From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793207162; b=rXIRA1/0+hm9LYFD27G2A9lGU3XgnmT66z+mjVWnk72S+oztpa/M1BwHXwW+gzRZ0c+1 z69Ycyv90D5ZaIxMsnwzwJXe7+8qAux4o8hErpnXFdZFdmp9q7Hu/fQo5s7Yu6nSHwVCp EpuvrED6r0p6wPGiDfB9TzRyhUUmd+nJyduRoev4qw8omJEpArNQr6IGd2SREw5MYSX/Q XM/7CgB1COV6ptxXNC2+UkAdqmxoz6lPYzMAsfkX28X+NawBhiOTHapjft4wqo5NaPpv4 Pc/9X20+AV1gzkFU7mwZZK2wSta2bR975xZd71g6lcD/q2o8ELwOvbE7ZIWWeHq+O+w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793207162; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=5DSzloH2Yqil2PllG4BcS7fWixJtF9LGJWq9RePWD8U=; b=Q8e/aUGNdQZnVSczpInzJ/9SgGujFjIbx/9zqDSpNGO+jtZsFXtfAkcPxx9kOjabiWYH ztlpodQ2ncwfBYPmUuzo+AuNfk2MCFtiLnoL1tJlcCmNHNM8dcKzW0sHrPB9MeMEzpzZn 9zl7iDcgzhk7udMvP9vu0PbjKYQnmnGIr36doSYeHlBRc0QEVybeOGe9UpHOqVQMeiIPz UQvGf9wZ4NQTWOmzRY6HavOuwVPqKaxRH/DbN9bA9/3ala0p2SZ8wZhxgndGhEIkKqu4z ewACSYBd4xjsw5dHWtcAgucKtkYXLlwp/es2uttywepRs2LkL9aizzp0kXbIgtddAMA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=yGXO0eEG; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7C74606A31F; Wed, 28 Oct 2026 17:06:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=yGXO0eEG Received: by smtp.kernel.org (Postfix) with ESMTPSA id 443471F01828; Wed, 28 Oct 2026 17:06:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793207161; bh=5DSzloH2Yqil2PllG4BcS7fWixJtF9LGJWq9RePWD8U=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=yGXO0eEGxzpHHtaoIbb3d3F5AJJqX9qrwb5iyh4sVWI2tl7Tk4PZxcyvHO7GQJYui 3tuBlePtf4PeqghOfpl9dSoUDzoAVMy5OfGs0CA/eRq6w0w7JL4MZJGzaLFLPBbXpp PciHB8HJEjvxW0Kq9sZq/SlnHrw8/5uyIimBj17g= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Andrea Righi , Kuba Piecuch , Tejun Heo , Cheng-Yang Chou , Sasha Levin Subject: [PATCH 7.2 01/88] sched_ext: Wait for SCX_OPSS_DISPATCHING before moving tasks off DSQs Date: Wed, 28 Oct 2026 17:59:09 +0100 Message-ID: <20261028165942.145347695@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165942.107695352@linuxfoundation.org> References: <20261028165942.107695352@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kuba Piecuch [ Upstream commit 2935062be77113c1c4565ca9d0c72180449aafee ] A task can be found on a non-local DSQ while the CPU which dispatched it is still running ops.dequeue() and hasn't cleared SCX_OPSS_DISPATCHING. The DSQ consume and move paths don't wait for the dispatch to finish and can operate on the task concurrently with the dispatcher. Call scx_wait_dispatching() in scx_move_local_task_to_local_dsq(), unlink_dsq_and_switch_rq_lock() and move_task_between_dsqs() before they operate on the task. In scx_move_local_task_to_local_dsq(), wait before scx_resolve_local_dsq() as it may update p->scx.flags. Fixes: ebf1ccff79c4 ("sched_ext: Fix ops.dequeue() semantics") Fixes: cb86607ada73 ("sched_ext: Don't run ops.dequeue() with a DSQ lock held") Cc: stable@vger.kernel.org # v7.1+ Reviewed-by: Andrea Righi Assisted-by: Claude:claude-opus-5.5 Signed-off-by: Kuba Piecuch Signed-off-by: Tejun Heo [ Inlined scx_wait_dispatching(), which 7.2.y doesn't have, into move_local_task_to_local_dsq(), unlink_dsq_and_lock_src_rq() and move_task_between_dsqs(), as was done for the reenqueue paths in 7.2.y. 7.2.y has no scx_resolve_local_dsq(), so move_local_task_to_local_dsq() waits before linking the task. ] Signed-off-by: Cheng-Yang Chou Signed-off-by: Sasha Levin --- kernel/sched/ext/ext.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 3ee16f7f22cde..c117cf172dfca 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -2292,6 +2292,8 @@ static void move_local_task_to_local_dsq(struct scx_sched *sch, lockdep_assert_rq_held(dst_rq); WARN_ON_ONCE(p->scx.holding_cpu >= 0); + if (unlikely(atomic_long_read_acquire(&p->scx.ops_state) == SCX_OPSS_DISPATCHING)) + wait_ops_state(p, SCX_OPSS_DISPATCHING); if (enq_flags & (SCX_ENQ_HEAD | SCX_ENQ_PREEMPT)) list_add(&p->scx.dsq_list.node, &dst_dsq->list); @@ -2462,8 +2464,13 @@ static bool unlink_dsq_and_lock_src_rq(struct task_struct *p, raw_spin_rq_lock(src_rq); /* task_rq couldn't have changed if we're still the holding cpu */ - return likely(p->scx.holding_cpu == cpu) && - !WARN_ON_ONCE(src_rq != task_rq(p)); + if (likely(p->scx.holding_cpu == cpu) && !WARN_ON_ONCE(src_rq != task_rq(p))) { + if (unlikely(atomic_long_read_acquire(&p->scx.ops_state) == SCX_OPSS_DISPATCHING)) + wait_ops_state(p, SCX_OPSS_DISPATCHING); + return true; + } + + return false; } static bool consume_remote_task(struct rq *this_rq, @@ -2511,6 +2518,9 @@ static struct rq *move_task_between_dsqs(struct scx_sched *sch, lockdep_assert_held(&src_dsq->lock); lockdep_assert_rq_held(src_rq); + if (unlikely(atomic_long_read_acquire(&p->scx.ops_state) == SCX_OPSS_DISPATCHING)) + wait_ops_state(p, SCX_OPSS_DISPATCHING); + if (dst_dsq->id == SCX_DSQ_LOCAL) { dst_rq = container_of(dst_dsq, struct rq, scx.local_dsq); if (src_rq != dst_rq && -- 2.53.0