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From:   Waiman Long <llong@redhat.com>
Subject: Re: [RFC PATCH v1 1/3] locking/lockdep: Fix false warning of
 check_wait_context()
To:     Xiongwei Song <sxwjean@me.com>, peterz@infradead.org,
        mingo@redhat.com, will@kernel.org, boqun.feng@gmail.com
Cc:     linux-kernel@vger.kernel.org, Xiongwei Song <sxwjean@gmail.com>
References: <20210711141430.896595-1-sxwjean@me.com>
Message-ID: <07878d21-fa4d-fbf5-a292-b71c48847a5e@redhat.com>
Date:   Sun, 11 Jul 2021 12:43:11 -0400
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On 7/11/21 10:14 AM, Xiongwei Song wrote:
> From: Xiongwei Song <sxwjean@gmail.com>
>
> We now always get a "Invalid wait context" warning with
> CONFIG_PROVE_RAW_LOCK_NESTING=y, see the full warning below:
>
> 	[    0.705900] =============================
> 	[    0.706002] [ BUG: Invalid wait context ]
> 	[    0.706180] 5.13.0+ #4 Not tainted
> 	[    0.706349] -----------------------------

I believe the purpose of CONFIG_PROVE_RAW_LOCK_NESTING is experimental 
and it is turned off by default. Turning it on can cause problem as 
shown in your lockdep splat. Limiting it to just PREEMPT_RT will defeat 
its purpose to find potential spinlock nesting problem in non-PREEMPT_RT 
kernel. The point is to fix the issue found, not hiding it from appearing.

Cheers,
Longman