From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 99BCD1D9663 for ; Tue, 25 Aug 2026 01:33:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787621635; cv=none; b=Jzza7EBQxPo8xFvD0blFB12CNVim6D2MCD3Ml3dj7XWlyR7r/v7torVd8Ck5xOHucBikIapqMN/dyizFVyN7VOV6uq7lAaSiVVq3daxpfPOCvIHjYl7ezGZKxlwzuDjf8NpAqcAOL2rk8D+IzmBiEUklzmyIJ5VxrTSAgK3aEOY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787621635; c=relaxed/simple; bh=4GIytygZwgjwiikBEPYWO23nMPvFqfeVKVlDdW5N83s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=pvwmpMmTc9B2qbxIJ6814hsAt+Wwug/Qo3WANk5ZfDpmnpHnCgAgXgUmxHOzytvnmG67y9XonQc0xzDgYBKWAv9peZZ0APCTdPnRmW86+gODboiYahXIVWunQGqhxfB/smNBL1PTMKIq94tfvC3obF/5PuvoiOCtd657Fzf/0xk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CGeBSPgg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CGeBSPgg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 346861F00A3D; Tue, 25 Aug 2026 01:33:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787621634; bh=nzqFG640zcQdBvIMsN2BS9oxCKAWvO230Az1GaunuJ0=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=CGeBSPggZaAxIN0gVSVMS4X5vgmu+/k6XsFVtcHvW4IblVIniiteUTSqkoZkS7Wzb 1dkBeiZCrTj/MQorlzlJvPjvF/+ataMR5/PKQdBV6z6FSvMplV0F9yFHsMtdsjwQ/3 nCCdMxCNculy3oMH/+gJnUUMgTeaHlfXxGhD1a/V6hao7lvvNXrmk4edwNVEA9GJit iohINXVnV6VxNBRFITNLnnI/bHklLzkIHqwTxAB+nZ8Lxgl0/KDeJts57hrF7n7HKH M/fjHN4P1qMfY9ptSau83IjOmiT+KWF2d9kL4RERiGq36/8yYqkUPO4OJUXmgF8tFt tJkcM7jl3B3iw== Received: from phl-compute-06.internal (phl-compute-06.internal [10.202.2.46]) by mailfauth.phl.internal (Postfix) with ESMTP id 40F83F40067; Mon, 24 Aug 2026 21:33:53 -0400 (EDT) Received: from phl-frontend-04 ([10.202.2.163]) by phl-compute-06.internal (MEProxy); Mon, 24 Aug 2026 21:33:53 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTE3mti1OEQwfFt4tMosLVus51WB1FvjrsD8hkhrWpdaQ2I/SyJCpG8VUMwithGrlQ YTOG2EWot+MLHIOIJgZnAnY9ovB4ztE7ClwrC3viFDg91rfxd0Km1EGogkxrpGpJqH/He1 X65tMwSG7/php/4LkJF/CSPtqCalGZoda4pWemeP/pXAZ+jppBRawpQbzb9vgSV/SgsepD /kfIYSeyzcjxLdM0SZp9U2TQlCm7W3DV/24W8EgpC50qwwaqF5/TlzlFQ5A0cnoyp+XywK rS4WwvwMX776m61zibXupB8tSL2ax44NFfdIXWoR8BC4z1a3u3//GIB+NFnUGfmTjOQ7HZ VFR/7rGEyuqaeKceTYb4grrnpjtO39fkcfrMH3y5m/35wEu9rH1ji6Tiw+vCKtCziXLfU5 BwA+q0n83Iup9DNsC8QYrnu3rM8Jo71/+/vYckgaJseN1Pd3i+rAQIphQoZ2kiTE164d4x h2IhFjdxNC/buLPas40hqYUUc6fc/WLrzlO7IZav6t2YgMBngvnwlGDIoB290adlSc4fYu U4VKJDllEIe713pi4bQ349mButgWmxiLj/tCctHuVRFG5kDHVwJa24wVKwEf0qw7d325H7 JcGlK6BoJHUXDyVqckrHIEvrsy7fnuDYqZx17MdlEcvpv7WukBWd0nKJDQyg X-ME-Proxy: Feedback-ID: i8dbe485b:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 24 Aug 2026 21:33:52 -0400 (EDT) Date: Mon, 24 Aug 2026 18:33:51 -0700 From: Boqun Feng To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, x86@kernel.org, Thomas Gleixner Subject: Re: [PATCH] locking: Revert switching guards to _irq_{disable,enable}() Message-ID: References: <20260804161447.84806-8-boqun@kernel.org> <178635226387.442315.3868294476114711805.tip-bot2@tip-bot2> <20260824104704.GA4121339@noisy.programming.kicks-ass.net> <20260824105523.GA4121620@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260824105523.GA4121620@noisy.programming.kicks-ass.net> On Mon, Aug 24, 2026 at 12:55:23PM +0200, Peter Zijlstra wrote: > > While the guards are properly nested, not all