From: "Paul E. McKenney" <paulmck@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Michal Hocko <mhocko@suse.com>,
Uladzislau Rezki <urezki@gmail.com>,
LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Matthew Wilcox <willy@infradead.org>,
"Theodore Y . Ts'o" <tytso@mit.edu>,
Joel Fernandes <joel@joelfernandes.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Subject: Re: [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag
Date: Fri, 14 Aug 2020 09:11:06 -0700 [thread overview]
Message-ID: <20200814161106.GA13853@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200814141425.GM4295@paulmck-ThinkPad-P72>
On Fri, Aug 14, 2020 at 07:14:25AM -0700, Paul E. McKenney wrote:
> On Fri, Aug 14, 2020 at 10:30:37AM +0200, Peter Zijlstra wrote:
> > On Fri, Aug 14, 2020 at 01:59:04AM +0200, Thomas Gleixner wrote:
[ . . . ]
> > > > 3. Reusing existing GFP_ flags/values/whatever to communicate
> > > > the raw-context information that was to be communicated by
> > > > the new GFP_ flag.
> > > >
> > > > 4. Making lockdep forgive acquiring spinlocks while holding
> > > > raw spinlocks, but only in CONFIG_PREEMPT_NONE=y kernels.
> >
> > Uhh, !CONFIG_PREEMPT_RT, the rest is 'fine'.
>
> I would be OK with either. In CONFIG_PREEMPT_NONE=n kernels, the
> kfree_rcu() code could use preemptible() to determine whether it was safe
> to invoke the allocator. The code in kfree_rcu() might look like this:
>
> mem = NULL;
> if (IS_ENABLED(CONFIG_PREEMPT_NONE) || preemptible())
> mem = __get_free_page(...);
>
> Is your point is that the usual mistakes would then be caught by the
> usual testing on CONFIG_PREEMPT_NONE=n kernels?
Just to make sure we are talking about the same thing, please see below
for an untested patch that illustrates how I was interpreting your words.
Was this what you had in mind?
Thanx, Paul
------------------------------------------------------------------------
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 62a382d..42d0ff1 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -579,7 +579,7 @@ do { \
# define lockdep_assert_preemption_disabled() do { } while (0)
#endif
-#ifdef CONFIG_PROVE_RAW_LOCK_NESTING
+#ifdef CONFIG_PROVE_RAW_LOCK_NESTING_EFFECTIVE
# define lockdep_assert_RT_in_threaded_ctx() do { \
WARN_ONCE(debug_locks && !current->lockdep_recursion && \
diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
index bb35b44..70867d58 100644
--- a/include/linux/lockdep_types.h
+++ b/include/linux/lockdep_types.h
@@ -20,7 +20,7 @@ enum lockdep_wait_type {
LD_WAIT_FREE, /* wait free, rcu etc.. */
LD_WAIT_SPIN, /* spin loops, raw_spinlock_t etc.. */
-#ifdef CONFIG_PROVE_RAW_LOCK_NESTING
+#ifdef PROVE_RAW_LOCK_NESTING_EFFECTIVE
LD_WAIT_CONFIG, /* CONFIG_PREEMPT_LOCK, spinlock_t etc.. */
#else
LD_WAIT_CONFIG = LD_WAIT_SPIN,
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e068c3c..e02de40 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1215,6 +1215,9 @@ config PROVE_RAW_LOCK_NESTING
If unsure, select N.
+config PROVE_RAW_LOCK_NESTING_EFFECTIVE
+ def_bool PROVE_RAW_LOCK_NESTING && !PREEMPTION
+
config LOCK_STAT
bool "Lock usage statistics"
depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT
next prev parent reply other threads:[~2020-08-14 16:11 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-09 20:43 [RFC-PATCH 0/2] __GFP_NO_LOCKS Uladzislau Rezki (Sony)
2020-08-09 20:43 ` [RFC-PATCH 1/2] mm: Add __GFP_NO_LOCKS flag Uladzislau Rezki (Sony)
2020-08-10 12:31 ` Michal Hocko
2020-08-10 16:07 ` Uladzislau Rezki
2020-08-10 19:25 ` Michal Hocko
2020-08-11 8:19 ` Michal Hocko
2020-08-11 9:37 ` Uladzislau Rezki
2020-08-11 9:42 ` Uladzislau Rezki
