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Subject[PATCH] lockdep: Show address of "struct lockdep_map" at print_lock().
Date
Currently, print_lock() is printing hlock->acquire_ip field in both
"[<%px>]" and "%pS" format. But "[<%px>]" is little useful nowadays, for
we use scripts/faddr2line which receives "%pS" for finding the location
in the source code.

Since "struct lockdep_map" is embedded into lock objects, we can know
which instance of a lock object is acquired using hlock->instance field.
This will help finding which threads are causing a lock contention when
e.g. the OOM reaper failed to acquire an OOM victim's mmap_sem for read.

Thus, this patch replaces "[<%px>]" for printing hlock->acquire_ip field
with "[%px]" for printing hlock->instance field.

----------------------------------------
[ 561.490202] Out of memory: Kill process 58945 (anacron) score 0 or sacrifice child
[ 561.494119] Killed process 58945 (anacron) total-vm:123220kB, anon-rss:232kB, file-rss:4kB, shmem-rss:0kB
(...snipped...)
[ 562.208348] Out of memory: Kill process 636 (atd) score 0 or sacrifice child
[ 562.212077] Killed process 636 (atd) total-vm:25868kB, anon-rss:204kB, file-rss:0kB, shmem-rss:0kB
(...snipped...)
[ 562.944890] Out of memory: Kill process 971 (agetty) score 0 or sacrifice child
[ 562.948586] Killed process 971 (agetty) total-vm:110056kB, anon-rss:124kB, file-rss:4kB, shmem-rss:0kB
(...snipped...)
[ 563.599714] Out of memory: Kill process 116521 (a.out) score 0 or sacrifice child
[ 563.603599] Killed process 118444 (a.out) total-vm:4176kB, anon-rss:88kB, file-rss:0kB, shmem-rss:0kB
[ 564.664223] oom_reaper: unable to reap pid:118444 (a.out)
[ 564.667311]
[ 564.667311] Showing all locks held in the system:
(...snipped...)
[ 564.731611] 1 lock held by kswapd0/76:
[ 564.734415] #0: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: rmap_walk_file+0x1d9/0x2a0
(...snipped...)
[ 564.864860] 1 lock held by atd/636:
[ 564.868524] #0: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: unlink_file_vma+0x28/0x50
[ 564.874354] 1 lock held by agetty/971:
[ 564.878085] #0: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: unlink_file_vma+0x28/0x50
(...snipped...)
[ 564.977497] 1 lock held by anacron/58945:
[ 564.981365] #0: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: unlink_file_vma+0x28/0x50
(...snipped...)
[ 569.866283] 3 locks held by a.out/118444:
[ 569.869992] #0: [ffffa3b4df1c0c88] (&mm->mmap_sem){++++}, at: copy_process.part.40+0x1090/0x1fa0
[ 569.876392] #1: [ffffa3b4dfeaae48] (&mm->mmap_sem/1){+.+.}, at: copy_process.part.40+0x10b9/0x1fa0
[ 569.882393] #2: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: copy_process.part.40+0x12ad/0x1fa0
(...snipped...)
[ 581.237572] 3 locks held by a.out/121276:
[ 581.241318] #0: [ffffa3b40cd071c8] (&mm->mmap_sem){++++}, at: copy_process.part.40+0x1090/0x1fa0
[ 581.247326] #1: [ffffa3b465bb44c8] (&mm->mmap_sem/1){+.+.}, at: copy_process.part.40+0x10b9/0x1fa0
[ 581.253370] #2: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: rmap_walk_file+0x1d9/0x2a0
(...snipped...)
[ 589.357139] 1 lock held by a.out/122960:
[ 589.363224] #0: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: rmap_walk_file+0x1d9/0x2a0
(...snipped...)
[ 594.255168] 3 locks held by a.out/124002:
[ 594.258956] #0: [ffffa3b42fead008] (&mm->mmap_sem){++++}, at: copy_process.part.40+0x1090/0x1fa0
[ 594.265047] #1: [ffffa3b4e7b52308] (&mm->mmap_sem/1){+.+.}, at: copy_process.part.40+0x10b9/0x1fa0
[ 594.271051] #2: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: copy_process.part.40+0x12ad/0x1fa0
(...snipped...)
[ 594.286952] 3 locks held by a.out/124004:
[ 594.290884] #0: [ffffa3b42feac4c8] (&mm->mmap_sem){++++}, at: copy_process.part.40+0x1090/0x1fa0
[ 594.296956] #1: [ffffa3b3db86db48] (&mm->mmap_sem/1){+.+.}, at: copy_process.part.40+0x10b9/0x1fa0
[ 594.303139] #2: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: rmap_walk_file+0x1d9/0x2a0
(...snipped...)
[ 604.765878] 2 locks held by a.out/126388:
[ 604.769899] #0: [ffffa3b3c70cb988] (&mm->mmap_sem){++++}, at: __do_page_fault+0x16f/0x4d0
[ 604.775890] #1: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: rmap_walk_file+0x1d9/0x2a0
(...snipped...)
[ 614.240787] 2 locks held by a.out/128585:
[ 614.244655] #0: [ffffa3b461e1a308] (&mm->mmap_sem){++++}, at: __do_page_fault+0x16f/0x4d0
[ 614.250489] #1: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: rmap_walk_file+0x1d9/0x2a0
(...snipped...)
[ 628.863629] 2 locks held by a.out/1165:
[ 628.867533] #0: [ffffa3b438472e48] (&mm->mmap_sem){++++}, at: __do_page_fault+0x16f/0x4d0
[ 628.873570] #1: [ffffa3b4f2c52ac0] (&mapping->i_mmap_rwsem){++++}, at: rmap_walk_file+0x1d9/0x2a0
----------------------------------------

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@suse.com>
---
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 12a2805..7835233 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 "[%px]", 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)
--
1.8.3.1
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