linux-kernel - [PATCH] sched: Add _TIF_NEED_RESCHED_LAZY to __resched

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20250928151421.60919-1-jemmywong512@gmail.com>
Date: Sun, 28 Sep 2025 23:14:21 +0800
From: Jemmy Wong <jemmywong512@...il.com>
To: Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andy Lutomirski <luto@...nel.org>,
	Kees Cook <kees@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Jemmy Wong <jemmywong512@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] sched: Add _TIF_NEED_RESCHED_LAZY to __resched_curr check

The TIF_NEED_RESCHED_LAZY flag can be set multiple times in a single
call path. For example:

entity_tick()
    update_curr(cfs_rq);
        resched_curr_lazy(rq);
    resched_curr_lazy(rq_of(cfs_rq));

Add a check in resched_curr_lazy() to return early if the flag is
already set, avoiding redundant operations.

Signed-off-by: Jemmy Wong <jemmywong512@...il.com>

---
 include/linux/sched.h       | 2 +-
 include/linux/thread_info.h | 2 ++
 kernel/entry/common.c       | 2 +-
 kernel/entry/kvm.c          | 2 +-
 kernel/sched/core.c         | 2 +-
 5 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e4ce0a76831e..5946434b2dc4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2041,7 +2041,7 @@ static inline void set_tsk_need_resched(struct task_struct *tsk)

 static inline void clear_tsk_need_resched(struct task_struct *tsk)
 {
-	atomic_long_andnot(_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY,
+	atomic_long_andnot(_TIF_NEED_RESCHED_MUSK,
 			  (atomic_long_t *)&task_thread_info(tsk)->flags);
 }

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index dd925d84fa46..a7512ab612ad 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -67,6 +67,8 @@ enum syscall_work_bit {
 #define _TIF_NEED_RESCHED_LAZY _TIF_NEED_RESCHED
 #endif

+#define _TIF_NEED_RESCHED_MUSK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
+
 #ifdef __KERNEL__

 #ifndef arch_set_restart_data
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 408d28b5179d..ac6eff43d07e 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -27,7 +27,7 @@ __always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs,

 		local_irq_enable_exit_to_user(ti_work);

-		if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
+		if (ti_work & _TIF_NEED_RESCHED_MUSK)
 			schedule();

 		if (ti_work & _TIF_UPROBE)
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index 8485f63863af..cacb24f0fc86 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -13,7 +13,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
 			return -EINTR;
 		}

-		if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
+		if (ti_work & _TIF_NEED_RESCHED_MUSK)
 			schedule();

 		if (ti_work & _TIF_NOTIFY_RESUME)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ccba6fc3c3fe..15bf4b132153 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1108,7 +1108,7 @@ static void __resched_curr(struct rq *rq, int tif)
 	if (is_idle_task(curr) && tif == TIF_NEED_RESCHED_LAZY)
 		tif = TIF_NEED_RESCHED;

-	if (cti->flags & ((1 << tif) | _TIF_NEED_RESCHED))
+	if (cti->flags & ((1 << tif) | _TIF_NEED_RESCHED_MUSK))
 		return;

 	cpu = cpu_of(rq);
--
2.50.1 (Apple Git-155)