2020-08-11 10:28 ` Michal Hocko
2020-08-11 10:45 ` Uladzislau Rezki
2020-08-11 10:26 ` Michal Hocko
2020-08-11 11:33 ` Uladzislau Rezki
2020-08-11 9:18 ` Uladzislau Rezki
2020-08-11 10:21 ` Michal Hocko
2020-08-11 11:10 ` Uladzislau Rezki
2020-08-11 14:44 ` Thomas Gleixner
2020-08-11 15:22 ` Thomas Gleixner
2020-08-12 11:38 ` Thomas Gleixner
2020-08-12 12:01 ` Uladzislau Rezki
2020-08-13 7:18 ` Michal Hocko
2020-08-11 15:33 ` Paul E. McKenney
2020-08-11 15:43 ` Thomas Gleixner
2020-08-11 15:56 ` Sebastian Andrzej Siewior
2020-08-11 16:02 ` Paul E. McKenney
2020-08-11 16:19 ` Paul E. McKenney
2020-08-11 19:39 ` Thomas Gleixner
2020-08-11 21:09 ` Paul E. McKenney
2020-08-12 0:13 ` Thomas Gleixner
2020-08-12 4:29 ` Paul E. McKenney
2020-08-12 8:32 ` Thomas Gleixner
2020-08-12 13:30 ` Paul E. McKenney
2020-08-13 7:50 ` Michal Hocko
2020-08-13 9:58 ` Uladzislau Rezki
2020-08-13 11:15 ` Michal Hocko
2020-08-13 13:27 ` Thomas Gleixner
2020-08-13 13:45 ` Michal Hocko
2020-08-13 14:32 ` Matthew Wilcox
2020-08-13 16:14 ` Thomas Gleixner
2020-08-13 16:22 ` Matthew Wilcox
2020-08-13 13:22 ` Thomas Gleixner
2020-08-13 13:33 ` Michal Hocko
2020-08-13 14:34 ` Thomas Gleixner
2020-08-13 14:53 ` Michal Hocko
2020-08-13 15:41 ` Paul E. McKenney
2020-08-13 15:54 ` Michal Hocko
2020-08-13 16:04 ` Paul E. McKenney
2020-08-13 16:13 ` Michal Hocko
2020-08-13 16:29 ` Paul E. McKenney
2020-08-13 17:12 ` Michal Hocko
2020-08-13 17:27 ` Paul E. McKenney
2020-08-13 18:31 ` peterz
2020-08-13 19:13 ` Michal Hocko
2020-08-13 16:20 ` Uladzislau Rezki
2020-08-13 16:36 ` Michal Hocko
2020-08-14 11:54 ` Uladzislau Rezki
2020-08-13 17:09 ` Thomas Gleixner
2020-08-13 17:22 ` Michal Hocko
2020-08-14 7:17 ` Michal Hocko
2020-08-14 12:15 ` Uladzislau Rezki
2020-08-14 12:48 ` Michal Hocko
2020-08-14 13:34 ` Paul E. McKenney
2020-08-14 14:06 ` Michal Hocko
2020-08-14 18:01 ` Paul E. McKenney
2020-08-14 23:14 ` Thomas Gleixner
2020-08-14 23:41 ` Paul E. McKenney
2020-08-15 0:43 ` Thomas Gleixner
2020-08-15 3:01 ` Paul E. McKenney
2020-08-15 8:27 ` Peter Zijlstra
2020-08-15 13:03 ` Paul E. McKenney
2020-08-15 8:42 ` Peter Zijlstra
2020-08-15 14:18 ` Paul E. McKenney
2020-08-15 14:23 ` Paul E. McKenney
2020-08-17 8:47 ` Michal Hocko
2020-08-13 18:26 ` peterz
2020-08-13 18:52 ` Paul E. McKenney
2020-08-13 22:06 ` peterz
2020-08-13 23:23 ` Paul E. McKenney
2020-08-13 23:59 ` Thomas Gleixner
2020-08-14 8:30 ` Peter Zijlstra
2020-08-14 10:23 ` peterz
2020-08-14 15:26 ` Paul E. McKenney
2020-08-14 14:14 ` Paul E. McKenney
2020-08-14 16:11 ` Paul E. McKenney [this message]
2020-08-14 17:49 ` Peter Zijlstra
2020-08-14 18:02 ` Paul E. McKenney
2020-08-14 19:33 ` Thomas Gleixner
2020-08-14 20:41 ` Paul E. McKenney
2020-08-14 21:52 ` Peter Zijlstra
2020-08-14 23:27 ` Paul E. McKenney
2020-08-14 23:40 ` Thomas Gleixner
2020-08-16 22:56 ` Uladzislau Rezki
2020-08-17 8:28 ` Michal Hocko
2020-08-17 10:36 ` Uladzislau Rezki
2020-08-17 22:28 ` Paul E. McKenney
2020-08-18 7:43 ` Michal Hocko
2020-08-18 13:53 ` Paul E. McKenney
2020-08-18 14:43 ` Thomas Gleixner
2020-08-18 16:13 ` Paul E. McKenney
2020-08-18 16:55 ` Thomas Gleixner
2020-08-18 17:13 ` Paul E. McKenney
2020-08-18 23:26 ` Thomas Gleixner
2020-08-19 23:07 ` Paul E. McKenney
2020-08-18 15:02 ` Michal Hocko
2020-08-18 15:45 ` Uladzislau Rezki
2020-08-18 16:18 ` Paul E. McKenney
2020-08-14 16:19 ` peterz
2020-08-14 18:15 ` Paul E. McKenney
2020-08-13 13:29 ` Uladzislau Rezki
2020-08-13 13:41 ` Michal Hocko
2020-08-13 14:22 ` Uladzislau Rezki
2020-08-09 20:43 ` [PATCH 2/2] rcu/tree: use " Uladzislau Rezki (Sony)
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