linux-kernel - Re: [PATCH v7 0/2] rcu: Dump memory object info if callback function is invalid

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Date:   Fri, 11 Aug 2023 09:07:20 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     thunder.leizhen@...weicloud.com
Cc:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Zqiang <qiang.zhang1211@...il.com>, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org, Zhen Lei <thunder.leizhen@...wei.com>
Subject: Re: [PATCH v7 0/2] rcu: Dump memory object info if callback function
 is invalid

On Sat, Aug 05, 2023 at 11:17:24AM +0800, thunder.leizhen@...weicloud.com wrote:
> From: Zhen Lei <thunder.leizhen@...wei.com>
> 
> v6 --> v7:
> To avoid snowballing, resend the two RCU-related patches that we've discussed
> OK. The remaining three patches themselves do not need to be gone into RCU tree,
> I'll send them separately for discussion.
> 
> v5 --> v6:
> 1. Use print_hex_dump() to dump the memory of slab object.
> 2. Add a new dump prefix DUMP_PREFIX_ADDRESS_LOW16
> 3. Minimize the output width of the offset
> 
> v4 --> v5:
> 1. Add Reviewed-by Acked-by for patch 1/3
> 2. Add patch 3/3:
>    mm: Dump the memory of slab object in kmem_dump_obj()
> 
> v3 --> v4:
> 1. Remove kmem_valid_obj() and convert kmem_dump_obj() to work the same way
>    as vmalloc_dump_obj().
> 2. In kernel/rcu/rcu.h
> -#include <linux/mm.h>
> +#include <linux/slab.h>
> 
> v2 --> v3:
> 1. I made statistics about the source of 'rhp'. kmem_valid_obj() accounts for
>    more than 97.5%, and vmalloc accounts for less than 1%. So change call
>    mem_dump_obj() to call kmem_dump_obj() can meet debugging requirements and
>    avoid the potential deadlock risk of vmalloc_dump_obj().
> -		mem_dump_obj(rhp);
> +		if (kmem_valid_obj(rhp))
> +			kmem_dump_obj(rhp);
> 
>    The discussion about vmap_area_lock deadlock in v2:
>    https://lkml.org/lkml/2022/11/11/493
> 
> 2. Provide static inline empty functions for kmem_valid_obj() and kmem_dump_obj()
>    when CONFIG_PRINTK=n.
> 
> v1 --> v2:
> 1. Remove condition "(unsigned long)rhp->func & 0x3", it have problems on x86.
> 2. Paul E. McKenney helped me update the commit message, thanks.
> 
> 
> Zhen Lei (2):
>   mm: Remove kmem_valid_obj()
>   rcu: Dump memory object info if callback function is invalid

Queued both on -rcu, thank you all!

							Thanx, Paul

>  include/linux/slab.h  |  5 +++--
>  kernel/rcu/rcu.h      |  7 +++++++
>  kernel/rcu/srcutiny.c |  1 +
>  kernel/rcu/srcutree.c |  1 +
>  kernel/rcu/tasks.h    |  1 +
>  kernel/rcu/tiny.c     |  1 +
>  kernel/rcu/tree.c     |  1 +
>  mm/slab_common.c      | 41 +++++++++++------------------------------
>  mm/util.c             |  4 +---
>  9 files changed, 27 insertions(+), 35 deletions(-)
> 
> -- 
> 2.34.1
>