch/arm64/include/asm/thread_info.h | 3 +-- 2 files changed, 4 insertions(+), 15 deletions(-)diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 535435248923..61ca88f94551 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h@@ -62,30 +62,21 @@ static inline void emit_pte_barriers(void) static inline void queue_pte_barriers(void) { - unsigned long flags; - if (in_interrupt()) { emit_pte_barriers(); return; } - flags = read_thread_flags(); - - if (flags & BIT(TIF_LAZY_MMU)) { - /* Avoid the atomic op if already set. */ - if (!(flags & BIT(TIF_LAZY_MMU_PENDING))) - set_thread_flag(TIF_LAZY_MMU_PENDING); - } else { + if (in_lazy_mmu_mode()) + test_and_set_thread_flag(TIF_LAZY_MMU_PENDING);
This removes the optimization to only do the atomic set operation if the bit is not already set. I think that should remain.
+ else
emit_pte_barriers();
- }
}
static inline void arch_enter_lazy_mmu_mode(void)
{
if (in_interrupt())
return;Why are you keeping this test? Surely it can go?
quoted hunk ↗ jump to hunk
- - set_thread_flag(TIF_LAZY_MMU); } static inline void arch_flush_lazy_mmu_mode(void)@@ -103,7 +94,6 @@ static inline void arch_leave_lazy_mmu_mode(void) return; arch_flush_lazy_mmu_mode(); - clear_thread_flag(TIF_LAZY_MMU); } #ifdef CONFIG_TRANSPARENT_HUGEPAGEdiff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index f241b8601ebd..4ff8da0767d9 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h@@ -84,8 +84,7 @@ void arch_setup_new_exec(void); #define TIF_SME_VL_INHERIT 28 /* Inherit SME vl_onexec across exec */ #define TIF_KERNEL_FPSTATE 29 /* Task is in a kernel mode FPSIMD section */ #define TIF_TSC_SIGSEGV 30 /* SIGSEGV on counter-timer access */ -#define TIF_LAZY_MMU 31 /* Task in lazy mmu mode */ -#define TIF_LAZY_MMU_PENDING 32 /* Ops pending for lazy mmu mode exit */ +#define TIF_LAZY_MMU_PENDING 31 /* Ops pending for lazy mmu mode exit */ #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)