From b3c39758c8a6972f02b43f83dba7fe7a352371b9 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Tue, 27 Mar 2018 19:41:41 +0900 Subject: [PATCH] lockdep: Make the lock debug output more useful The lock debug output in print_lock() has a few shortcomings: - It prints the hlock->acquire_ip field in %px and %pS format. That's redundant information. - It lacks information about the lock object itself. The lock class is not helpful to identify a particular instance of a lock. Change the output so it prints: - hlock->instance to allow identification of a particular lock instance. - only the %pS format of hlock->ip_acquire which is sufficient to decode the actual code line with faddr2line. The resulting output is: 3 locks held by a.out/31106: #0: 00000000b0f753ba (&mm->mmap_sem){++++}, at: copy_process.part.41+0x10d5/0x1fe0 #1: 00000000ef64d539 (&mm->mmap_sem/1){+.+.}, at: copy_process.part.41+0x10fe/0x1fe0 #2: 00000000b41a282e (&mapping->i_mmap_rwsem){++++}, at: copy_process.part.41+0x12f2/0x1fe0 [ tglx: Massaged changelog ] Signed-off-by: Tetsuo Handa Signed-off-by: Thomas Gleixner Acked-by: Michal Hocko Acked-by: David Rientjes Acked-by: Peter Zijlstra Cc: linux-mm@kvack.org Cc: Borislav Petkov Link: https://lkml.kernel.org/r/201803271941.GBE57310.tVSOJLQOFFOHFM@I-love.SAKURA.ne.jp --- kernel/locking/lockdep.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 12a2805dd64a..023386338269 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -556,9 +556,9 @@ static void print_lock(struct held_lock *hlock) return; } + printk(KERN_CONT "%p", hlock->instance); print_lock_name(lock_classes + class_idx - 1); - printk(KERN_CONT ", at: [<%px>] %pS\n", - (void *)hlock->acquire_ip, (void *)hlock->acquire_ip); + printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip); } static void lockdep_print_held_locks(struct task_struct *curr)