netdev - Re: [PATCH v3 net-next 01/23] lib: add reference counting tracking infrastructure

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Date:   Wed, 15 Dec 2021 11:57:23 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Eric Dumazet <edumazet@...gle.com>,
        Jiri Slaby <jirislaby@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v3 net-next 01/23] lib: add reference counting tracking
 infrastructure


On 12/15/21 11:41, Eric Dumazet wrote:
> On Wed, Dec 15, 2021 at 2:38 AM Eric Dumazet <edumazet@...gle.com> wrote:
>>
>> On Wed, Dec 15, 2021 at 2:18 AM Jiri Slaby <jirislaby@...il.com> wrote:
>> >
>> > On 05. 12. 21, 5:21, Eric Dumazet wrote:
>> > > From: Eric Dumazet <edumazet@...gle.com>
>> > >
>> > > It can be hard to track where references are taken and released.
>> > >
>> > > In networking, we have annoying issues at device or netns dismantles,
>> > > and we had various proposals to ease root causing them.
>> > ...
>> > > --- a/lib/Kconfig
>> > > +++ b/lib/Kconfig
>> > > @@ -680,6 +680,11 @@ config STACK_HASH_ORDER
>> > >        Select the hash size as a power of 2 for the stackdepot hash table.
>> > >        Choose a lower value to reduce the memory impact.
>> > >
>> > > +config REF_TRACKER
>> > > +     bool
>> > > +     depends on STACKTRACE_SUPPORT
>> > > +     select STACKDEPOT
>> >
>> > Hi,
>> >
>> > I have to:
>> > +       select STACKDEPOT_ALWAYS_INIT
>> > here. Otherwise I see this during boot:
>> >
>>
>> Thanks, I am adding Vlastimil Babka to the CC
>>
>> This stuff has been added in
>> commit e88cc9f5e2e7a5d28a1adf12615840fab4cbebfd
>> Author: Vlastimil Babka <vbabka@...e.cz>
>> Date:   Tue Dec 14 21:50:42 2021 +0000
>>
>>     lib/stackdepot: allow optional init and stack_table allocation by kvmalloc()
>>
>>
> 
> (This is a problem because this patch is not yet in net-next, so I really do
> not know how this issue should be handled)

Looks like multiple new users of stackdepot start appearing as soon as I
touch it :)

The way we solved this with a new DRM user was Andrew adding a fixup to my
patch referenced above, in his "after-next" section of mm tree.
Should work here as well.

----8<----
>From 0fa1f25925c05f8c5c4f776913d84904fb4c03a1 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@...e.cz>
Date: Wed, 15 Dec 2021 11:52:10 +0100
Subject: [PATCH] lib/stackdepot: allow optional init and stack_table
 allocation by kvmalloc() - fixup4

Due to 4e66934eaadc ("lib: add reference counting tracking infrastructure")
landing recently to net-next adding a new stack depot user in lib/ref_tracker.c
we need to add an appropriate call to stack_depot_init() there as well.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 include/linux/ref_tracker.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index c11c9db5825c..60f3453be23e 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -4,6 +4,7 @@
 #include <linux/refcount.h>
 #include <linux/types.h>
 #include <linux/spinlock.h>
+#include <linux/stackdepot.h>
 
 struct ref_tracker;
 
@@ -26,6 +27,7 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 	spin_lock_init(&dir->lock);
 	dir->quarantine_avail = quarantine_count;
 	refcount_set(&dir->untracked, 1);
+	stack_depot_init();
 }
 
 void ref_tracker_dir_exit(struct ref_tracker_dir *dir);
-- 
2.34.1