NOHZ full updates:
- Remove TIF_NOHZ from 3 architectures
These architectures use a static key to decide whether context tracking
needs to be invoked and the TIF_NOHZ flag just causes a pointless
slowpath execution for nothing.
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Merge tag 'timers-nohz-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull NOHZ update from Thomas Gleixner:
"Remove TIF_NOHZ from three architectures
These architectures use a static key to decide whether context
tracking needs to be invoked and the TIF_NOHZ flag just causes a
pointless slowpath execution for nothing"
* tag 'timers-nohz-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
arm64: Remove TIF_NOHZ
arm: Remove TIF_NOHZ
x86: Remove TIF_NOHZ
context-tracking: Introduce CONFIG_HAVE_TIF_NOHZ
x86/entry: Remove _TIF_NOHZ from _TIF_WORK_SYSCALL_ENTRY
This commit is contained in:
Linus Torvalds
commit
336622e9fc
16
arch/Kconfig
16
arch/Kconfig
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@ -540,11 +540,17 @@ config HAVE_CONTEXT_TRACKING
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help
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Provide kernel/user boundaries probes necessary for subsystems
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that need it, such as userspace RCU extended quiescent state.
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Syscalls need to be wrapped inside user_exit()-user_enter() through
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the slow path using TIF_NOHZ flag. Exceptions handlers must be
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wrapped as well. Irqs are already protected inside
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rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
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irq exit still need to be protected.
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Syscalls need to be wrapped inside user_exit()-user_enter(), either
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optimized behind static key or through the slow path using TIF_NOHZ
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flag. Exceptions handlers must be wrapped as well. Irqs are already
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protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
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handling on irq exit still need to be protected.
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config HAVE_TIF_NOHZ
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bool
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help
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Arch relies on TIF_NOHZ and syscall slow path to implement context
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tracking calls to user_enter()/user_exit().
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config HAVE_VIRT_CPU_ACCOUNTING
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bool
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@ -141,7 +141,6 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
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#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
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#define TIF_SECCOMP 7 /* seccomp syscall filtering active */
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#define TIF_NOHZ 12 /* in adaptive nohz mode */
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#define TIF_USING_IWMMXT 17
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#define TIF_MEMDIE 18 /* is terminating due to OOM killer */
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#define TIF_RESTORE_SIGMASK 20
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@ -63,7 +63,6 @@ void arch_release_task_struct(struct task_struct *tsk);
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#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
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#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
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#define TIF_FSCHECK 5 /* Check FS is USER_DS on return */
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#define TIF_NOHZ 7
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#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
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#define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
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#define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
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@ -83,7 +82,6 @@ void arch_release_task_struct(struct task_struct *tsk);
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#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
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#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
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#define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE)
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#define _TIF_NOHZ (1 << TIF_NOHZ)
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#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
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#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
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#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
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@ -100,7 +98,7 @@ void arch_release_task_struct(struct task_struct *tsk);
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#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
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_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
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_TIF_NOHZ | _TIF_SYSCALL_EMU)
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_TIF_SYSCALL_EMU)
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#define INIT_THREAD_INFO(tsk) \
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{ \
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@ -51,6 +51,7 @@ config MIPS
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select HAVE_ASM_MODVERSIONS
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select HAVE_CBPF_JIT if !64BIT && !CPU_MICROMIPS
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select HAVE_CONTEXT_TRACKING
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select HAVE_TIF_NOHZ
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select HAVE_COPY_THREAD_TLS
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select HAVE_C_RECORDMCOUNT
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select HAVE_DEBUG_KMEMLEAK
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@ -182,6 +182,7 @@ config PPC
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select HAVE_STACKPROTECTOR if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
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select HAVE_STACKPROTECTOR if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2)
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select HAVE_CONTEXT_TRACKING if PPC64
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select HAVE_TIF_NOHZ if PPC64
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select HAVE_COPY_THREAD_TLS
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select HAVE_DEBUG_KMEMLEAK
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select HAVE_DEBUG_STACKOVERFLOW
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@ -71,6 +71,7 @@ config SPARC64
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select HAVE_FTRACE_MCOUNT_RECORD
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select HAVE_SYSCALL_TRACEPOINTS
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select HAVE_CONTEXT_TRACKING
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select HAVE_TIF_NOHZ
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select HAVE_DEBUG_KMEMLEAK
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select IOMMU_HELPER
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select SPARSE_IRQ
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@ -92,7 +92,6 @@ struct thread_info {
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#define TIF_NOCPUID 15 /* CPUID is not accessible in userland */
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#define TIF_NOTSC 16 /* TSC is not accessible in userland */
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#define TIF_IA32 17 /* IA32 compatibility process */
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#define TIF_NOHZ 19 /* in adaptive nohz mode */
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#define TIF_MEMDIE 20 /* is terminating due to OOM killer */
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#define TIF_POLLING_NRFLAG 21 /* idle is polling for TIF_NEED_RESCHED */
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#define TIF_IO_BITMAP 22 /* uses I/O bitmap */
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@ -122,7 +121,6 @@ struct thread_info {
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#define _TIF_NOCPUID (1 << TIF_NOCPUID)
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#define _TIF_NOTSC (1 << TIF_NOTSC)
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#define _TIF_IA32 (1 << TIF_IA32)
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#define _TIF_NOHZ (1 << TIF_NOHZ)
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#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
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#define _TIF_IO_BITMAP (1 << TIF_IO_BITMAP)
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#define _TIF_FORCED_TF (1 << TIF_FORCED_TF)
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@ -133,14 +131,10 @@ struct thread_info {
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#define _TIF_X32 (1 << TIF_X32)
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#define _TIF_FSCHECK (1 << TIF_FSCHECK)
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/*
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* work to do in syscall_trace_enter(). Also includes TIF_NOHZ for
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* enter_from_user_mode()
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*/
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/* Work to do before invoking the actual syscall. */
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#define _TIF_WORK_SYSCALL_ENTRY \
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(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | _TIF_SYSCALL_AUDIT | \
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_TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT | \
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_TIF_NOHZ)
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_TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT)
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/* flags to check in __switch_to() */
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#define _TIF_WORK_CTXSW_BASE \
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@ -198,11 +198,13 @@ void __init context_tracking_cpu_set(int cpu)
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if (initialized)
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return;
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#ifdef CONFIG_HAVE_TIF_NOHZ
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/*
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* Set TIF_NOHZ to init/0 and let it propagate to all tasks through fork
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* This assumes that init is the only task at this early boot stage.
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*/
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set_tsk_thread_flag(&init_task, TIF_NOHZ);
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#endif
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WARN_ON_ONCE(!tasklist_empty());
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initialized = true;
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