From nobody Wed Nov 27 04:44:52 2024 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8568519308A; Sat, 12 Oct 2024 14:16:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728742571; cv=none; b=T2mLI2a54hk6JHLtcVfPwAKGgYpOjJJ8yYb5MymEwalYalO71IDc+HTw1zNK+vFnOucmbPu1xBwucw0ucQEwmpLaWXas8yJNiednHIieRNFk9Hv9j/AMcBtnam1mZcMM5N44ykz33IE6Er4vvxEmYbO3sDPZP6I+xl/+jaYmBNM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728742571; c=relaxed/simple; bh=0/RYzvGUFbsFfj1sMdP8Wd5qYESLnW6fb8beS5GdiHc=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=kdD+MfxGoK6jymZk49pRwqXsA6QNr8YAhoQAvBysAulfX5t3a4yNU2U+4Zcd7N7XnKYcdMqbflmHx0EcsoTsFVCztmOBODAwYWARhEGMzv7L5MSGbzXYOdGUP7QaqdM8UByIodbZtIKCRFRqwNRTDtZxt5ig8avTFHUPv9Z5atM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=f8ernEGr; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=xomZHxTv; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="f8ernEGr"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="xomZHxTv" Date: Sat, 12 Oct 2024 14:16:00 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1728742561; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=p1pXOBoxjzU9nr3rsWS4V0LQmNtm59zMFSsKrkGALt0=; b=f8ernEGripD1ounHBLUxcLPA7Oks5NdZaglzNRnmhyvcccxc+WUuF5frqJl4ITiZXhbClq jFsgazwWXhrnFT2lDMn5PzNL/qjuMlk8B2S4etrrqXCp09PbSUIFbEOgcHf5r+HExxuQFS lQ9Qm3zbDl+UBxAeQN2+DjEWytg7fgxUEOCxesWx9yS3hVi5aHl/ePlWyJMtAxXHrvUSQW +RzYhAqL/aZCSttA7dZpyd4J6qQOdfB8CbmzRxvoacxgClJ5C4NOTy2TBBd2cUkBKNh+vz 31c1fSrNp9cq+55MJd+ao7LS6OHx3Pa74kI8pq+h+MBvuiUwE9X31gb7qexh7w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1728742561; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=p1pXOBoxjzU9nr3rsWS4V0LQmNtm59zMFSsKrkGALt0=; b=xomZHxTvClWcz0pt7o3ThCLPtXIiF/lvjRyNdU3Q9FeXsSiiCapEtLRg3CnDuD9gef7xbb 4M7HtKzNcqC2itDQ== From: "tip-bot2 for Waiman Long" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] sched/core: Disable page allocation in task_tick_mm_cid() Cc: Waiman Long , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20241010014432.194742-1-longman@redhat.com> References: <20241010014432.194742-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <172874256094.1442.15152934978604510984.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 73ab05aa46b02d96509cb029a8d04fca7bbde8c7 Gitweb: https://git.kernel.org/tip/73ab05aa46b02d96509cb029a8d04fca7= bbde8c7 Author: Waiman Long AuthorDate: Wed, 09 Oct 2024 21:44:32 -04:00 Committer: Peter Zijlstra CommitterDate: Fri, 11 Oct 2024 10:49:32 +02:00 sched/core: Disable page allocation in task_tick_mm_cid() With KASAN and PREEMPT_RT enabled, calling task_work_add() in task_tick_mm_cid() may cause the following splat. [ 63.696416] BUG: sleeping function called from invalid context at kernel= /locking/spinlock_rt.c:48 [ 63.696416] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 610, = name: modprobe [ 63.696416] preempt_count: 10001, expected: 0 [ 63.696416] RCU nest depth: 1, expected: 1 This problem is caused by the following call trace. sched_tick() [ acquire rq->__lock ] -> task_tick_mm_cid() -> task_work_add() -> __kasan_record_aux_stack() -> kasan_save_stack() -> stack_depot_save_flags() -> alloc_pages_mpol_noprof() -> __alloc_pages_noprof() -> get_page_from_freelist() -> rmqueue() -> rmqueue_pcplist() -> __rmqueue_pcplist() -> rmqueue_bulk() -> rt_spin_lock() The