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SubjectRe: [PATCH v2] lockdep: Show address of "struct lockdep_map" at print_lock().
On Thu, Mar 29, 2018 at 07:26:52PM +0900, Tetsuo Handa wrote:
> >From 91c081c4c5f6a99402542951e7de661c38f928ab Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Date: Tue, 27 Mar 2018 19:38:33 +0900
> Subject: [PATCH v2] lockdep: Show address of "struct lockdep_map" at print_lock().
>
> 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.
>
> 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. And I want to reduce amount of output, for
> debug_show_all_locks() might print a lot.
>
> Therefore, this patch replaces "[<%px>]" for printing hlock->acquire_ip
> field with "%p" for printing hlock->instance field.
>
> [ 251.305475] 3 locks held by a.out/31106:
> [ 251.308949] #0: 00000000b0f753ba (&mm->mmap_sem){++++}, at: copy_process.part.41+0x10d5/0x1fe0
> [ 251.314283] #1: 00000000ef64d539 (&mm->mmap_sem/1){+.+.}, at: copy_process.part.41+0x10fe/0x1fe0
> [ 251.319618] #2: 00000000b41a282e (&mapping->i_mmap_rwsem){++++}, at: copy_process.part.41+0x12f2/0x1fe0
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Acked-by: David Rientjes <rientjes@google.com>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Ingo, can you merge this?

> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> ---
> 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..0233863 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)
> --
> 1.8.3.1
>

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