The following commit has been merged into the timers/nohz branch of tip: Commit-ID: 490f561b783dac2c4825e288e6dbbf83481eea34 Gitweb: https://git.kernel.org/tip/490f561b783dac2c4825e288e6dbbf83481eea34 Author: Frederic Weisbecker <frederic@xxxxxxxxxx> AuthorDate: Mon, 27 Jan 2020 16:41:52 +01:00 Committer: Frederic Weisbecker <frederic@xxxxxxxxxx> CommitterDate: Fri, 14 Feb 2020 16:05:04 +01:00 context-tracking: Introduce CONFIG_HAVE_TIF_NOHZ A few archs (x86, arm, arm64) don't rely anymore on TIF_NOHZ to call into context tracking on user entry/exit but instead use static keys (or not) to optimize those calls. Ideally every arch should migrate to that behaviour in the long run. Settle a config option to let those archs remove their TIF_NOHZ definitions. Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: Paul Burton <paulburton@xxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: David S. Miller <davem@xxxxxxxxxxxxx> --- arch/Kconfig | 16 +++++++++++----- arch/arm/Kconfig | 1 + arch/arm64/Kconfig | 1 + arch/mips/Kconfig | 1 + arch/powerpc/Kconfig | 1 + arch/sparc/Kconfig | 1 + arch/x86/Kconfig | 1 + kernel/context_tracking.c | 2 ++ 8 files changed, 19 insertions(+), 5 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 98de654..dbf420a 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -540,11 +540,17 @@ config HAVE_CONTEXT_TRACKING help Provide kernel/user boundaries probes necessary for subsystems that need it, such as userspace RCU extended quiescent state. - Syscalls need to be wrapped inside user_exit()-user_enter() through - the slow path using TIF_NOHZ flag. Exceptions handlers must be - wrapped as well. Irqs are already protected inside - rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on - irq exit still need to be protected. + Syscalls need to be wrapped inside user_exit()-user_enter(), either + optimized behind static key or through the slow path using TIF_NOHZ + flag. Exceptions handlers must be wrapped as well. Irqs are already + protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal + handling on irq exit still need to be protected. + +config HAVE_TIF_NOHZ + bool + help + Arch relies on TIF_NOHZ and syscall slow path to implement context + tracking calls to user_enter()/user_exit(). config HAVE_VIRT_CPU_ACCOUNTING bool diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 97864aa..38b764c 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -72,6 +72,7 @@ config ARM select HAVE_ARM_SMCCC if CPU_V7 select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32 select HAVE_CONTEXT_TRACKING + select HAVE_TIF_NOHZ select HAVE_COPY_THREAD_TLS select HAVE_C_RECORDMCOUNT select HAVE_DEBUG_KMEMLEAK if !XIP_KERNEL diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 0b30e88..5c945fa 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -140,6 +140,7 @@ config ARM64 select HAVE_CMPXCHG_DOUBLE select HAVE_CMPXCHG_LOCAL select HAVE_CONTEXT_TRACKING + select HAVE_TIF_NOHZ select HAVE_COPY_THREAD_TLS select HAVE_DEBUG_BUGVERBOSE select HAVE_DEBUG_KMEMLEAK diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 797d7f1..2589d47 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -51,6 +51,7 @@ config MIPS select HAVE_ASM_MODVERSIONS select HAVE_CBPF_JIT if !64BIT && !CPU_MICROMIPS select HAVE_CONTEXT_TRACKING + select HAVE_TIF_NOHZ select HAVE_COPY_THREAD_TLS select HAVE_C_RECORDMCOUNT select HAVE_DEBUG_KMEMLEAK diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 497b7d0..6f40af2 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -182,6 +182,7 @@ 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_COPY_THREAD_TLS select HAVE_DEBUG_KMEMLEAK select HAVE_DEBUG_STACKOVERFLOW diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig index c1dd6dd..9cc9ab0 100644 --- a/arch/sparc/Kconfig +++ b/arch/sparc/Kconfig @@ -71,6 +71,7 @@ config SPARC64 select HAVE_FTRACE_MCOUNT_RECORD select HAVE_SYSCALL_TRACEPOINTS select HAVE_CONTEXT_TRACKING + select HAVE_TIF_NOHZ select HAVE_DEBUG_KMEMLEAK select IOMMU_HELPER select SPARSE_IRQ diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index beea770..549eed3 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -211,6 +211,7 @@ config X86 select HAVE_STACK_VALIDATION if X86_64 select HAVE_RSEQ select HAVE_SYSCALL_TRACEPOINTS + select HAVE_TIF_NOHZ if X86_64 select HAVE_UNSTABLE_SCHED_CLOCK select HAVE_USER_RETURN_NOTIFIER select HAVE_GENERIC_VDSO diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 0296b4b..ce43088 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -198,11 +198,13 @@ void __init context_tracking_cpu_set(int cpu) if (initialized) return; +#ifdef CONFIG_HAVE_TIF_NOHZ /* * Set TIF_NOHZ to init/0 and let it propagate to all tasks through fork * This assumes that init is the only task at this early boot stage. */ set_tsk_thread_flag(&init_task, TIF_NOHZ); +#endif WARN_ON_ONCE(!tasklist_empty()); initialized = true;
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