From: Boqun Feng <boqun@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Ingo Molnar" <mingo@kernel.org>, "Will Deacon" <will@kernel.org>,
"Boqun Feng" <boqun@kernel.org>,
"Waiman Long" <longman@redhat.com>, "Gary Guo" <gary@garyguo.net>,
"Alice Ryhl" <aliceryhl@google.com>,
"Lyude Paul" <lyude@redhat.com>,
"Daniel Almeida" <daniel.almeida@collabora.com>,
"Onur Özkan" <work@onurozkan.dev>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Danilo Krummrich" <dakr@kernel.org>,
linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org
Subject: [PATCH v4 09/17] sched: Avoid signed comparison of preempt_count() in __cant_migrate()
Date: Tue, 4 Aug 2026 09:14:31 -0700 [thread overview]
Message-ID: <20260804161447.84806-10-boqun@kernel.org> (raw)
In-Reply-To: <20260804161447.84806-1-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 returning
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 check 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 aa116daf21bd..9b3f1764fa9e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9241,7 +9241,7 @@ 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)
next prev parent reply other threads:[~2026-08-04 16:15 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-04 16:14 [PATCH v4 00/17] Refcounted interrupt disable and SpinLockIrq for Rust Boqun Feng
2026-08-04 16:14 ` [PATCH v4 01/17] preempt: Track NMI nesting to separate per-CPU counter Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Joel Fernandes
2026-08-04 16:14 ` [PATCH v4 02/17] preempt: Introduce HARDIRQ_DISABLE_BITS Boqun Feng
2026-08-05 6:31 ` Peter Zijlstra
2026-08-05 6:59 ` Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2026-08-04 16:14 ` [PATCH v4 03/17] preempt: Introduce __preempt_count_{sub,add}_return() Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2026-08-04 16:14 ` [PATCH v4 04/17] openrisc: Include <linux/cpumask.h> in smp.h Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Lyude Paul
2026-08-04 16:14 ` [PATCH v4 05/17] irq & spin_lock: Add counted interrupt disabling/enabling Boqun Feng
2026-08-04 18:20 ` Boqun Feng
2026-08-04 18:26 ` [PATCH v4.1 " Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2026-08-10 8:57 ` [tip: locking/core] irq,spin_lock: " tip-bot2 for Boqun Feng
2026-08-04 20:51 ` [PATCH v4 05/17] irq & spin_lock: " Shrikanth Hegde
2026-08-04 21:08 ` Boqun Feng
2026-08-05 6:36 ` Peter Zijlstra
2026-08-05 7:07 ` Boqun Feng
2026-08-05 7:09 ` Shrikanth Hegde
2026-08-05 7:19 ` Boqun Feng
2026-08-05 13:53 ` Boqun Feng
2026-08-05 14:10 ` Shrikanth Hegde
2026-08-05 14:20 ` Boqun Feng
2026-08-05 14:56 ` Shrikanth Hegde
2026-08-05 15:11 ` Boqun Feng
2026-08-05 16:53 ` Shrikanth Hegde
2026-08-05 17:38 ` Boqun Feng
2026-08-05 18:07 ` Boqun Feng
2026-08-04 16:14 ` [PATCH v4 06/17] irq: Add KUnit test for refcounted interrupt enable/disable Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Lyude Paul
2026-08-10 8:57 ` tip-bot2 for Lyude Paul
2026-08-04 16:14 ` [PATCH v4 07/17] locking: Switch to _irq_{disable,enable}() variants in cleanup guards Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2026-08-10 8:57 ` tip-bot2 for Boqun Feng
2026-08-04 16:14 ` [PATCH v4 08/17] sched: Remove the unused preempt_offset parameter of __cant_sleep() Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2026-08-10 8:57 ` tip-bot2 for Boqun Feng
2026-08-04 16:14 ` Boqun Feng [this message]
2026-08-08 20:48 ` [tip: locking/core] sched: Avoid signed comparison of preempt_count() in __cant_migrate() tip-bot2 for Boqun Feng
2026-08-10 8:57 ` tip-bot2 for Boqun Feng
2026-08-04 16:14 ` [PATCH v4 10/17] preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS Boqun Feng
2026-08-04 20:11 ` Shrikanth Hegde
2026-08-05 6:54 ` Boqun Feng
2026-08-05 7:15 ` Shrikanth Hegde
2026-08-05 7:27 ` Boqun Feng
2026-08-06 0:58 ` Boqun Feng
2026-08-04 21:09 ` Shrikanth Hegde
2026-08-04 23:14 ` Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2026-08-10 8:57 ` tip-bot2 for Boqun Feng
2026-08-04 16:14 ` [PATCH v4 11/17] arm64: sched/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS Boqun Feng
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Boqun Feng
2026-08-10 8:57 ` tip-bot2 for Boqun Feng
2026-08-04 16:14 ` [PATCH v4 12/17] s390/preempt: " Boqun Feng
2026-08-04 20:27 ` Shrikanth Hegde
2026-08-05 9:42 ` Peter Zijlstra
2026-08-05 12:37 ` Shrikanth Hegde
2026-08-08 20:48 ` [tip: locking/core] " tip-bot2 for Heiko Carstens
2026-08-10 8:57 ` tip-bot2 for Heiko Carstens
2026-08-04 16:14 ` [PATCH v4 13/17] rust: Introduce interrupt module Boqun Feng
2026-08-04 16:14 ` [PATCH v4 14/17] rust: helper: Add spin_{un,}lock_irq_{enable,disable}() helpers Boqun Feng
2026-08-04 16:14 ` [PATCH v4 15/17] rust: sync: Use super::* in spinlock.rs Boqun Feng
2026-08-04 16:14 ` [PATCH v4 16/17] rust: sync: Add SpinLockIrq Boqun Feng
2026-08-04 16:14 ` [PATCH v4 17/17] rust: sync: Introduce SpinLockIrq::lock_with() and friends Boqun Feng
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