[PATCH 0/1] lockdep: fix warning: print_lock_trace defined but not used

[PATCH 0/1] lockdep: fix warning: print_lock_trace defined but not used

[John Hubbard]

Hi,

I ran across this minor warning while building against today's linux.git.

The proposed trivial fix leaves it a little fragile from a "what if someone
adds a new call to print_lock_trace()" point of view, but I believe that it
makes the current combination of ifdefs accurate, anyway.

Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>

John Hubbard (1):
  lockdep: fix warning: print_lock_trace defined but not used

 kernel/locking/lockdep.c | 3 +++
 1 file changed, 3 insertions(+)

-- 
2.21.0

[PATCH] lockdep: fix warning: print_lock_trace defined but not used

[John Hubbard]

Commit 0d2cc3b34532 ("locking/lockdep: Move valid_state() inside
CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING") moved the only usage of
print_lock_trace() that was originally outside of the CONFIG_PROVE_LOCKING
case. It moved that usage into a different case: CONFIG_PROVE_LOCKING &&
CONFIG_TRACE_IRQFLAGS. That leaves things not symmetrical, and as a result,
the following warning fires on my build, when I have

!CONFIG_TRACE_IRQFLAGS && !CONFIG_PROVE_LOCKING

set:

kernel/locking/lockdep.c:2821:13: warning: ‘print_lock_trace’ defined
    but not used [-Wunused-function]

Fix this by only defining print_lock_trace() in cases in which is it
called.

Fixes: 0d2cc3b34532 ("locking/lockdep: Move valid_state() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING")
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 kernel/locking/lockdep.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index d06190fa5082..3065dc36c27a 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2817,11 +2817,14 @@ static inline int validate_chain(struct task_struct *curr,
 	return 1;
 }
 
+#if defined(CONFIG_TRACE_IRQFLAGS)
 static void print_lock_trace(struct lock_trace *trace, unsigned int spaces)
 {
 }
 #endif
 
+#endif
+
 /*
  * We are building curr_chain_key incrementally, so double-check
  * it from scratch, to make sure that it's done correctly:
-- 
2.21.0

[PATCH 0/1] lockdep: fix warning: print_lock_trace defined but not used

[john.hubbard]

From: John Hubbard <jhubbard@nvidia.com>

Hi,

This is a second attempt to send this. The first attempt [1]
went via mailgw.nvidia.com, and did not receive a DKIM signature,
so I think it probably got discarded by many systems.

This one goes via gmail, which is what I was using before. We'll keep
working on getting the NVIDIA outgoing email servers working
with mailing lists, but meanwhile I'm back to using "envelope"
techniques, I guess. I was hoping to use a "native" email
address, but not quite there yet. :)

Anyway, here's the original cover letter:

I ran across this minor warning while building against today's linux.git.

The proposed trivial fix leaves it a little fragile from a "what if someone
adds a new call to print_lock_trace()" point of view, but I believe that it
makes the current combination of ifdefs accurate, anyway.

[1] https://lkml.org/lkml/2019/5/19/60

Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>

John Hubbard (1):
  lockdep: fix warning: print_lock_trace defined but not used

 kernel/locking/lockdep.c | 3 +++
 1 file changed, 3 insertions(+)

-- 
2.21.0