linux-kernel - Re: [PATCH rcu 1/9] rcu: Add lockdep_assert_in_rcu_read

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Message-ID: <ea5341a5-a5c6-4214-96c3-32d668ce3f11@oss.qualcomm.com>
Date: Thu, 20 Feb 2025 15:51:50 -0800
From: Jeff Johnson <jeff.johnson@....qualcomm.com>
To: paulmck@...nel.org
Cc: rcu@...r.kernel.org, linux-kernel@...r.kernel.org, kernel-team@...a.com,
        rostedt@...dmis.org, Jens Axboe <axboe@...nel.dk>,
        ath12k@...ts.infradead.org
Subject: Re: [PATCH rcu 1/9] rcu: Add lockdep_assert_in_rcu_read_lock() and
 friends

On 2/20/2025 2:04 PM, Paul E. McKenney wrote:
> On Thu, Feb 20, 2025 at 11:38:14AM -0800, Jeff Johnson wrote:
>> On 6/4/24 15:23, Paul E. McKenney wrote:
>>> There is no direct RCU counterpart to lockdep_assert_irqs_disabled()
>>> and friends.  Although it is possible to construct them, it would
>>> be more convenient to have the following lockdep assertions:
>>>
>>> lockdep_assert_in_rcu_read_lock()
>>> lockdep_assert_in_rcu_read_lock_bh()
>>> lockdep_assert_in_rcu_read_lock_sched()
>>> lockdep_assert_in_rcu_reader()
>>>
>>> This commit therefore creates them.
>>
>> I'm looking at some downstream code that is trying to become
>> upstream compliant, and currently that code uses:
>>
>> 	RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "some message");
>>
>> It seems like this would be a good use of one of these helper
>> functions, but I'm shocked to see that no upstream code is using
>> them yet.
>>
>> Is there a reason to not use these helpers?
> 
> In cases where there is no additional useful information that can be
> placed in "some message", the new helpers should be just fine.

Thanks for the confirmation, Paul!

/jeff