From: Joel Fernandes <joel@joelfernandes.org>
To: paulmck@kernel.org
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com, rostedt@goodmis.org, hch@lst.de,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
"Michał Mirosław" <mirq-linux@rere.qmqm.pl>,
"Dmitry Osipenko" <dmitry.osipenko@collabora.com>,
"Sachin Sant" <sachinp@linux.ibm.com>,
"Zhang, Qiang1" <qiang1.zhang@intel.com>
Subject: Re: [PATCH rcu 04/20] srcu: Begin offloading srcu_struct fields to srcu_update
Date: Mon, 3 Apr 2023 21:16:27 -0400 [thread overview]
Message-ID: <CAEXW_YS-b-NyAQAR1kRy__QNo8sjHc0oYavLGqGbjitQvU7OCg@mail.gmail.com> (raw)
In-Reply-To: <bad21a93-6d1d-4069-b84b-d3dc1a6cf456@paulmck-laptop>
On Mon, Apr 3, 2023 at 9:06 PM Paul E. McKenney <paulmck@kernel.org> wrote:
[..]
> > In other words, if init_srcu_struct_nodes() returns false, then passing along
> > the return value of init_srcu_struct_nodes() back to the caller of
> > init_srcu_struct_fields() depends on whether is_static = true or false. That
> > seems a bit wrong to me, init_srcu_struct_fields() should always return
> > -ENOMEM when init_srcu_struct_nodes() fails to allocate memory IMHO, whether
> > is_static is true or not.
> >
> > Sorry if I missed something subtle, and if the code is correct to begin with.
> > Also I feel the return paths could be made better to also fix the above issue
> > I mentioned. How about the following diff on top of the series, would it
> > work?
>
> Your restructuring looks like an excellent step forward, but given the late
> date, it might be best to avoid being in a rush.
>
> I -could- make the following small patch:
>
> if (READ_ONCE(ssp->srcu_sup->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
> if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) {
> if (!ssp->srcu_sup->sda_is_static) {
> free_percpu(ssp->sda);
> ssp->sda = NULL;
> kfree(ssp->srcu_sup);
> }
> return -ENOMEM;
> } else {
> WRITE_ONCE(ssp->srcu_sup->srcu_size_state, SRCU_SIZE_BIG);
> }
> }
>
> Except that this is a pre-existing bug that as far as we know no one
> is hitting, so the risk doesn't seem to stack up. After all, if you
> are hitting memory exhaustion at boot or on module load, this bug is
> probably the least of your problems. Even this fix looks to be v6.5
> material to me.
>
> So would you be willing to send a patch like the above that fixes the
> bug, and another like you have below to get a better error-path
> structure? No hurry, the end of this month is perfectly fine.
Yes, I am happy to send patches along these lines by the end of the
month. I will make a note to do so.
> And again, good catch!
Thanks!
- Joel
next prev parent reply other threads:[~2023-04-04 1:16 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-30 22:47 [PATCH rcu 0/20] Further shrink srcu_struct to promote cache locality Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 01/20] rcu-tasks: Fix warning for unused tasks_rcu_exit_srcu Paul E. McKenney
2023-03-31 11:58 ` Frederic Weisbecker
2023-03-31 18:35 ` Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 02/20] srcu: Add whitespace to __SRCU_STRUCT_INIT() & __DEFINE_SRCU() Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 03/20] srcu: Use static init for statically allocated in-module srcu_struct Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 04/20] srcu: Begin offloading srcu_struct fields to srcu_update Paul E. McKenney
2023-04-04 0:35 ` Joel Fernandes
2023-04-04 1:06 ` Paul E. McKenney
2023-04-04 1:16 ` Joel Fernandes [this message]
2023-03-30 22:47 ` [PATCH rcu 05/20] srcu: Move ->level from srcu_struct to srcu_usage Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 06/20] srcu: Move ->srcu_size_state " Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 07/20] srcu: Move ->srcu_cb_mutex " Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 08/20] srcu: Move ->lock initialization after srcu_usage allocation Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 09/20] srcu: Move ->lock from srcu_struct to srcu_usage Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 10/20] srcu: Move ->srcu_gp_mutex " Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 11/20] srcu: Move grace-period fields " Paul E. McKenney
2023-06-01 11:14 ` Jon Hunter
[not found] ` <CALm+0cVXGdLNQpfJxnAnq2j2Ybs_rVAEqNzxgLSq7bDJp1KnfA@mail.gmail.com>
2023-06-01 13:46 ` Paul E. McKenney
2023-06-01 17:14 ` Jon Hunter
2023-06-01 19:21 ` Paul E. McKenney
2023-06-02 2:52 ` Z qiang
2023-06-02 3:09 ` Paul E. McKenney
2023-06-04 9:53 ` Linux regression tracking #adding (Thorsten Leemhuis)
2023-03-30 22:47 ` [PATCH rcu 12/20] srcu: Move heuristics " Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 13/20] srcu: Move ->sda_is_static " Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 14/20] srcu: Move srcu_barrier() fields " Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 15/20] srcu: Move work-scheduling " Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 16/20] srcu: Check for readers at module-exit time Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 17/20] srcu: Fix long lines in srcu_get_delay() Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 18/20] srcu: Fix long lines in cleanup_srcu_struct() Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 19/20] srcu: Fix long lines in srcu_gp_end() Paul E. McKenney
2023-03-30 22:47 ` [PATCH rcu 20/20] srcu: Fix long lines in srcu_funnel_gp_start() Paul E. McKenney
2023-04-04 13:57 ` [PATCH rcu 0/20] Further shrink srcu_struct to promote cache locality Joel Fernandes
2023-04-04 14:09 ` Paul E. McKenney
2023-04-04 17:01 ` Joel Fernandes
2023-04-04 17:17 ` Paul E. McKenney
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