From: Joonsoo Kim <js1304@gmail.com>
To: paulmck@kernel.org
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
linux-mm@kvack.org
Subject: Re: [PATCH sl-b 1/6] mm: Add kmem_last_alloc() to return last allocation for memory block
Date: Mon, 7 Dec 2020 18:02:53 +0900 [thread overview]
Message-ID: <20201207090243.GA20765@js1304-desktop> (raw)
In-Reply-To: <20201205004057.32199-1-paulmck@kernel.org>
Hello, Paul.
On Fri, Dec 04, 2020 at 04:40:52PM -0800, paulmck@kernel.org wrote:
> From: "Paul E. McKenney" <paulmck@kernel.org>
>
> There are kernel facilities such as per-CPU reference counts that give
> error messages in generic handlers or callbacks, whose messages are
> unenlightening. In the case of per-CPU reference-count underflow, this
> is not a problem when creating a new use of this facility because in that
> case the bug is almost certainly in the code implementing that new use.
> However, trouble arises when deploying across many systems, which might
> exercise corner cases that were not seen during development and testing.
> Here, it would be really nice to get some kind of hint as to which of
> several uses the underflow was caused by.
>
> This commit therefore exposes a new kmem_last_alloc() function that
> takes a pointer to dynamically allocated memory and returns the return
> address of the call that allocated it. This pointer can reference the
> middle of the block as well as the beginning of the block, as needed
> by things like RCU callback functions and timer handlers that might not
> know where the beginning of the memory block is. These functions and
> handlers can use the return value from kmem_last_alloc() to give the
> kernel hacker a better hint as to where the problem might lie.
I agree with exposing allocation caller information to the other
subsystem to help the debugging. Some suggestions...
1. It's better to separate a slab object check (validity check) and
retrieving the allocation caller. Someone else would want to check
only a validity. And, it doesn't depend on the debug configuration so
it's not good to bind it to the debug function.
kmem_cache_valid_(obj|ptr)
kmalloc_valid_(obj|ptr)
2. rename kmem_last_alloc to ...
int kmem_cache_debug_alloc_caller(cache, obj, &ret_addr)
int kmalloc_debug_alloc_caller(obj, &ret_addr)
or debug_kmem_cache_alloc_caller()
I think that function name need to include the keyword 'debug' to show
itself as a debugging facility (enabled at the debugging). And, return
errno and get caller address by pointer argument.
3. If concrete error message is needed, please introduce more functions.
void *kmalloc_debug_error(errno)
Thanks.
next prev parent reply other threads:[~2020-12-07 9:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201205004022.GA31166@paulmck-ThinkPad-P72>
2020-12-05 0:40 ` [PATCH sl-b 1/6] mm: Add kmem_last_alloc() to return last allocation for memory block paulmck
2020-12-07 9:02 ` Joonsoo Kim [this message]
2020-12-07 17:25 ` Paul E. McKenney
2020-12-08 8:57 ` Joonsoo Kim
2020-12-08 15:17 ` Paul E. McKenney
2020-12-05 0:40 ` [PATCH sl-b 2/6] mm: Add kmem_last_alloc_errstring() to provide more kmem_last_alloc() info paulmck
2020-12-05 0:40 ` [PATCH sl-b 3/6] rcu: Make call_rcu() print allocation address of double-freed callback paulmck
2020-12-05 0:40 ` [PATCH sl-b 4/6] mm: Create kmem_last_alloc_stack() to provide stack trace in slub paulmck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201207090243.GA20765@js1304-desktop \
--to=js1304@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=dhowells@redhat.com \
--cc=edumazet@google.com \
--cc=fweisbec@gmail.com \
--cc=jiangshanlai@gmail.com \
--cc=joel@joelfernandes.org \
--cc=josh@joshtriplett.org \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=paulmck@kernel.org \
--cc=penberg@kernel.org \
--cc=peterz@infradead.org \
--cc=rcu@vger.kernel.org \
--cc=rientjes@google.com \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).