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From: Boqun Feng <boqun@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Catalin Marinas" <catalin.marinas@arm.com>,
	"Will Deacon" <will@kernel.org>,
	"Jonas Bonn" <jonas@southpole.se>,
	"Stefan Kristiansson" <stefan.kristiansson@saunalahti.fi>,
	"Stafford Horne" <shorne@gmail.com>,
	"Heiko Carstens" <hca@linux.ibm.com>,
	"Vasily Gorbik" <gor@linux.ibm.com>,
	"Alexander Gordeev" <agordeev@linux.ibm.com>,
	"Christian Borntraeger" <borntraeger@linux.ibm.com>,
	"Sven Schnelle" <svens@linux.ibm.com>,
	"Thomas Gleixner" <tglx@kernel.org>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Juri Lelli" <juri.lelli@redhat.com>,
	"Vincent Guittot" <vincent.guittot@linaro.org>,
	"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
	"Valentin Schneider" <vschneid@redhat.com>,
	"K Prateek Nayak" <kprateek.nayak@amd.com>,
	"Boqun Feng" <boqun@kernel.org>,
	"Waiman Long" <longman@redhat.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Miguel Ojeda" <ojeda@kernel.org>, "Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <lossin@kernel.org>,
	"Andreas Hindborg" <a.hindborg@kernel.org>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Trevor Gross" <tmgross@umich.edu>,
	"Danilo Krummrich" <dakr@kernel.org>,
	"Jinjie Ruan" <ruanjinjie@huawei.com>,
	"Ada Couprie Diaz" <ada.coupriediaz@arm.com>,
	"Lyude Paul" <lyude@redhat.com>,
	"Sohil Mehta" <sohil.mehta@intel.com>,
	"Pawan Gupta" <pawan.kumar.gupta@linux.intel.com>,
	"Xin Li (Intel)" <xin@zytor.com>,
	"Sean Christopherson" <seanjc@google.com>,
	"Nikunj A Dadhania" <nikunj@amd.com>,
	"Joel Fernandes" <joelagnelf@nvidia.com>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Randy Dunlap" <rdunlap@infradead.org>,
	"Yury Norov" <ynorov@nvidia.com>,
	"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
	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 09/11] sched: Avoid signed comparison of preempt_count() in __cant_migrate()
Date: Thu,  7 May 2026 21:21:09 -0700	[thread overview]
Message-ID: <20260508042111.24358-10-boqun@kernel.org> (raw)
In-Reply-To: <20260508042111.24358-1-boqun@kernel.org>

Currently preempt_count() is always a non-negative int on all archs
(PREEMPT_NEED_RESCHED archs will mask out the MSB when return
preempt_count()), hence the checking in __cant_migrate() is in fact just
checking whether preempt_count() is 0 or not. In a future change, we are
going to use all the 32 bits of preempt_count(), which would make
negative int values possible from preempt_count(). Therefore convert the
"> 0" comparison into a zero checking to prepare for the future change.
No functional changes are intended.

Signed-off-by: Boqun Feng <boqun@kernel.org>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 75dba7cc09bd..636e6a15f104 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9207,7 +9207,7 @@ void __cant_migrate(const char *file, int line)
 	if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
 		return;
 
-	if (preempt_count() > 0)
+	if (preempt_count())
 		return;
 
 	if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
-- 
2.50.1 (Apple Git-155)


  parent reply	other threads:[~2026-05-08  4:21 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-05-08  4:21 [PATCH 00/11] Refcounted interrupt disable and SpinLockIrq for rust (Part 1) Boqun Feng
2026-05-08  4:21 ` [PATCH 01/11] preempt: Introduce HARDIRQ_DISABLE_BITS Boqun Feng
2026-05-08  4:21 ` [PATCH 02/11] preempt: Track NMI nesting to separate per-CPU counter Boqun Feng
2026-05-08  4:21 ` [PATCH 03/11] preempt: Introduce __preempt_count_{sub, add}_return() Boqun Feng
2026-05-09 18:09   ` Heiko Carstens
2026-05-08  4:21 ` [PATCH 04/11] openrisc: Include <linux/cpumask.h> in smp.h Boqun Feng
2026-05-08  4:21 ` [PATCH 05/11] irq & spin_lock: Add counted interrupt disabling/enabling Boqun Feng
2026-05-08  4:21 ` [PATCH 06/11] irq: Add KUnit test for refcounted interrupt enable/disable Boqun Feng
2026-05-08  4:21 ` [PATCH 07/11] locking: Switch to _irq_{disable,enable}() variants in cleanup guards Boqun Feng
2026-05-08  4:21 ` [PATCH 08/11] sched: Remove the unused preempt_offset parameter of __cant_sleep() Boqun Feng
2026-05-08  4:21 ` Boqun Feng [this message]
2026-05-08  4:21 ` [PATCH 10/11] preempt: Introduce PREEMPT_COUNT_64BIT Boqun Feng
2026-05-08  4:21 ` [PATCH 11/11] arm64: sched/preempt: Enable PREEMPT_COUNT_64BIT Boqun Feng
2026-05-08  8:22   ` Mark Rutland
2026-05-08 14:48     ` Boqun Feng
2026-05-09 18:12 ` [PATCH 00/11] Refcounted interrupt disable and SpinLockIrq for rust (Part 1) Heiko Carstens
2026-05-09 18:21   ` Boqun Feng

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