linux-kernel - [PATCH sched_ext/for-6.15] sched_ext: idle: Fix scx_bpf_pick_any_cpu

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>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250225093742.51597-1-arighi@nvidia.com>
Date: Tue, 25 Feb 2025 10:37:42 +0100
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>,
	David Vernet <void@...ifault.com>,
	Changwoo Min <changwoo@...lia.com>
Cc: Yury Norov <yury.norov@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH sched_ext/for-6.15] sched_ext: idle: Fix scx_bpf_pick_any_cpu_node() behavior

When %SCX_PICK_IDLE_IN_NODE is specified, scx_bpf_pick_any_cpu_node()
should always return a CPU from the specified node, regardless of its
idle state.

Also clarify this logic in the function documentation.

Fixes: 01059219b0cfd ("sched_ext: idle: Introduce node-aware idle cpu kfunc helpers")
Signed-off-by: Andrea Righi <arighi@...dia.com>
---
 kernel/sched/ext_idle.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c
index 759a06774b5b3..dc40e0baf77c5 100644
--- a/kernel/sched/ext_idle.c
+++ b/kernel/sched/ext_idle.c
@@ -1029,8 +1029,9 @@ __bpf_kfunc s32 scx_bpf_pick_idle_cpu(const struct cpumask *cpus_allowed,
  * empty.
  *
  * The search starts from @node and proceeds to other online NUMA nodes in
- * order of increasing distance (unless SCX_PICK_IDLE_IN_NODE is specified,
- * in which case the search is limited to the target @node).
+ * order of increasing distance (unless %SCX_PICK_IDLE_IN_NODE is specified,
+ * in which case the search is limited to the target @node, regardless of
+ * the CPU idle state).
  *
  * If ops.update_idle() is implemented and %SCX_OPS_KEEP_BUILTIN_IDLE is not
  * set, this function can't tell which CPUs are idle and will always pick any
@@ -1049,7 +1050,10 @@ __bpf_kfunc s32 scx_bpf_pick_any_cpu_node(const struct cpumask *cpus_allowed,
 	if (cpu >= 0)
 		return cpu;
 
-	cpu = cpumask_any_distribute(cpus_allowed);
+	if (flags & SCX_PICK_IDLE_IN_NODE)
+		cpu = cpumask_any_and_distribute(cpumask_of_node(node), cpus_allowed);
+	else
+		cpu = cpumask_any_distribute(cpus_allowed);
 	if (cpu < nr_cpu_ids)
 		return cpu;
 	else
-- 
2.48.1