linux-kernel - [PATCHSET sched_ext/for-6.19] sched_ext: Fix SCX_KICK

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: <20251021210354.89570-1-tj@kernel.org>
Date: Tue, 21 Oct 2025 11:03:52 -1000
From: Tejun Heo <tj@...nel.org>
To: David Vernet <void@...ifault.com>,
	Andrea Righi <arighi@...dia.com>,
	Changwoo Min <changwoo@...lia.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev,
	bpf@...r.kernel.org
Subject: [PATCHSET sched_ext/for-6.19] sched_ext: Fix SCX_KICK_WAIT reliability

SCX_KICK_WAIT is used to synchronously wait for a target CPU to complete a
reschedule, which is needed for implementing operations like core scheduling.
This broke when scx_next_task_picked() was replaced with switch_class() in
commit b999e365c298, because the sequence counter increment that SCX_KICK_WAIT
depends on was no longer reliably called.

This patchset fixes the regression by moving the sequence counter update to
put_prev_task_scx() and refining the semantics to work correctly with the
updated scheduler structure. The first patch adds a prerequisite check to
skip kicking CPUs running higher sched classes, which SCX has no control over.

Based on sched_ext/for-6.19 (2dbbdeda77a6).

 0001 sched_ext: Don't kick CPUs running higher classes
 0002 sched_ext: Fix SCX_KICK_WAIT to work reliably

Git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-fix-kick_wait

 kernel/sched/ext.c          | 42 ++++++++++++++++++++++++++----------------
 kernel/sched/ext_internal.h |  6 ++++--
 2 files changed, 30 insertions(+), 18 deletions(-)
--
tejun