rq lock is a raw_spinlock_t. We can't sleep while holding it. IOW, we can't call alloc_pages() in stack_depot_save_flags(). The task_tick_mm_cid() function with its task_work_add() call was introduced by commit 223baf9d17f2 ("sched: Fix performance regression introduced by mm_cid") in v6.4 kernel. Fortunately, there is a kasan_record_aux_stack_noalloc() variant that calls stack_depot_save_flags() while not allowing it to allocate new pages. To allow task_tick_mm_cid() to use task_work without page allocation, a new TWAF_NO_ALLOC flag is added to enable calling kasan_record_aux_stack_noalloc() instead of kasan_record_aux_stack() if set. The task_tick_mm_cid() function is modified to add this new flag. The possible downside is the missing stack trace in a KASAN report due to new page allocation required when task_work_add_noallloc() is called which should be rare. Fixes: 223baf9d17f2 ("sched: Fix performance regression introduced by mm_ci= d") Signed-off-by: Waiman Long Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20241010014432.194742-1-longman@redhat.com --- include/linux/task_work.h | 5 ++++- kernel/sched/core.c | 4 +++- kernel/task_work.c | 15 +++++++++++++-- 3 files changed, 20 insertions(+), 4 deletions(-) diff --git a/include/linux/task_work.h b/include/linux/task_work.h index cf5e7e8..2964171 100644 --- a/include/linux/task_work.h +++ b/include/linux/task_work.h @@ -14,11 +14,14 @@ init_task_work(struct callback_head *twork, task_work_f= unc_t func) } =20 enum task_work_notify_mode { - TWA_NONE, + TWA_NONE =3D 0, TWA_RESUME, TWA_SIGNAL, TWA_SIGNAL_NO_IPI, TWA_NMI_CURRENT, + + TWA_FLAGS =3D 0xff00, + TWAF_NO_ALLOC =3D 0x0100, }; =20 static inline bool task_work_pending(struct task_struct *task) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 43e453a..0259301 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -10458,7 +10458,9 @@ void task_tick_mm_cid(struct rq *rq, struct task_st= ruct *curr) return; if (time_before(now, READ_ONCE(curr->mm->mm_cid_next_scan))) return; - task_work_add(curr, work, TWA_RESUME); + + /* No page allocation under rq lock */ + task_work_add(curr, work, TWA_RESUME | TWAF_NO_ALLOC); } =20 void sched_mm_cid_exit_signals(struct task_struct *t) diff --git a/kernel/task_work.c b/kernel/task_work.c index 5d14d63..c969f1f 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -55,15 +55,26 @@ int task_work_add(struct task_struct *task, struct call= back_head *work, enum task_work_notify_mode notify) { struct callback_head *head; + int flags =3D notify & TWA_FLAGS; =20 + notify &=3D ~TWA_FLAGS; if (notify =3D=3D TWA_NMI_CURRENT) { if (WARN_ON_ONCE(task !=3D current)) return -EINVAL; if (!IS_ENABLED(CONFIG_IRQ_WORK)) return -EINVAL; } else { - /* record the work call stack in order to print it in KASAN reports */ - kasan_record_aux_stack(work); + /* + * Record the work call stack in order to print it in KASAN + * reports. + * + * Note that stack allocation can fail if TWAF_NO_ALLOC flag + * is set and new page is needed to expand the stack buffer. + */ + if (flags & TWAF_NO_ALLOC) + kasan_record_aux_stack_noalloc(work); + else + kasan_record_aux_stack(work); } =20 head =3D READ_ONCE(task->task_works);