Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
+19
-17
+11
-5
arch/Kconfig
+11
-5
arch/Kconfig
···
540
540
help
541
541
Provide kernel/user boundaries probes necessary for subsystems
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542
that need it, such as userspace RCU extended quiescent state.
543
-
Syscalls need to be wrapped inside user_exit()-user_enter() through
544
-
the slow path using TIF_NOHZ flag. Exceptions handlers must be
545
-
wrapped as well. Irqs are already protected inside
546
-
rcu_irq_enter/rcu_irq_exit() but preemption or signal handling on
547
-
irq exit still need to be protected.
543
+
Syscalls need to be wrapped inside user_exit()-user_enter(), either
544
+
optimized behind static key or through the slow path using TIF_NOHZ
545
+
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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+
549
+
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
553
+
tracking calls to user_enter()/user_exit().
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554
549
555
config HAVE_VIRT_CPU_ACCOUNTING
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bool
-1
arch/arm/include/asm/thread_info.h
-1
arch/arm/include/asm/thread_info.h
···
141
141
#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
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#define TIF_SECCOMP 7 /* seccomp syscall filtering active */
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144
-
#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
+1
-3
arch/arm64/include/asm/thread_info.h
+1
-3
arch/arm64/include/asm/thread_info.h
···
63
63
#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
64
64
#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
65
65
#define TIF_FSCHECK 5 /* Check FS is USER_DS on return */
66
-
#define TIF_NOHZ 7
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66
#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
68
67
#define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
69
68
#define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
···
82
83
#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)
85
-
#define _TIF_NOHZ (1 << TIF_NOHZ)
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86
#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)
···
98
100
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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)
102
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#define INIT_THREAD_INFO(tsk) \
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106
{ \
+1
arch/mips/Kconfig
+1
arch/mips/Kconfig
+1
arch/powerpc/Kconfig
+1
arch/powerpc/Kconfig
···
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182
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
185
+
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
+1
arch/sparc/Kconfig
+1
arch/sparc/Kconfig
+2
-8
arch/x86/include/asm/thread_info.h
+2
-8
arch/x86/include/asm/thread_info.h
···
92
92
#define TIF_NOCPUID 15 /* CPUID is not accessible in userland */
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#define TIF_NOTSC 16 /* TSC is not accessible in userland */
94
94
#define TIF_IA32 17 /* IA32 compatibility process */
95
-
#define TIF_NOHZ 19 /* in adaptive nohz mode */
96
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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 */
···
121
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#define _TIF_NOCPUID (1 << TIF_NOCPUID)
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#define _TIF_NOTSC (1 << TIF_NOTSC)
123
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#define _TIF_IA32 (1 << TIF_IA32)
124
-
#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)
···
131
133
#define _TIF_X32 (1 << TIF_X32)
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#define _TIF_FSCHECK (1 << TIF_FSCHECK)
133
135
134
-
/*
135
-
* work to do in syscall_trace_enter(). Also includes TIF_NOHZ for
136
-
* enter_from_user_mode()
137
-
*/
136
+
/* 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 | \
141
-
_TIF_NOHZ)
139
+
_TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT)
142
140
143
141
/* flags to check in __switch_to() */
144
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#define _TIF_WORK_CTXSW_BASE \
+2
kernel/context_tracking.c
+2
kernel/context_tracking.c
···
198
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if (initialized)
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return;
200
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+
#ifdef CONFIG_HAVE_TIF_NOHZ
201
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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.
204
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*/
205
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set_tsk_thread_flag(&init_task, TIF_NOHZ);
207
+
#endif
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WARN_ON_ONCE(!tasklist_empty());
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initialized = true;