linux-kernel - Re: [PATCH 1/1] rcu/kvfree: Add debug check of GP ready for ptrs in a list

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Wed, 5 Apr 2023 11:10:39 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        RCU <rcu@...r.kernel.org>, quic_neeraju@...cinc.com,
        Boqun Feng <boqun.feng@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH 1/1] rcu/kvfree: Add debug check of GP ready for ptrs in
 a list

On Tue, Apr 04, 2023 at 05:00:13PM -0700, Paul E. McKenney wrote:
> On Tue, Apr 04, 2023 at 04:13:00PM +0200, Uladzislau Rezki (Sony) wrote:
> > Triiger a warning if a grace period is not passed yet for
> > objects queued on a linked list via rcu_head structures.
> > 
> > Once detached, take a full snapsot of GP sequnces to check
> > later that a grace period is passed and it is safe to free
> > all pointers.
> > 
> > Based on latest 'dev' branch.
> > 
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> 
> Very good, thank you!
> 
> I queued the patch wordsmithed as shown below for review and further
> testing.  Please check for any errors.
> 
> How should we go about testing this code?  The way that it would get
> exercised in production would be during an out-of-memory event, correct?
> 
Either by flooding kfree_rcu() calls by many threads or simulate a
low memory condition. I applied i high pressure using 1 000 000 frees
by 64 kthreads on 64 CPUs system.

IMHO, we have two GP checks, one for bulk and another one for list
and it looks like enough at least from my point of view.

--
Uladzislau Rezki