linux-kernel - kernel/locking/lockdep.c:2877-2887: dead code

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Message-ID: <7beb0d2d.12bea.18842d18f9d.Coremail.sunying@nj.iscas.ac.cn>
Date:   Mon, 22 May 2023 17:36:50 +0800 (GMT+08:00)
From:   sunying@...iscas.ac.cn
To:     peterz@...radead.org, mingo@...hat.com, will@...nel.org
Cc:     linux-kernel@...r.kernel.org
Subject: kernel/locking/lockdep.c:2877-2887: dead code

Analyzing the preprocessed statement #ifdef in the kernel/locking/lockdep.c shows that 
the functions “check_irq_usage” and “usage_skip” at lines 2877-2887 are defined valid only
under the “CONFIG_PROVE_LOCKING &amp;&amp; !(CONFIG_TRACE_IRQFLAGS)” is true.

However, according to the configuration item "CONFIG_PROVE_LOCKING" defined in lib/Kconfig.debug, we can see:
config PROVE_LOCKING
        bool "Lock debugging: prove locking correctness"
        depends on DEBUG_KERNEL &amp;&amp; LOCK_DEBUGGING_SUPPORT
        select LOCKDEP
        select DEBUG_SPINLOCK
        select DEBUG_MUTEXES if !PREEMPT_RT
        select DEBUG_RT_MUTEXES if RT_MUTEXES
        select DEBUG_RWSEMS
        select DEBUG_WW_MUTEX_SLOWPATH
        select DEBUG_LOCK_ALLOC
        select PREEMPT_COUNT if !ARCH_NO_PREEMPT
        select TRACE_IRQFLAGS
        default n

If "CONFIG_PROVE_LOCKING: is enabled, "CONFIG_TRACE_IRQFLAGS" is automatically enabled.
The above condition "CONFIG_PROVE_LOCKING &amp;&amp; !(CONFIG_TRACE_IRQFLAGS)" will never be true,
so lines 2877-2887 will never be executed.

Should the dead code of line 2877-2887 be deleted?

Best Regards
Yanjie Ren
Ying Sun