From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: rcu@vger.kernel.org, linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
dipankar <dipankar@in.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Josh Triplett <josh@joshtriplett.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
rostedt <rostedt@goodmis.org>,
David Howells <dhowells@redhat.com>,
Eric Dumazet <edumazet@google.com>, fweisbec <fweisbec@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
"Joel Fernandes, Google" <joel@joelfernandes.org>,
linux-nvdimm@lists.01.org, dri-devel@lists.freedesktop.org,
amd-gfx@lists.freedesktop.org
Subject: Re: [PATCH RFC tip/core/rcu 0/4] Forbid static SRCU use in modules
Date: Tue, 2 Apr 2019 08:23:34 -0700 [thread overview]
Message-ID: <20190402152334.GC4102@linux.ibm.com> (raw)
In-Reply-To: <886051277.1395.1554218080591.JavaMail.zimbra@efficios.com>
On Tue, Apr 02, 2019 at 11:14:40AM -0400, Mathieu Desnoyers wrote:
> ----- On Apr 2, 2019, at 10:28 AM, paulmck paulmck@linux.ibm.com wrote:
>
> > Hello!
> >
> > This series prohibits use of DEFINE_SRCU() and DEFINE_STATIC_SRCU()
> > by loadable modules. The reason for this prohibition is the fact
> > that using these two macros within modules requires that the size of
> > the reserved region be increased, which is not something we want to
> > be doing all that often. Instead, loadable modules should define an
> > srcu_struct and invoke init_srcu_struct() from their module_init function
> > and cleanup_srcu_struct() from their module_exit function. Note that
> > modules using call_srcu() will also need to invoke srcu_barrier() from
> > their module_exit function.
>
> This arbitrary API limitation seems weird.
>
> Isn't there a way to allow modules to use DEFINE_SRCU and DEFINE_STATIC_SRCU
> while implementing them with dynamic allocation under the hood ?
Although call_srcu() already has initialization hooks, some would
also be required in srcu_read_lock(), and I am concerned about adding
memory allocation at that point, especially given the possibility
of memory-allocation failure. And the possibility that the first
srcu_read_lock() happens in an interrupt handler or similar.
Or am I missing a trick here?
Thanx, Paul
> Thanks,
>
> Mathieu
>
>
> >
> > This series consist of the following:
> >
> > 1. Dynamically allocate dax_srcu.
> >
> > 2. Dynamically allocate drm_unplug_srcu.
> >
> > 3. Dynamically allocate kfd_processes_srcu.
> >
> > These build and have been subjected to 0day testing, but might also need
> > testing by someone having the requisite hardware.
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > drivers/dax/super.c | 10 +++++-
> > drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c | 5 +++
> > drivers/gpu/drm/amd/amdkfd/kfd_process.c | 2 -
> > drivers/gpu/drm/drm_drv.c | 8 ++++
> > include/linux/srcutree.h | 19 +++++++++--
> > kernel/rcu/rcuperf.c | 40 +++++++++++++++++++-----
> > kernel/rcu/rcutorture.c | 48 +++++++++++++++++++++--------
> > 7 files changed, 105 insertions(+), 27 deletions(-)
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
>
next prev parent reply other threads:[~2019-04-02 15:23 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-02 14:28 [PATCH RFC tip/core/rcu 0/4] Forbid static SRCU use in modules Paul E. McKenney
2019-04-02 14:29 ` [PATCH RFC tip/core/rcu 1/4] dax/super: Dynamically allocate dax_srcu Paul E. McKenney
2019-04-03 18:31 ` Dan Williams
2019-04-04 21:04 ` Paul E. McKenney
2019-04-02 14:29 ` [PATCH RFC tip/core/rcu 2/4] drivers/gpu/drm: Dynamically allocate drm_unplug_srcu Paul E. McKenney
2019-04-02 16:14 ` Daniel Vetter
2019-04-02 14:29 ` [PATCH RFC tip/core/rcu 3/4] drivers/gpu/drm/amd: Dynamically allocate kfd_processes_srcu Paul E. McKenney
2019-04-02 17:40 ` Kuehling, Felix
2019-04-04 21:16 ` Paul E. McKenney
2019-04-02 14:29 ` [PATCH RFC tip/core/rcu 4/4] rcu: Forbid DEFINE{,_STATIC}_SRCU() from modules Paul E. McKenney
2019-04-02 15:14 ` [PATCH RFC tip/core/rcu 0/4] Forbid static SRCU use in modules Mathieu Desnoyers
2019-04-02 15:23 ` Paul E. McKenney [this message]
2019-04-02 15:34 ` Mathieu Desnoyers
2019-04-03 13:32 ` Paul E. McKenney
2019-04-03 14:27 ` Mathieu Desnoyers
2019-04-03 16:20 ` Paul E. McKenney
2019-04-03 19:30 ` Joel Fernandes
2019-04-05 23:28 ` Paul E. McKenney
2019-04-06 13:33 ` Joel Fernandes
2019-04-07 13:48 ` Paul E. McKenney
2019-04-06 23:06 ` Joel Fernandes
2019-04-07 13:39 ` Paul E. McKenney
2019-04-07 13:59 ` Paul E. McKenney
2019-04-07 15:46 ` Joel Fernandes
2019-04-07 17:05 ` Paul E. McKenney
2019-04-08 0:36 ` Joel Fernandes
2019-04-08 2:28 ` Paul E. McKenney
2019-04-07 19:26 ` Mathieu Desnoyers
2019-04-07 19:32 ` Joel Fernandes
2019-04-07 20:41 ` Mathieu Desnoyers
2019-04-07 21:07 ` Joel Fernandes
2019-04-08 2:27 ` Paul E. McKenney
2019-04-08 13:05 ` Mathieu Desnoyers
2019-04-08 14:22 ` Paul E. McKenney
2019-04-08 14:49 ` Mathieu Desnoyers
2019-04-08 15:46 ` Paul E. McKenney
2019-04-08 17:24 ` Mathieu Desnoyers
2019-04-09 15:40 ` Joel Fernandes
2019-04-09 15:56 ` Mathieu Desnoyers
2019-04-09 16:18 ` Joel Fernandes
2019-04-09 16:40 ` Paul E. McKenney
2019-04-09 16:45 ` Mathieu Desnoyers
2019-04-09 17:55 ` Paul E. McKenney
2019-04-09 18:04 ` Mathieu Desnoyers
2019-04-09 19:14 ` Paul E. McKenney
2019-04-02 18:40 ` Joel Fernandes
2019-04-03 13:19 ` Paul E. McKenney
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