linux-kernel - Re: [RFC] lockdep: Put graph lock/unlock under lock

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Message-ID: <20201113115416.GY2611@hirez.programming.kicks-ass.net>
Date:   Fri, 13 Nov 2020 12:54:16 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [RFC] lockdep: Put graph lock/unlock under lock_recursion
 protection

On Fri, Nov 13, 2020 at 07:05:03PM +0800, Boqun Feng wrote:
> A warning was hit when running xfstests/generic/068 in a Hyper-V guest:
> 
> [...] ------------[ cut here ]------------
> [...] DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())
> [...] WARNING: CPU: 2 PID: 1350 at kernel/locking/lockdep.c:5280 check_flags.part.0+0x165/0x170
> [...] ...
> [...] Workqueue: events pwq_unbound_release_workfn
> [...] RIP: 0010:check_flags.part.0+0x165/0x170
> [...] ...
> [...] Call Trace:
> [...]  lock_is_held_type+0x72/0x150
> [...]  ? lock_acquire+0x16e/0x4a0
> [...]  rcu_read_lock_sched_held+0x3f/0x80
> [...]  __send_ipi_one+0x14d/0x1b0
> [...]  hv_send_ipi+0x12/0x30
> [...]  __pv_queued_spin_unlock_slowpath+0xd1/0x110
> [...]  __raw_callee_save___pv_queued_spin_unlock_slowpath+0x11/0x20
> [...]  .slowpath+0x9/0xe
> [...]  lockdep_unregister_key+0x128/0x180
> [...]  pwq_unbound_release_workfn+0xbb/0xf0
> [...]  process_one_work+0x227/0x5c0
> [...]  worker_thread+0x55/0x3c0
> [...]  ? process_one_work+0x5c0/0x5c0
> [...]  kthread+0x153/0x170
> [...]  ? __kthread_bind_mask+0x60/0x60
> [...]  ret_from_fork+0x1f/0x30
> 
> The cause of the problem is we have call chain lockdep_unregister_key()
> -> <irq disabled by raw_local_irq_save()> lockdep_unlock() ->
> arch_spin_unlock() -> __pv_queued_spin_unlock_slowpath() -> pv_kick() ->
> __send_ipi_one() -> trace_hyperv_send_ipi_one().
> 
> Although this particular warning is triggered because Hyper-V has a
> trace point in ipi sending, but in general arch_spin_unlock() may call
> another function having a trace point in it, so put the arch_spin_lock()
> and arch_spin_unlock() after lock_recursion protection to fix this
> problem and avoid similiar problems.
> 
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>

Works for me, thanks!