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| author | Frederic Weisbecker <frederic@kernel.org> | 2020-01-27 16:41:52 +0100 |
|---|---|---|
| committer | Frederic Weisbecker <frederic@kernel.org> | 2020-02-14 16:05:04 +0100 |
| commit | 490f561b783dac2c4825e288e6dbbf83481eea34 (patch) | |
| tree | 9d51328accd11ec6eafd8e1cc0e0a150c451b764 /arch/Kconfig | |
| parent | 7c805795307b40af50a45b7db44dd09ac1700947 (diff) | |
| download | lwn-490f561b783dac2c4825e288e6dbbf83481eea34.tar.gz lwn-490f561b783dac2c4825e288e6dbbf83481eea34.zip | |
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@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/Kconfig')
| -rw-r--r-- | arch/Kconfig | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 98de654b79b3..dbf420a9f87b 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 |