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Peter Anvin" , Arnd Bergmann , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Boqun Feng , Waiman Long , Andrew Morton , Miguel Ojeda , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Jinjie Ruan , Ada Couprie Diaz , Lyude Paul , Sohil Mehta , Pawan Gupta , "Xin Li (Intel)" , Sean Christopherson , Nikunj A Dadhania , Joel Fernandes , Andy Shevchenko , Randy Dunlap , Yury Norov , Sebastian Andrzej Siewior , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-openrisc@vger.kernel.org, linux-s390@vger.kernel.org, linux-arch@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: [PATCH 11/11] arm64: sched/preempt: Enable PREEMPT_COUNT_64BIT Date: Thu, 7 May 2026 21:21:11 -0700 Message-ID: <20260508042111.24358-12-boqun@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260508042111.24358-1-boqun@kernel.org> References: <20260508042111.24358-1-boqun@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ARM64 already uses 64bit preempt count and the need reschedule bit is maintained in a separate 32bit than the preempt count. Therefore preempt count has enough bits to represent 16 level of NMI nesting, hence enable it for ARM64. This saves a per-CPU variable and additional instructions in the NMI path. Signed-off-by: Boqun Feng --- arch/arm64/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index fe60738e5943..1ed5173872fc 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -248,6 +248,7 @@ config ARM64 select PCI_SYSCALL if PCI select POWER_RESET select POWER_SUPPLY + select PREEMPT_COUNT_64BIT select SPARSE_IRQ select SWIOTLB select SYSCTL_EXCEPTION_TRACE -- 2.50.1 (Apple Git-155)