wrapped code is nice, as already > highlighted by that fair.c hunk. > > Syzbot found another instance of this pattern in posix_timer_delete(), which > does spin_unlock_irq()+spin_lock_irq() inside scoped_guard(spinlock_irq). > Combined with this patch, that goes sideways most spectacular. > > Undo this change, until we've developed stronger tools / debug for such issues. > Mainly hand-waving, but if we make _irq(), irqsave(), _disable() __acquires() different contexts, we may be able to catch these issues at compile time. I will explore a bit on this. > Signed-off-by: Peter Zijlstra (Intel) Acked-by: Boqun Feng Regards, Boqun > --- > include/linux/spinlock.h | 26 ++++++++++++++------------ > kernel/sched/fair.c | 12 ++++++------ > 2 files changed, 20 insertions(+), 18 deletions(-) > > --- a/include/linux/spinlock.h > +++ b/include/linux/spinlock.h > @@ -572,12 +572,12 @@ DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_ > #define class_raw_spinlock_nested_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_nested, _T) > > DEFINE_LOCK_GUARD_1(raw_spinlock_irq, raw_spinlock_t, > - raw_spin_lock_irq_disable(_T->lock), > - raw_spin_unlock_irq_enable(_T->lock)) > + raw_spin_lock_irq(_T->lock), > + raw_spin_unlock_irq(_T->lock)) > DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_irq, __acquires(_T), __releases(*(raw_spinlock_t **)_T)) > #define class_raw_spinlock_irq_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_irq, _T) > > -DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq_disable(_T->lock)) > +DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irq, _try, raw_spin_trylock_irq(_T->lock)) > DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_irq_try, __acquires(_T), __releases(*(raw_spinlock_t **)_T)) > #define class_raw_spinlock_irq_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_irq_try, _T) > > @@ -592,13 +592,14 @@ DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_ > #define class_raw_spinlock_bh_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_bh_try, _T) > > DEFINE_LOCK_GUARD_1(raw_spinlock_irqsave, raw_spinlock_t, > - raw_spin_lock_irq_disable(_T->lock), > - raw_spin_unlock_irq_enable(_T->lock)) > + raw_spin_lock_irqsave(_T->lock, _T->flags), > + raw_spin_unlock_irqrestore(_T->lock, _T->flags), > + unsigned long flags) > DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_irqsave, __acquires(_T), __releases(*(raw_spinlock_t **)_T)) > #define class_raw_spinlock_irqsave_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_irqsave, _T) > > DEFINE_LOCK_GUARD_1_COND(raw_spinlock_irqsave, _try, > - raw_spin_trylock_irq_disable(_T->lock)) > + raw_spin_trylock_irqsave(_T->lock, _T->flags)) > DECLARE_LOCK_GUARD_1_ATTRS(raw_spinlock_irqsave_try, __acquires(_T), __releases(*(raw_spinlock_t **)_T)) > #define class_raw_spinlock_irqsave_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(raw_spinlock_irqsave_try, _T) > > @@ -617,13 +618,13 @@ DECLARE_LOCK_GUARD_1_ATTRS(spinlock_try, > #define class_spinlock_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_try, _T) > > DEFINE_LOCK_GUARD_1(spinlock_irq, spinlock_t, > - spin_lock_irq_disable(_T->lock), > - spin_unlock_irq_enable(_T->lock)) > + spin_lock_irq(_T->lock), > + spin_unlock_irq(_T->lock)) > DECLARE_LOCK_GUARD_1_ATTRS(spinlock_irq, __acquires(_T), __releases(*(spinlock_t **)_T)) > #define class_spinlock_irq_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_irq, _T) > > DEFINE_LOCK_GUARD_1_COND(spinlock_irq, _try, > - spin_trylock_irq_disable(_T->lock)) > + spin_trylock_irq(_T->lock)) > DECLARE_LOCK_GUARD_1_ATTRS(spinlock_irq_try, __acquires(_T), __releases(*(spinlock_t **)_T)) > #define class_spinlock_irq_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_irq_try, _T) > > @@ -639,13 +640,14 @@ DECLARE_LOCK_GUARD_1_ATTRS(spinlock_bh_t > #define class_spinlock_bh_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_bh_try, _T) > > DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t, > - spin_lock_irq_disable(_T->lock), > - spin_unlock_irq_enable(_T->lock)) > + spin_lock_irqsave(_T->lock, _T->flags), > + spin_unlock_irqrestore(_T->lock, _T->flags), > + unsigned long flags) > DECLARE_LOCK_GUARD_1_ATTRS(spinlock_irqsave, __acquires(_T), __releases(*(spinlock_t **)_T)) > #define class_spinlock_irqsave_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_irqsave, _T) > > DEFINE_LOCK_GUARD_1_COND(spinlock_irqsave, _try, > - spin_trylock_irq_disable(_T->lock)) > + spin_trylock_irqsave(_T->lock, _T->flags)) > DECLARE_LOCK_GUARD_1_ATTRS(spinlock_irqsave_try, __acquires(_T), __releases(*(spinlock_t **)_T)) > #define class_spinlock_irqsave_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(spinlock_irqsave_try, _T) > > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -7253,7 +7253,7 @@ static bool distribute_cfs_runtime(struc > * period the timer is deactivated until scheduling resumes; cfs_b->idle is > * used to track this state. > */ > -static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) > +static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags) > __must_hold(&cfs_b->lock) > { > int throttled; > @@ -7288,10 +7288,10 @@ static int do_sched_cfs_period_timer(str > * This check is repeated as we release cfs_b->lock while we unthrottle. > */ > while (throttled && cfs_b->runtime > 0) { > - raw_spin_unlock_irq_enable(&cfs_b->lock); > + raw_spin_unlock_irqrestore(&cfs_b->lock, flags); > /* we can't nest cfs_b->lock while distributing bandwidth */ > throttled = distribute_cfs_runtime(cfs_b); > - raw_spin_lock_irq_disable(&cfs_b->lock); > + raw_spin_lock_irqsave(&cfs_b->lock, flags); > } > > /* > @@ -7399,7 +7399,7 @@ static __always_inline void return_cfs_r > static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) > { > /* confirm we're still not at a refresh boundary */ > - scoped_guard(raw_spinlock_irq, &cfs_b->lock) { > + scoped_guard(raw_spinlock_irqsave, &cfs_b->lock) { > u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); > > cfs_b->slack_started = false; > @@ -7484,14 +7484,14 @@ static enum hrtimer_restart sched_cfs_pe > int idle = 0; > int count = 0; > > - guard(raw_spinlock_irq)(&cfs_b->lock); > + CLASS(raw_spinlock_irqsave, cfsb_guard)(&cfs_b->lock); > > for (;;) { > overrun = hrtimer_forward_now(timer, cfs_b->period); > if (!overrun) > break; > > - idle = do_sched_cfs_period_timer(cfs_b, overrun); > + idle = do_sched_cfs_period_timer(cfs_b, overrun, cfsb_guard.flags); > > if (++count > 3) { > u64 new, old = ktime_to_ns(cfs_b->period);